九州大学 研究者情報
論文一覧
柿本 浩一(かきもと こういち) データ更新日:2019.03.19

教授 /  応用力学研究所 新エネルギー力学部門 ナノメカニックス分野


原著論文
1. 川野 潤、寒川義裕、屋山 巴、伊藤智徳、柿本浩一、纐纈明伯, “特集 どのように結晶成長現象をモデル化するか? 解説:GaAsN気相エピキタシーにおける混晶組成の理論的検討”, 日本結晶成長学会誌, Vol.38, No.2, 128 (46)-136 (54), 2011.07.
2. Y. Miyamura, H. Harada, K. Jiptner, J. Chen, R. R. Prakash, J. Y. Li, T. Sekiguchi, T. Kojima, Y. Ohshita, A. Ogura, M. Fukuzawa, S. Nakano, B. Gao, Koichi Kakimoto, 10 cm diameter mono cast Si growth and its characterization, 15th Gettering and Defect Engineering in Semiconductor Technology, GADEST 2013
Gettering and Defect Engineering in Semiconductor Technology XV
, 10.4028/www.scientific.net/SSP.205-206.89, 89-93, 2014.01, [URL], To get the optimized condition and ideal furnace structure, we have performed seed cast growth of mono-crystalline Si by using a unidirectional solidification furnace. More than 20 ingots of 10 cm diameter and 10 cm height were grown under different growth conditions. The quality of ingots was characterized by using Fourier transform infrared spectroscopy (FTIR), infrared microscopy, scanning infrared polariscope (SIRP), X-ray topography. We have realized reduction of carbon, residual strain and extended defects, which may contribute the increase of solar cell efficiency..
3. 北嶋具教, 劉 立軍, 北村健二, 橋本良夫, 柿本浩一, 2重坩堝ACRT法における供給原料の混入過程及び融液温度への影響, 九州大学応用力学研究所所報, 2004.01.
4. Xue Feng Han, Xin Liu, Satoshi Nakano, Hirofumi Harada, Yoshiji Miyamura, Koichi Kakimoto, 3D Global Heat Transfer Model on Floating Zone for Silicon Single Crystal Growth, Crystal Research and Technology, 10.1002/crat.201700246, 2018.01, [URL], In this paper, a three-dimensional global heat transfer model to describe the floating zone of silicon single-crystal growth is proposed. The steady-state calculations considering argon gas flow, feed rod, silicon melt and crystal are carried out using open source software OpenFOAM with no assumptions of symmetry. From the global calculation, a three dimensional solid-liquid interface has been obtained. Furthermore, the cooling effect of gas flow in three dimensions is considered, and the three-dimensional current-density distribution of the inductor is calculated. By considering the asymmetrical electromagnetic field induced by the inductor, the calculations reveal a deflection of the asymmetrical solid-liquid interface..
5. Lijun Liu, Koichi Kakimoto, 3D global analysis of CZ-Si growth in a transverse magnetic field with rotating crucible and crystal, Crystal Research and Technology, 10.1002/crat.200410349, 40, 4-5, 347-351, 2005.04, [URL], Three-dimensional global simulations were carried out for a small Czochralski furnace for silicon crystal growth with a recently developed global model. The furnace is placed in a transverse magnetic field with rotating crucible and crystal. The convective, conductive and radiative heat transfers in the entire furnace were solved in a three-dimensionally conjugated way. Three-dimensional distributions of temperature and velocity were analyzed. The melt-crystal interface was found to have nearly rotational symmetry, and the azimuthal non-uniformity of temperature is much weaker on the crystal and crucible sidewalls in the case of high rotation rates of crucible and crystal than in the case of non-rotating crucible and crystal..
6. Lijun Liu, Koichi Kakimoto, 3D global analysis of CZ-Si growth in a transverse magnetic field with various crystal growth rates, Journal of Crystal Growth, 10.1016/j.jcrysgro.2004.11.185, 275, 1-2, E1521-E1526, 2005.02, [URL], A series of computations were performed for Czochralski silicon crystal growth in a transverse magnetic field with different crystal growth rates by using a recently developed three-dimensional global model. The effects of the transverse magnetic field and crystal growth rate on the melt-crystal interface were numerically investigated. It was found that the interface shape is three-dimensional when the crystal is not rotating, while it becomes nearly two-dimensional when the crystal is rotating, even at a low rotation rate. The temperature gradient in the axial direction at the melt-crystal interface increases with increase in crystal growth rate except near the crystal edge, where it changes oppositely..
7. X. J. Chen, S. Nakano, Koichi Kakimoto, 3D numerical analysis of the influence of material property of a crucible on stress and dislocation in multicrystalline silicon for solar cells, Journal of Crystal Growth, 10.1016/j.jcrysgro.2010.10.067, 318, 1, 259-264, 2011.03, [URL], We carried out calculations to investigate the influence of thermal conductivity of the wall of a crucible on thermal stress and dislocations in a silicon ingot during a solidification process using a three-dimensional global analysis. It was found that the mc interface shape and the temperature gradient in a silicon ingot have significant influence on thermal stress and dislocations due to different thermal conductivity of the wall of a crucible. Therefore, we should control not only the mc interface shape, but also temperature gradient in a silicon ingot in order to reduce thermal stress and dislocations in a silicon ingot during a solidification process..
8. Xue Feng Han, Xin Liu, Satoshi Nakano, Hirofumi Harada, Yoshiji Miyamura, Koichi Kakimoto, 3D numerical simulation of free surface shape during the crystal growth of floating zone (FZ) silicon, Journal of Crystal Growth, 10.1016/j.jcrysgro.2017.12.012, 483, 269-274, 2018.02, [URL], In FZ growth processes, the stability of the free surface is important in the production of single crystal silicon with high quality. To investigate the shape of the free surface in the FZ silicon crystal growth, a 3D numerical model that included gas and liquid phases was developed. In this present study, 3D Young-Laplacian equations have been solved using the Volume of Fluid (VOF) Model. Using this new model, we predicted the 3D shape of the free surface in FZ silicon crystal growth. The effect of magnetic pressure on shape of free surface has been considered. In particular, the free surface of the eccentric growth model, which could not be previously solved using the 2D Young-Laplacian equations, was solved using the VOF model. The calculation results are validated by the experimental results..
9. Takashi Sekiguchi, Yoshiji Miyamura, Hirofumi Harada, Karolin Jiptner, Jun Chen, Ronit R. Prakash, Satoshi Nakano, BING GAO, Koichi Kakimoto, 50 cm size Seed Cast Si ingot growth and its characterization, Solid State Phenomena, doi:10.4028/www.scientific.net/SSP.242.30, Vol. 242, (2016), 30-34, 2015.06.
10. Yi Kyung-Woo, Shin Nakamura, Taketoshi Hibiya, Koichi Kakimoto, A numerical study of the effect of Coriolis force on the fluid flow and heat transfer due to wire heating on centrifuge, International Journal of Heat and Mass Transfer, 10.1016/0017-9310(94)90066-3, 37, 12, 1773-1781, 1994.01, [URL], The effects of the Coriolis force on a flow field, and on temperature increase during transient hot-wire heating, were studied by three-dimensional and time-dependent calculation as compared to the experimental result. We have found that the Coriolis force drastically changes the flow field as well as the heat transfer tendencies of mercury on a centrifuge. The origin of these changes is that the Coriolis force reduces the component of velocity parallel to the effective gravity, and increases the radial and azimuthal components normal to the direction of the effective gravity on the centrifuge. The order of the effect of the Coriolis force depends on the configuration and the characteristic length of the specimen..
11. 柿本浩一、北村健二, ACRT法における融液攪拌効果の解析, 日本結晶成長学会誌, Vol.29 No.2, 2002.01.
12. 北嶋 具教、 柿本 浩一, ACRT法を用いた時のLiNbO3の流動解析, 第52回理論応用力学講演会講演論文集, pp529-530, 2003.01.
13. Hubert Valencia, Yoshihiro Kangawa, Koichi Kakimoto, Ab initio model for GaAs1%xNx chemical beam epitaxy using GaAs(100) surface stability over As2, H2, and N2, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.7567/JJAP.56.060306, 56, 6, 2017.06, [URL], A model for the chemical beam epitaxy (CBE) of GaAs1%xNx was previously constructed on the basis of first-principles calculations of (100) surfaces of GaAs with As2 and H2 adsorptions and As/N substitution to simulate As2, H2, and N2 mixed gas conditions. We previously demonstrated that this model can be used to predict the temperature and pressure dependences of the growth behavior in metal-organic chemical vapor deposition (MOCVD). In this paper, we show that little modification is needed to transpose this model to CBE experiments. Our model allows us to predict transition temperatures at which Arrhenius regimes of N2 incorporation are changed. Additionally, an explanation of the trend of resulting regimes is given, which is based on the analysis of surface stability during growth at different temperatures..
14. Hubert Valencia, Yoshihiro Kangawa, Koichi Kakimoto, Ab initio study of GaAs(100) surface stability over As2, H2 and N2 as a model for vapor-phase epitaxy of GaAs1-xNx, Journal of Crystal Growth, 10.1016/j.jcrysgro.2015.09.005, 432, 6-14, 2015.12, [URL], GaAs(100) c(4×4) surfaces were examined by ab initio calculations, under As2, H2 and N2 gas mixed conditions as a model for GaAs1-xNx vapor-phase epitaxy (VPE) on GaAs(100). Using a simple model consisting of As2 and H2 molecules adsorptions and As/N atom substitutions, it was shown to be possible to examine the crystal growth behavior considering the relative stability of the resulting surfaces against the chemical potential of As2, H2 and N2 gases. Such simple model allows us to draw a picture of the temperature and pressure stability domains for each surfaces that can be linked to specific growth conditions, directly. We found that, using this simple model, it is possible to explain the different N-incorporation regimes observed experimentally at different temperatures, and to predict the transition temperature between these regimes. Additionally, a rational explanation of N-incorporation ratio for each of these regimes is provided. Our model should then lead to a better comprehension and control of the experimental conditions needed to realize a high quality VPE of GaAs1-xNx..
15. Y. Kangawa, Y. Matsuo, T. Akiyama, T. Ito, K. Shiraishi and K. Kakimoto, Ab initio-based approach on initial growth kinetics of GaN on GaN(001) , Journal of Crystal Growth, Vol.301-302, (2007)75-78., 2007.01.
16. Koichi Kakimoto, Akimasa Tashiro, Hideo Ishii, Takashige Shinozaki, Active control of melt convection of silicon by electromagnetic force under cusp-shaped magnetic fields, Materials Science in Semiconductor Processing, 10.1016/S1369-8001(02)00135-X, 5, 4-5 SPEC., 341-345, 2002.12, [URL], Three-dimensional time-dependent flow of silicon melt in an electromagnetic Czochralski system was numerically investigated. Four different positions of electrodes were taken into account to investigate the mechanism of heat and oxygen transfer in the melt under cusp-shaped magnetic fields. The results showed that the position of electrode plays an important role to control heat and oxygen transfer in silicon melt..
17. Lijun Liu, Satoshi Nakano and Koichi Kakimoto, Advancement of Numerical Investigation of a Silicon Czochralski Growth with Application of a Transverse Magnetic Field, 日本結晶成長学会誌, 2005.01.
18. Akira Kusaba, Yoshihiro Kangawa, Pawel Kempisty, Kenji Shiraishi, Koichi Kakimoto, Akinori Koukitu, Advances in modeling semiconductor epitaxy
Contributions of growth orientation and surface reconstruction to InN metalorganic vapor phase epitaxy, Applied Physics Express, 10.7567/APEX.9.125601, 9, 12, 2016.12, [URL], We propose a newly improved thermodynamic analysis method that incorporates surface energies. The new theoretical approach enables us to investigate the effects of the growth orientation and surface reconstruction. The obtained knowledge would be indispensable for examining the preferred growth conditions in terms of the contribution of the surface state. We applied the theoretical approach to study the growth processes of InN(0001) and (0001) by metalorganic vapor phase epitaxy. Calculation results reproduced the difference in optimum growth temperature. That is, we successfully developed a new theoretical approach that can predict growth processes on various growth surfaces..
19. Yoshiji Miyamura, Hirofumi Harada, Karolin Jiptner, Satoshi Nakano, Bing Gao, Koichi Kakimoto, Kyotaro Nakamura, Yoshio Ohshita, Atsushi Ogura, Shin Sugawara, Takashi Sekiguchi, Advantage in solar cell efficiency of high-quality seed cast mono Si ingot, Applied Physics Express, 10.7567/APEX.8.062301, 8, 6, 2015.01, [URL], We have grown 50 cm2 mono Si ingots by the seed cast technique. The carbon and oxygen concentrations of the ingots have been significantly reduced by improving the gas flow condition and coating. The dislocation density was also reduced by eliminating the extra dislocation generation sources. Owing to these developments, the lifetime of wafers has reached 465 μs. Finally, the efficiency of 18.7% has been achieved, which is comparable to 18.9% of the reference Czochralski (CZ) Si wafer..
20. Yoshihiro Kangawa, Koichi Kakimoto, AlN synthesis on AlN/SiC template using Li-Al-N solvent, Physica Status Solidi (A) Applications and Materials Science, 10.1002/pssa.200983566, 207, 6, 1292-1294, 2010.06, [URL], We investigated the possibility of AlN synthesis using Li-Al-N solvent. In this work, Li-Al-N solvent was obtained by heating a mixture composed of Al and Li 3N. First, we studied the relationship between Al/Li 3N composition of the initial mixture and shape of obtained crystal. The results showed that polyhedral crystals instead of needle-like crystals were obtained under an Al-rich condition, i.e., 4/33N<4/1. Next, we performed AlN synthesis on an AlN/SiC template under an Al-rich condition. The results suggested that a large AlN singlephase region was formed by using the template. The possibility of growth of bulk AlN using Li-Al-N solvent was shown by the present investigations..
21. B. Gao, S. Nakano, N. Miyazaki, Koichi Kakimoto, Alexander-haasen model of basal plane dislocations in single-crystal sapphire, Crystal Growth and Design, 10.1021/cg500705t, 14, 8, 4080-4086, 2014.08, [URL], The Alexander-Haasen model was originally used to model the multiplication of the mobile dislocations in crystalline silicon. Here, we extend this model for studying multiplication of basal plane dislocations (BPDs) in single-crystal sapphire. By fitting the Alexander-Haasen model to experimental data, we find that the model accurately describes the plastic deformation of sapphire caused by BPDs. The application of the Alexander-Haasen model to sapphire growth made it possible to minimize the dislocation density and residual stress in growing crystals by optimizing the furnace structure and operation conditions. We apply the Alexander-Haasen model to investigate the dynamical deformation of single-crystal sapphire during the cooling process and examine the effect of the cooling rate on the generation of BPDs and residual stress. Finally, we present the BPD distribution and discuss the main factor that influences the generation of BPDs..
22. Koichi Kakimoto, Atsushi Murakawa and Hideo Ishii, An Investigation of Temperature Dependence of Thermal Conductivity of Isotope Silicon, Transactions of the Materials Research Society of Japan, 2004.01.
23. Lijun Liu, Satoshi Nakano and Koichi Kakimoto, An analysis of temperature distribution near the melt-crystal interface in silicon Czochralski growth with a transverse magnetic field, Journal of Crystal Growth, 10.1016/j.jcrysgro.2005.05.002, 282, 1-2, 49-59, 2005.01.
24. Yuren Wang, Koichi Kakimoto, An in-situ X-ray topography observation of dislocations, crystal-melt interface and melting of silicon, Microelectronic Engineering, 10.1016/S0167-9317(00)00517-7, 56, 1-2, 143-146, 2001.05, [URL], An in-situ observation on the crystal-melt interfaces, their propagations and dislocations during the melting of silicon was carried out by X-ray topography technique. The dislocation-free melting process was successfully observed through the optimization of temperature distribution in the furnace and the shape of the sample. The melting with and without dislocations near the melting zone was discussed. It was demonstrated that the crystal-melt interface was kept flat during the dislocation-free melting, while the interface was rough if an isolated dislocation appeared in the melting zone..
25. Yuren Wang, Koichi Kakimoto, An in-situ observation of dislocation and crystal-melt interface during the melting silicon, Solid State Phenomena, 78-79, 217-224, Vols.78-79, pp217-224, 2001.01.
26. Atsushi Murakawa, Hideo Ishii and Koichi Kakimoto, An investigation of thermal conductivity of silicon as a function of isotope concentration by molecular dynamics, Journal of Crystal Growth, 10.1016/j.jcrysgro.2004.04.040, 267, 3-4, 452-457, 2004.07.
27. K. Kakimoto, A. Murakawa Y. Hashimoto, An investigation of thermal conductivity of isotope silicon as a function of temperature estimated by molecular dynamics, Journal of Crystal Growth, 10.1016/j.jcrysgro.2004.11.014, 275, 1-2, E427-E432, 2005.02.
28. Takahiro Kawamura, Yoshihiro Kangawa, Koichi Kakimoto, An investigation of thermal conductivity of nitride-semiconductor nanostructures by molecular dynamics simulation, Journal of Crystal Growth, Vol.298, (2007)251-253., 2006.11.
29. B. Gao, X. J. Chen, S. Nakano, Shinichi Nishizawa, Koichi Kakimoto, Analysis of SiC crystal sublimation growth by fully coupled compressible multi-phase flow simulation, Journal of Crystal Growth, 10.1016/j.jcrysgro.2010.08.032, 312, 22, 3349-3355, 2010.11, [URL], A fully coupled compressible multi-phase flow solver was developed to effectively design a large furnace for producing large-size SiC crystals. Compressible effect, convection and buoyancy effects, flow coupling between argon gas and species, and the Stefan effect are included. A small and experimental furnace is used to validate the solver. First, the essentiality of 2D flow calculation and the significance of incorporating buoyancy effect and gas convection, the Stefan effect, and flow interaction between argon gas and species were investigated by numerical results. Then the effects of argon gas on deposition rate, growth rate, graphitization on the powder source, and supersaturation and stoichiometry on the seed were analyzed. Finally, the advantages of an extra chamber design were explained, and improvement of growth rate was validated by the present solver..
30. Yoshihiro Kangawa, Koichi Kakimoto, Tomonori Ito, Akinori Koukitu, Analysis of compositional instability of InGaN by Monte Carlo simulation, Journal of Crystal Growth, 10.1016/j.jcrysgro.2006.10.017, 298, SPEC. ISS, 190-192, 2007.01, [URL], Relationships between growth conditions and atomic arrangements in InGaN thin films were investigated by Monte Carlo simulation incorporating data obtained from thermodynamic analyses and empirical interatomic potential calculations. The results suggest that compositional fluctuation was enhanced during the site-exchanging process instead of the adsorption process in the case of low indium input partial pressure. Moreover, it was found that no gross fluctuation in composition occurs but atomic-sized clustering occurs in thin films. The results agree with the experimental results [Smeeton et al., Appl. Phys. Lett. 83 (2003) 5419]..
31. Koichi Kakimoto, Bing Gao, Takuya Shiramomo, Satoshi Nakano, Shinichi Nishizawa, Analysis of growth velocity of SiC growth by the physical vapor transport method, 14th International Conference on Silicon Carbide and Related Materials 2011, ICSCRM 2011
Silicon Carbide and Related Materials 2011, ICSCRM 2011
, 10.4028/www.scientific.net/MSF.717-720.25, 25-28, 2012.05, [URL], Crystal growth velocity of SiC in a process of physical vapor transport was studied on the basis of numerical calculation including the effect of compressibility, convection and buoyancy effects, flow coupling between argon gas and species of Si, Si 2C and SiC 2, and the Stefan effect. Calculation in a 2D configuration was performed to clarify the effect of pressure on growth velocity. The results revealed that convection plays a role in the measured values that growers interpret as growth velocity based on a diffusion process of argon gas and species of Si, Si 2C and SiC 2..
32. Koichi Kakimoto, Lijun Liu, Analysis of local segregation of impurities at a silicon melt-crystal interface during crystal growth in transverse magnetic field-applied Czochralski method, Journal of Crystal Growth, 10.1016/j.jcrysgro.2009.02.041, 311, 8, 2313-2316, 2009.04, [URL], We studied local segregation of impurities, including boron, phosphorus and oxygen, at an interface between the melt and crystal during crystal growth of silicon with transverse magnetic fields. A three-dimensional global model that included local segregation based on local growth rate was used in this study. It was found that the distributions of boron and phosphorus at an interface become a saw-tooth-like pattern in the case of a small crystal rotation rate, while the distribution of oxygen concentration was almost the same at different crystal rotation rates. The distributions of boron and phosphorus were determined by segregation. However, the oxygen concentration fields in the melt and the crystal are primarily influenced by the evaporation of oxygen from the melt surface and its incorporation into the melt from the crucible wall, rather than from the segregation dynamics at the melt/crystal interface..
33. Janusz S. Szmyd, Marek Jaszczur, Hiroyuki Ozoe, Koichi Kakimoto, Analysis of natural convection with radiation from the free surface of the fluid in a vertical cylinder, JSME International Journal, Series B: Fluids and Thermal Engineering, 10.1299/jsmeb.43.679, 43, 4, 679-685, 2000.01, [URL], Three-dimensional unsteady numerical computations were carried out for buoyancy driven convection of an oxide melt (Pr = 10) and radiation from the free surface of the fluid in a vertical cylinder. The fluid was assumed to be incompressible, Newtonian and Boussinesq. Three-dimensional structures of the non-axisymmetric flow were investigated in the present study. Temperature distributions on the vertical wall of the cylinder and radiative heat transfer from the free surface of the melt were found to play a key role..
34. Hitoshi Matsuo, R. Bairava Ganesh, Satoshi Nakano, Lijun Liu, Koji Arafune, Yoshio Ohshita, Masafumi Yamaguchi, Koichi Kakimoto, Analysis of oxygen incorporation in unidirectionally solidified multicrystalline silicon for solar cells, Journal of Crystal Growth, 10.1016/j.jcrysgro.2007.12.017, 310, 7-9, 2204-2208, 2008.04, [URL], We studied the process of oxygen transfer from a quartz crucible to a multicrystalline silicon during unidirectional solidification process. We investigated the boundary layer thickness of oxygen concentration near a crucible wall region using Fourier transform infrared spectrometer (FTIR) measurement. The results suggest that oxygen concentration was increased near a crucible wall, and the boundary layer thickness of oxygen concentration was estimated to be 2-6 mm. The estimated value of boundary layer thickness of oxygen concentrations is similar to those estimated by analytical and numerical calculation. These results suggest that the oxygen was dissolved from a crucible wall through the liner made of Si3N4 to the melt during growth process..
35. Koichi Kakimoto, Lijun Liu and Satoshi Nakano, Analysis of temperature and impurity distributions in a unidirectional-solidification process for multi-crystalline silicon of solar cells by a global model, Materials Science and Engineering B, Vol.134, 269-272., 2006.06.
36. Bing Gao, Satoshi Nakano, Hirofumi Harada, Yoshiji Miyamura, Takashi Sekiguchi, Koichi Kakimoto, Anisotropic thermal stress simulation with complex crystal-melt interface evolution for seeded growth of monocrystalline silicon, Crystal Growth and Design, 10.1021/cg301225w, 12, 11, 5708-5714, 2012.11, [URL], To simulate the anisotropic thermal stress with complex crystal-melt interface evolution by the fixed-grid method during seeded growth of monocrystalline silicon, a new method that can solve the global stress field involving the crystal and melt regions without a requisite of accurate locations of the interface was proposed. The melt is regarded as a kind of hypothetical solid material that has isotropic material properties. Free boundary conditions along the crystal-melt interface are implicitly satisfied with all of the stress components inside the melt region being close to zero compared to those inside the crystal region. Therefore, regardless of the complexity of the interface shape, the stress field can be easily analyzed by a simple solver and a set of simple fixed grids even for extremely complex interface evolution. Results of numerical simulations in the isotropic, [001], and [111] growths show good consistence with other numerical and experimental results..
37. B. Gao, K. Jiptner, S. Nakano, H. Harada, Y. Miyamura, T. Sekiguchi, Koichi Kakimoto, Applicability of the three-dimensional Alexander-Haasen model for the analysis of dislocation distributions in single-crystal silicon, Journal of Crystal Growth, 10.1016/j.jcrysgro.2014.11.011, 411, 49-55, 2015.02, [URL], Applicability of the three-dimensional Alexander-Haasen (AH) model for the analysis of dislocation distributions in single-crystal silicon has been estimated. The numerical results obtained from the AH model agree well with the experimental data for both CZ-Si and FZ-Si crystals with the axis in the [001] direction but do not completely agree with the experimental data for the FZ-Si crystal with the axis in the [111] direction. The inapplicability of the AH model in a crystal with the axis in the [111] direction may arise from the neglect of dislocation propagation in this model, because the dislocation propagation in a crystal with the axis in the [111] direction is more active than that in a crystal with the axis in the [001] direction. Therefore, to increase the applicability of the AH model, it is necessary to include the effect of dislocation propagation..
38. Hiroyuki Ozoe, Koichi Kakimoto, Masato Akamatsu and Yoo Cheol Won, Application of various magnetic fields for the melt in a Czochralski
crystal growing system, 20th International Congress of Theoretical and Applied Mechanics, 2000.08.
39. K. W. Yi, Koichi Kakimoto, Z. G. Niu, M. Eguchi, H. Noguchi, S. Nakamura, K. Mukai, Asymmetric distribution of oxygen concentration in the Si melt of a Czochralski system, Journal of the Electrochemical Society, 10.1149/1.1836508, 143, 2, 722-725, 1996.01, [URL], Oxygen concentration in the Si melt of a Czochralski system was measured by immersing an oxygen sensor in the melt. The measurement clarified the existence of an inhomogeneous distribution of oxygen whose pattern was similar to the temperature distribution in the melt. This result suggests that the oxygen profile in the Si melt is not axisymmetric, although the furnace structure is axisymmetric. This oxygen fluctuation is proposed to be one reason for striations appearing in the grown crystals..
40. Koichi Kakimoto, Atomic and macroscale simulation of transport phenomena during crystal growth, 2000 IAMS International Seminar on Thermal Design and Management for Electronic Equipment and Material, pp.130-137, 2000.10.
41. Koichi Kakimoto, M. Eguchi, H. Ozoe, Bubble formation in silicon-quartz interface, Science Reports of the Research Institutes, Tohoku University, Series A: Physics, Chemistry and Metallurgy, 43, 1, 47-49, 1997, Bubble formation at an interface between silicon melt and a quartz crucible was studied by thermodynamical calculation and visualization of bubble formation using X-ray radiography. A phase diagram of silicon-oxygen (Si-O) system is also calculated from the reported thermodynamical data. Critical temperature and radius of bubble formation at the interface was discussed..
42. Jianyong Li, Ronit Roneel Prakash, Karolin Jiptner, Jun Chen, Yoshiji Miyamura, Hirofumi Harada, Koichi Kakimoto, Atsushi Ogura, Takashi Sekiguchi, Butterfly-shaped distribution of SiNx precipitates in multi-crystalline Si for solar cells, Journal of Crystal Growth, 10.1016/j.jcrysgro.2013.03.051, 377, 37-42, 2013.06, [URL], This paper concerns the precipitation mechanism of SiNx impurities in multi-crystalline silicon grown with a directional solidification system. A butterfly-shaped precipitate region was found across the middle part of ingot. These precipitates showed filament-like and fiber-like shapes of several micrometers in diameter and up to several millimeters in length. These two types of precipitates exist in different areas, forming three distribution zones in the butterfly region. The precipitate growth periodically stopped at the last stage of the butterfly formation. A non-uniform convection flow model was proposed to explain the precipitation behavior at the butterfly..
43. Koichi Kakimoto, H. Ohno, R. Katsumi, Y. Abe, H. Hasegawa, T. Katoda, CHARACTERISATION OF THERMAL INSTABILITY IN GaAs-AlAs AND GaAs-InAs SUPERLATTICES WITH LASER RAMAN SPECTROSCOPY., Institute of Physics Conference Series, 253-258, 1985, Thermal instability of GaAs-AlAs and GaAs-InAs superlattices was studied by Raman spectroscopy. Samples with various periods and grown at various temperatures were investigated to understand the stability of interface in superlattice and to obtain an activation energy of mixing by thermal annealing. Mixing occurred more easily in GaAs-InAs strained superlattice than GaAs-AlAs strain-free superlattice. Samples grown at a lower temperature are more stable against thermal annealing than those grown at a higher temperature..
44. Tomoe Yayama, Yoshihiro Kangawa, Koichi Kakimoto, Calculation of phase diagrams of the Li3N-Al system for AlN growth, Physica Status Solidi (C) Current Topics in Solid State Physics, 10.1002/pssc.201000888, 8, 5, 1581-1584, 2011.05, [URL], To investigate the possibility of AlN synthesis from Li3N and Al as source materials, a phase diagram of the Li3N-Al system was constructed by using calculation of the phase diagram (CALPHAD) method. Thermodynamic data of a ternary system was prepared on the basis of data of binary systems, which are Al-Li, Al-N and Li-N. In the present work, we newly incorporated thermodynamic data of Li3AlN2 into the system. Gibbs energy function of Li3AlN2 is described by a stoichiometric compound model and the parameter was determined to reproduce our experimental results. The calculated phase diagram was verified by differential thermal analysis (DTA). The calculated solution temperature of Li3AlN2 agreed with the DTA results and the validity was confirmed..
45. Lijun Liu, Satoshi Nakano, Koichi Kakimoto, Carbon concentration and particle precipitation during directional solidification of multicrystalline silicon for solar cells, Journal of Crystal Growth, 10.1016/j.jcrysgro.2007.11.165, 310, 7-9, 2192-2197, 2008.04, [URL], The content and uniformity of carbon and silicon carbide (SiC) precipitates have an important impact on the efficiency of solar cells made of multicrystalline silicon. We established a dynamic model of SiC particle precipitation in molten silicon based on the Si-C phase diagram. Coupling with a transient global model of heat transfer, computations were carried out to clarify the characteristics of carbon segregation and particle formation in a directional solidification process for producing multicrystalline silicon for solar cells. The effects of impurity level in silicon feedstock and solidification process conditions on the distributions of substitutional carbon and SiC precipitates in solidified silicon ingots were investigated. It was shown that the content of SiC particles precipitated in solidified ingots increases markedly in magnitude as well as in space with increase in carbon concentration in silicon feedstock when it exceeds 1.26×1017 atoms/cm3. The distribution of SiC precipitates can be controlled by optimizing the process conditions. SiC precipitates are clustered at the center-upper region in an ingot solidified in a fast-cooling process but at the periphery-upper region for a slow-cooling process..
46. Kyung Woo Yi, Masahito Watanabe, Minoru Eguchi, Koichi Kakimoto, Taketoshi Hibiya, Change in velocity in silicon melt of the czochralski (CZ) process in a vertical magnetic field, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.1143/JJAP.33.L487, 33, 4, L487-L490, 1994.01, [URL], The influence of a magnetic field on the velociry of molten silicon has been characterized both theoretically and experimentally. The velocity decrease observed by X-ray radiography in the magnetic field is in good agreement with the results obtained by numerical modelling. It is found that the rate of decrease in velocity in a vertical magnetic field is well presented using the magnetic number rather than the Hartmann number. Accordingly, the analytical expression using the square of the magnetic number, M, well describes the velociry changes as ν/ν0 = (l+M2/4)½–M/2, for experimental as well as numerically calculated data..
47. Koichi Kakimoto, Takashi Katoda, Characterization of disorder and annealing behavior of Si-implanted Ga 1-xAlx As with laser Raman spectroscopy, Journal of Applied Physics, 10.1063/1.337030, 59, 5, 1477-1481, 1986.12, [URL], Effects of aluminum in Ga1-xAlx As on damage introduced by Si implantation and annealing behavior were studied based on Raman spectra. Increase in aluminum content suppresses the introduction of damage. However, aluminum in Ga1-xAlxAs reduced the concentration of Si in lattice site after annealing..
48. Koichi Kakimoto, T. Katoda, Characterization of disordered bonds in Si-implanted Ga 0.47In0.53As with laser Raman spectroscopy, Applied Physics Letters, 10.1063/1.94104, 42, 9, 811-813, 1983, [URL], Difference in degree of disorder introduced by ion implantation into In-As and Ga-As bonds in Ga0.47In0.53As was studied with laser Raman spectroscopy. The disorder is introduced more easily into the In-As bond than into the Ga-As one. The disorder is removed simultaneously from both bonds with annealing at a temperature higher than 600°C..
49. Karolin Jiptner, Masayuki Fukuzawa, Yoshiji Miyamura, Hirofumi Harada, Koichi Kakimoto, Takashi Sekiguchi, Characterization of residual strain in Si ingots grown by the seed-cast method, 15th Gettering and Defect Engineering in Semiconductor Technology, GADEST 2013
Gettering and Defect Engineering in Semiconductor Technology XV
, 10.4028/www.scientific.net/SSP.205-206.94, 94-99, 2014.01, [URL], The residual strain distribution in cast-grown mono-like Si ingots is analyzed. The effect of the crucible during solidification and the influence of different cooling rates is described. To clarify in which process steps residual strain accumulates, several Si ingots were grown in a laboratory scale furnace (Ø100 mm) using different cooling conditions after completion of the solidification. For the cooling, two different cooling rates were distinguished: fast cooling (12°C/min) and slow cooling (5°C/min). It was found that changes in cooling gradients greatly influence the amount of residual strain. The results show that slow cooling in any temperature range leads to strain reduction. The greatest reduction could be found when the temperature gradient was changed to slow cooling in the high temperature region..
50. Hubert Valencia, Yoshihiro Kangawa, Koichi Kakimoto, Chemical beam epitaxy of GaAs1-xNx using MMHy and DMHy precursors, modeled by ab initio study of GaAs(100) surfaces stability over As2, H2 and N2, Journal of Crystal Growth, 10.1016/j.jcrysgro.2016.11.056, 468, 557-561, 2017.06, [URL], Using ab initio calculations, a simple model for GaAs1-xNx vapor-phase epitaxy on (100) surface of GaAs was created. By studying As2 and H2 molecules adsorptions and As/N atom substitutions on (100) GaAs surfaces, we obtain a relative stability diagram of all stable surfaces under varying As2, H2, and N2 conditions. We previously proved that this model could describe the vapor-phase epitaxy of GaAs1-x Nx with simple, fully decomposed, precursors. In this paper, we show that in more complex reaction conditions using monomethylhydrazine (MMHy), and dimethylhydrazine (DMHy), it is still possible to use our model to obtain an accurate description of the temperature and pressure stability domains for each surfaces, linked to chemical beam epitaxy (CBE) growth conditions. Moreover, the different N-incorporation regimes observed experimentally at different temperature can be explain and predict by our model. The use of MMHy and DMHy precursors can also be rationalized. Our model should then help to better understand the conditions needed to obtain an high quality GaAs1-xNx using vapor-phase epitaxy..
51. Koichi Kakimoto, Takashi Katoda, Clustering parameter and internal stress in iii-v ternary alloys, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.1143/JJAP.24.1022, 24, 8 R, 1022-1029, 1985, [URL], An application of laser Raman Spectroscopy to estimate the clustering parameters and internal stress accumulated in each bond in Ga0.5Al0.5As, Ga0.52ln0.48P, Ga1-xInx (0≤ x ≤ 0.53), and GaAs0.7P0.3 is proposed. The clustering parameters and stress are evaluated from the phonon intensity and the difference between the observed optical phonon frequencies and those calculated in terms of the modified REI model, respectively. The estimated values of the clustering parameter agree fairly well with those obtained from theoretical calculation of the excess free energy of mixing. The bond lengths in Ga1-xInx (0≤ x ≤ 0.53) are derived from the stress, and are compared with published data on extended X-ray absorption fine structure..
52. Xin Liu, Li Jun Liu, Yuan Wang, Koichi Kakimoto, Comparison and application of several turbulence models in simulation of crystal growth, Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics, 31, 9, 1500-1503, 2010.09, A typical industry-scale CZ furnace for growing single crystal of silicon was numerically discretized with multi-block structured grids. All heat transfer modes in the furnace, including the melt convection, solid conduction and surface radiation, are solved together in a conjugated way. To model the melt turbulence of Si in the crucible, a few turbulence models were deliberately selected and applied. These turbulence models include the low Reynolds number k-ε model, the standard k-ε model and a modified two-layer turbulence model. The simulation results obtained with these turbulence models were compared. The comparison shows that the melt flow structures predicted with these turbulence models are quite similar, while the difference in the predicted crystal-melt interface shape is obvious due to different treatment of the near wall turbulence in each model..
53. Koichi Kakimoto, Taketoshi Hibiya, Composition dependence of viscosity for molten Ga1-xAs x (0.0≤x≤0.53), Applied Physics Letters, 10.1063/1.99085, 52, 19, 1576-1577, 1988.12, [URL], Viscosity of molten Ga1-xAsx was directly measured by an oscillating cup method. The composition dependence of the synergism viscosity remarkably increases in the vicinity of stoichiometric composition; strong temperature dependence of viscosity was also observed at that composition. Activation energy for viscous flow at the stoichiometric Ga 1-xAsx (x=0.5) melt ranges from 250 to 600 meV, which was larger than those of metals such as gallium and indium whose activation energies were about 60-100 meV. We estimate, therefore, that the melt of stoichiometric composition has middle-range ordering like an aggregation whose range is larger than that of short-range ordering in metals such as gallium and indium..
54. Lijun Liu, Koichi Kakimoto, Toshinori Taishi and Keigo Hoshikawa,, Computational study of formation mechanism of impurity distribution in a silicon crystal during solidification, Journal of Crystal Growth, 10.1016/j.jcrysgro.2004.02.077, 265, 3-4, 399-409, 2004.01.
55. Lijun Liu, Xin Liu, Zaoyang Li, Koichi Kakimoto, Computer modeling of crystal growth of silicon for solar cells, Frontiers of Energy and Power Engineering in China, 10.1007/s11708-011-0155-9, 5, 3, 305-312, 2011.09, [URL], A computer simulator with a global model of heat transfer during crystal growth of Si for solar cells is developed. The convective, conductive, and radiative heat transfers in the furnace are solved together in a coupled manner using the finite volumemethod. A three-dimensional (3D) global heat transfer model with 3D features is especially made suitable for any crystal growth, while the requirement for computer resources is kept permissible for engineering applications. A structured/unstructured combined mesh scheme is proposed to improve the efficiency and accuracy of the simulation. A dynamic model for the melt-crystal (mc) interface is developed to predict the phase interface behavior in a crystal growth process. Dynamic models for impurities and precipitates are also incorporated into the simulator. Applications of the computer simulator to Czochralski (CZ) growth processes and directional solidification processes of Si crystals for solar cells are introduced. Some typical results, including the turbulent melt flow in a large-scale crucible of a CZ-Si process, the dynamic behaviors of the mc interface, and the transport and distributions of impurities and precipitates, such as oxygen, carbon, and SiC particles, are presented and discussed. The findings show the importance of computer modeling as an effective tool in the analysis and improvement of crystal growth processes and furnace designs for solar Si material..
56. Takashi Sekiguchi, Karolin Jiptner, Ronit R. Prakash, Jun Chen, Yoshiji Miyamura, Hirofumi Harada, Satoshi Nakano, Bin Gao, Koichi Kakimoto, Control of extended defects in cast and seed cast Si ingots for photovoltaic application, Physica Status Solidi (C) Current Topics in Solid State Physics, 10.1002/pssc.201400230, 12, 8, 1094-1098, 2015.08, [URL], We discuss the defect evolution in conventional cast and seed cast Si ingot growths for photovoltaic application. Three different cast Si ingots were grown in one directional solidification furnace. The two extremes are the seed cast ingots (mono-Si), where growth starts from monocrystalline silicon seeds, and the multicrystalline silicon grown from small randomly oriented grains. The conventional multicrystalline (mc-) cast Si ingots are grown without any seeds and have grain structures in between the two extremes. It was found that in mc-Si the evolution of grain boundaries take place in several steps. On the other hand, the major defects in mono-Si are dislocations and are generated by stress due to thermal gradient in the ingot..
57. K Kakimoto, Convective instability in Czochralski crystal growth system, DEVELOPMENTS IN HEAT TRANSFER, 6, 181-200, 2000.11.
58. Nobuyuki Imaishi and Koichi Kakimoto, Convective instability in Czochralski crystal growth system, Annual review on Heat Transfer, Vol.2, 187-221, 2001.12.
59. Taketoshi HIBIYA, Shin NAKAMURA, Kyung-Woo YI and Koichi KAKIMOTO , Coriolis effect on heat transfer experiment using hot-wire technique on centrifuge, Materials Procesing in High Gravity, 171-179, 1994.01.
60. Akira Nagaoka, Hideto Miyake, Tomoyasu Taniyama, Koichi Kakimoto, Kenji Yoshino, Correlation between intrinsic defects and electrical properties in the high-quality Cu2ZnSnS4 single crystal, Applied Physics Letters, 10.1063/1.4821279, 103, 11, 2013.09, [URL], Temperature dependent Hall effect measurements from 20 to 300 K have been performed on the quaternary compounds Cu2ZnSnS4 (CZTS) single crystals. The conductivity mechanisms can be described by a two-path system using Mott variable range hopping and typical thermal activation conduction. The center level of the acceptor band is 132 meV above the valence band maximum and is of width 40 meV. A correlation between the activation energy and acceptor concentration in CZTS is observed..
61. Koichi Kakimoto, Toshiyuki Shyo, Minoru Eguchi, Correlation between temperature and impurity concentration fluctuations in silicon crystals grown by the Czochralski method, Journal of Crystal Growth, 10.1016/0022-0248(95)00033-X, 151, 1-2, 187-191, 1995.05, [URL], An experiment is presented to clarify the correlation between temperature fluctuations in silicon melt and impurity concentration in grown silicon crystals. Fluctuations in temperature and concentration show a correlation in the frequency domain according to the results of fast Fourier transform analysis. The intrinsic instability of silicon convection, which includes fluctuations in temperature, affected the fluctuation in impurity concentration..
62. Koichi Kakimoto , Crucible and crystal rotation effects on oxygen distribution at an interface between solid and liquid of silicon under transverse magnetic fields, Proceedings of the Fourth Symposium on Atomic-scale Surface and Interface Dynamics, pp.89-94, 2000.03.
63. P. Rudolph, Koichi Kakimoto, Crystal Growth from the Melt under External Force Fields, MRS Bulletin, 10.1557/mrs2009.75, 34, 4, 251-258, 2009.01, [URL], The present and future demands of industrial bulk crystal growth from the melt are concentrated on improved crystal quality, increased yield, and reduced costs. To meet these challenges, the size of the melt volume must be markedly increased. As a result, violent convective perturbations appear within the melts due to turbulent heat and mass flows. They disturb the single crystal growth and give rise to compositional inhomogeneities. The application of external force fields is an effective method to dampen and control these flows. After introducing different stabilizing variants, such as constant and accelerated melt rotation, mechanical vibrations, and electric current, this article focuses on the use of magnetic fields. Nonsteady fields became very popular because, in this case, the needed strength of the magnetic induction is much lower than for steady fields. A new low-energy low-cost technology that combines heat and magnetic field generation in one module placed close to the melt crucible is introduced..
64. Y. Miyamura, H. Harada, K. Jiptner, J. Chen, R. R. Prakash, S. Nakano, B. Gao, Koichi Kakimoto, T. Sekiguchi, Crystal growth of 50 cm square mono-like Si by directional solidification and its characterization, Journal of Crystal Growth, 10.1016/j.jcrysgro.2014.03.016, 401, 133-136, 2014.09, [URL], Seed-assisted growth of mono crystalline-like Silicon (mono-like Si) ingots of 50 cm square has been performed. By controlling the shape of the liquid-solid interface, a mono-like crystal was grown from a small seed of 20 cm diameter. Several developments to reduce the carbon incorporation have been realized as can be seen from the shiny ingot surfaces. The dislocation density is reduced to the order of 104cm-2..
65. B. Gao, X.J. Chen, S. Nakano, K. Kakimoto, Crystal growth of high-purity multicrystalline silicon using a unidirectional solidification furnace for solar cells, Journal of Crystal Growth, 312, 1572-1576, 2010.04, 炭素や酸素の太陽電池の効率を低下させる軽元素の除去方法に対する新規提案を行なった。結晶成長炉内のガスの流れや化学反応を制御することにより、炭素濃度を 10^14 atom/cm3いかに低減することが可能となった。同時に、少なくとも 30%以上低減することに成功した。.
66. Koichi Kakimoto, Crystal growth of semiconductor bulk crystals, 14th International Summer School on Crystal Growth, ISSCG14
Selected Topics on Crystal Growth - 14th International Summer School on Crystal Growth, ISSCG14
, 10.1063/1.3476241, 1270, 93-106, 2010.08, [URL], This course is aimed at showing how to grow bulk crystals by using several methods. The course involves the following points. The growth methods of Bridgman and Czochralski will be introduced. The course also focuses on the mechanism of some processes with consideration of the basic phenomenon. Experimental and numerical examples of the methods will also be introduced..
67. Wang YR, Kakimoto K., Crystal-melt interface shape and dislocations during the melting of silicon, J CRYST GROWTH, 10.1016/S0022-0248(02)01833-X, 247, 1-2, 1-12, 2003.01.
68. 尾添紘之,福井英人,柿本浩一, Cz 結晶成長融液への Z 軸磁場印加効果, 電磁力を利用した材料プロセッシングの新展開(日本鉄鋼協会), pp.221-226, 1999.06.
69. Pawel Kempisty, Yoshihiro Kangawa, Akira Kusaba, Kenji Shiraishi, Stanislaw Krukowski, Michal Bockowski, Koichi Kakimoto, Hiroshi Amano, DFT modeling of carbon incorporation in GaN(0001) and GaN(000 1 ) metalorganic vapor phase epitaxy, Applied Physics Letters, 10.1063/1.4991608, 111, 14, 2017.10, [URL], The carbon incorporation mechanism in GaN(0001) and GaN(000 1) during MOVPE was investigated using density functional theory (DFT) calculations. The results confirm that the crucial factors for carbon incorporation are Fermi level pinning and accompanying surface band bending. In addition, the lattice symmetry has a strong dependence on the stability of carbon in a few subsurface layers, which results from interactions between the impurities and surface states. It was shown that these effects are responsible for facilitating or hindering the incorporation of impurities and dopants. The influence of diluent gas species (hydrogen or nitrogen) on carbon incorporation was discussed..
70. Yoichiro Ishikawa, Michio Tajima, Hirotatsu Kiuchi, Atsushi Ogura, Yoshiji Miyamura, Hirofumi Harada, Koichi Kakimoto, Determination of C concentration in P-doped n-type Czochralski-grown Si crystals by liquid N temperature photoluminescence after electron irradiation, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.7567/JJAP.57.08RB06, 57, 8, 2018.08, [URL], We demonstrated the effectiveness of photoluminescence (PL) measurement at liquid N temperature after electron irradiation for the determination of the C concentration in P-doped n-type Czochralski-grown Si crystals. The disappearance of P-related lines simplifies the spectral analysis at 77 K, enabling us to estimate the C concentration from the G-line intensity ratio regardless of the difference in P concentration. The C concentration estimated by PL measurement at 77 K was in good agreement with those by measurement PL at 4.2 K and IR absorption. Unsusceptibility to the concentration of dopant impurities is a practical advantage of the PL measurement at 77 K over that at 4.2 K..
71. Zaoyang Li, Lijun Liu, Koichi Kakimoto, Development and application of a structured/unstructured combined mesh scheme for global modeling of a directional solidification process of silicon, China Semiconductor Technology International Conference 2010, CSTIC 2010
China Semiconductor Technology International Conference 2010, CSTIC 2010
, 10.1149/1.3360749, 27, 1047-1052, 2010.12, [URL], In order to improve the accuracy and efficiency of global modeling of a directional solidification process for solar silicon, we developed a structured/unstructured combined mesh scheme. The multi-block structured mesh was used to discretize those subdomains with regular boundaries. The unstructured mesh was used to discretize those sub-domains wim highly irregular boundaries. Then it was applied in the global modeling of heat transfer for a directional solidification process to investigate the effect of argon flow rate on heat transfer and impurities transport (oxygen as an example) in the furnace. It was found that the argon flow has little effect on the global heat transfer compared with thermal radiation, while its effect on impurities transport is remarkable. The amount of oxygen carried away by the argon flow at the melt surface is closely correlated with the argon flow rate..
72. Xin Liu, Satoshi Nakano, Koichi Kakimoto, Development of carbon transport and modeling in Czochralski silicon crystal growth, Crystal Research and Technology, 10.1002/crat.201600221, 52, 1, 2017.01, [URL], In Czochralski silicon (CZ-Si) crystal growth, species generated from high temperature reactions and transported by Si melt and argon (Ar) gas strongly affect the purity and quality of the grown crystals. The reduction of carbon (C) contamination in crystal is required for producing Si wafers with long carrier lifetimes. Advances in the modeling of C contamination in CZ-Si growth are reviewed on the basis of the mass transport phenomena in the Ar gas and Si domains. The generation, incorporation, and accumulation of C were investigated by the transient global simulations of heat and mass transport during the melting process of CZ-Si growth. In addition to graphite etching, two additional sources of carbon monoxide (CO) were analyzed according to their contributions to the accumulation of C in the Si melt. The effect of gas flow control on the back diffusion of the generated CO was examined via a parametric study of the furnace pressure and the Ar gas flow rate. Strategies for C content reduction are discussed on the basis of the mechanisms of C accumulation, which indicate that the final C content depends on both the growth duration as well as the flux of contaminants at the gas/melt interface..
73. Koichi Kakimoto, Development of crystal growth technique of silicon by the Czochralski method, Acta Physica Polonica A, 10.12693/APhysPolA.124.227, 124, 2, 227-230, 2013.08, [URL], We report on the Czochralski method for single silicon crystal growth and discuss heat and mass transfer and defect formation in the crystal. A reflector was used for separation of the heating and cooling areas in the furnace enabling us to speed up crystal growth. The melt flow to stabilize the temperature distribution in a crucible was controlled using transverse magnetic fields in a large-scale silicon Czochralski furnace. The setup allows for changes in important parameters of point defect formation to be made, such as vacancies and interstitials, by changing temperature and flow fields in the furnace. A numerical calculation was developed to predict the tendency for growth of a vacancy rich or interstitial rich crystal by estimating the value of the ratio between the growth rate and temperature gradient in the crystals..
74. M. Watanabe, K. W. Yi, T. Hibiya and K. Kakimoto, Direct observation and numerical simulation of molten silicon flow during crystal growth under magnetic fields by X-ray radiography and large-scale computation, Progress in Crystal Growth and Characterization of Materials, 10.1016/S0960-8974(99)00013-3, 38, 1-4, 215-238, Vol.38, No. 1-4, pp.215-238, 1999, 1999.12.
75. Koichi Kakimoto, Minoru Eguchi, Hisao Watanabe, Taketoshi Hibiya, Direct observation by X-ray radiography of convection of molten silicon in the Czochralski growth method, Journal of Crystal Growth, 10.1016/0022-0248(88)90009-7, 88, 3, 365-370, 1988.05, [URL], Convection of molten silicon during Czochralski single crystal growth was directly observed using X-ray radiography. The melt flow pattern was monitored using a tracer method. The tracer, whose density and wettability were adjusted to that of the molten silicon, was developed. The observed convection of the molten silicon in the crucible was not only steady but also transient, and not axisymmetric but asymmetric. This asymmetry is attributed to the asymmetric temperature distribution within the crucible. The flow velocity of the molten silicon in the 75 mm diameter crucible was 10 to 20 mm/s..
76. Koichi Kakimoto, Minoru Eguchi, Hisao Watanabe, Taketoshi Hibiya, Direct observation by X-ray radiography of convection of boric oxide in the GaAs liquid encapsulated czochralski growth, Journal of Crystal Growth, 10.1016/0022-0248(89)90015-8, 94, 2, 405-411, 1989.02, [URL], Convection of molten boric oxide (B2O3) encapsulant during liquid encapsulated Czochralski single crystal growth of GaAs was directly observed by X-ray radiography. The melt flow pattern was monitored using a solid tracer method. The observed flow pattern was axisymmetric, and the flow was steady. The flow of the molten B2O3 was more stable than that of molten silicon. The flow velocity of the molten boric oxide with and without single crystal were about 0.03 and 0.3 mm/s, respectively. Numerical simulation of the molten B2O3 natural convection using commercially available code "FLUENT" was also performed. Three-dimensional calculation was carried out employing observed non-axisymmetric temperature distribution in a crucible holder. The calculated data was able to explain the steady and axisymmetric flow observed even in the non-axisymmetric temperature distribution..
77. Terutaka Goto, Hiroshi Yamada-kaneta, Yasuhiro Saito, Yuichi Nemoto, Koji Sato, Koichi Kakimoto, Shintaro Nakamura, Direct observation of vacancy in silicon using sub-Kelvin ultrasonic measurements, Materials Science and Engineering B, Vol.134,233-239., 2006.10.
78. R. Bairava Ganesh, Hitoshi Matsuo, Yoshihiro Kangawa, Koji Arafune, Yoshio Ohshita, Masafumi Yamaguchi, Koichi Kakimoto, Directional solidification of multicrystalline silicon using the accelerated crucible rotation technique, Crystal Growth and Design, 10.1021/cg800160g, 8, 7, 2525-2527, 2008.07, [URL], Employing the accelerated crucible rotation technique, we grew multicrystalline silicon by the directional solidification process. The distribution of carbon concentration determined by Fourier transform infrared spectroscopy demonstrated that application of accelerated crucible rotation homogenized the carbon concentration in the grown ingot. Attempts were made to explain the effect of crucible rotation on homogenization of carbon concentration in terms of segregation phenomena. Moreover, growth striations induced by the crucible rotation were observed in the axial direction of the ingot..
79. Bing Gao, Satoshi Nakano, Hirofumi Harada, Yoshiji Miyamura, Takashi Sekiguchi, Koichi Kakimoto, Dislocation analysis of a new method for growing large-size crystals of monocrystalline silicon using a seed casting technique, Crystal Growth and Design, 10.1021/cg301274d, 12, 12, 6144-6150, 2012.12, [URL], A new method is proposed for growing large-size crystals of monocrystalline silicon using a seed casting technique. The stress and dislocation distributions for this type of growth during crystallization were simulated. The results indicate that the order of dislocation density is not very large. If the cooling flux of the crystal growth is controlled to be small at the initial stage, and the annihilation and direction effects of dislocation in the Alexander and Haasen model are included, the real dislocation density could be considerably smaller than the calculated value. Therefore, the new growth method for monocrystalline silicon is promising for complete single crystal growth, effectively avoids polycrystalline nucleation, and has a moderate dislocation density..
80. Yuren Wang, Koichi Kakimoto, Dislocation and Crystal-melt Interface In the Melting Processes of Silicon, Proceedings of the Fifth Symposium on Atomic-scale Surface and Dynamics, pp133-140, 2001.01.
81. Karolin Jiptner, Yoshiji Miyamura, Hirofumi Harada, Bing Gao, Koichi Kakimoto, Takashi Sekiguchi, Dislocation behavior in seed-cast grown Si ingots based on crystallographic orientation, Progress in Photovoltaics: Research and Applications, 10.1002/pip.2708, 24, 12, 1513-1522, 2016.12, [URL], This study concentrates on dislocation behavior during Si growth by the seed-cast method in different crystallographic orientations. Two methods were combined: (1) Si crystal growth in different seed orientations and (2) float zone Si-annealing experiment to obtain the purely thermal stress-induced dislocation density. The main focus is on the difference between the (111) and the (100) growth directions. It is found that peripheral areas are dominated by thermal stress-induced dislocation densities. Central ingot areas are dominated by other dislocation sources. By comparing the (100) and the (111) orientations, it was found that a difference in dislocation motion exists. This difference is caused by a different activation of slip systems, causing long slip lines in the (111) orientation. It is shown that numerical simulation has problems describing this long-range dislocation slip..
82. Yuren Wang and Koichi Kakimoto, Dislocation effect on crystal-melt interface: an in situ observation of the melting of silicon, J. of Crystal Growth, 10.1016/S0022-0248(99)00406-6, 208, 1-4, 303-312, Vol.208, pp.303-312, 2000.12.
83. B. Gao, Koichi Kakimoto, Dislocation-density-based modeling of the plastic behavior of 4H-SiC single crystals using the Alexander-Haasen model, Journal of Crystal Growth, 10.1016/j.jcrysgro.2013.10.023, 386, 215-219, 2014.01, [URL], To dynamically model the plastic deformation of 4H-SiC single crystals during physical vapor transport (PVT) growth, the Alexander-Haasen model, originally proposed for the elemental semiconductor, is extended into IV-IV compound semiconductors. By fitting the model parameters to the experimental data, we show that the Alexander-Haasen model can describe the plastic deformation of 4H-SiC single crystals if the activation of the carbon-core partial dislocation is modeled in the high-temperature region (above 1000 C) and the silicon-core partial dislocation is modeled in the low-temperature region (below 1000 C). We then apply the same model to the dynamical deformation process of a 4H-SiC single crystal during PVT growth. The time evolution of the dislocation density is shown, and the effects of the cooling time on the final dislocation density, residual stress and stacking faults are also examined..
84. Yuren Wang and Koichi Kakimoto, Dislocations and crystal-melt interface in the melting prosesses of silicon, Proceedings of the fifth symposium on atomic-scale surface and interface dynamics, No. 12, March 1-2, pp.133-140, 2001.03.
85. Hitoshi Matsuo, Sho Hisamatsu, Yoshihiro Kangawa, and Koichi Kakimoto, Distributions of light elements in multicrystalline silicon for solar cells grown by directional solidification, Journal of the Electrochemical Society, Vol.156, NO.9, (2009) H711-H715.
, 2009.09.
86. H. Matsuo, S. Hisamatsu, Yoshihiro Kangawa, Koichi Kakimoto, Distributions of light elements and their precipitations grown by unidirectional solidification method in multicrystalline silicon for solar cells, ISTC/CSTIC 2009 (CISTC)
ECS Transactions - ISTC/CSTIC 2009 (CISTC)
, 10.1149/1.3096569, 18, 1037-1042, 2009, [URL], We investigated the relationship between the formation of small grains and distribution of precipitates such as Si3N4 and SiON in a multicrystalline silicon ingot grown by the unidirectional solidification method. Si3N4 precipitate was mainly observed inside the small grain region, while SiON was mainly precipitated outside there. We found that SiON started to precipitate prior to formation of Si3N 4 precipitates. Therefore, precipitation of SiON prior to precipitation of Si3N4 plays a key role in the formation of small grains..
87. Y. Miyamura, H. Harada, S. Nakano, Shinichi Nishizawa, Koichi Kakimoto, Do thermal donors reduce the lifetimes of Czochralski-grown silicon crystals?, Journal of Crystal Growth, 10.1016/j.jcrysgro.2018.02.034, 489, 1-4, 2018.05, [URL], High-performance electronics require long carrier lifetimes within their silicon crystals. This paper reports the effects of thermal donors on the lifetimes of carriers in as-grown n-type silicon crystals grown by the Czochralski method. We grew silicon crystals with two different concentrations of thermal donors using the following two cooling processes: one was cooled with a 4-h halt after detaching the crystal from the melt, and the other was cooled continuously. The crystal grown with the cooling halt contained higher concentrations of thermal donors of the order of 1 × 1013 cm−3, while the crystal without the halt had no thermal donors. The measured bulk lifetimes were in the range of 15–18 ms. We concluded that thermal donors in Czochralski-grown silicon crystals do not act to reduce their lifetimes..
88. Masahito Watanabe, Minoru Eguchi, Koichi Kakimoto, Taketoshi Hibiya, Double-beam x-ray radiography system for three-dimensional flow visualization of molten silicon convection, Journal of Crystal Growth, 10.1016/0022-0248(93)90099-I, 133, 1-2, 23-28, 1993.10, [URL], A "double-beam X-ray radiography system" is developed for three-dimensional visualization of the flow of molten silicon convection during Czochralski crystal growth. The system contains two sets of X-ray sources and X-ray cameras set at right angles to each other. Tracers are tracked in three dimensions by stereoscopic photograph theory. The new system is described in detail and three-dimensionally visualized particle paths of molten silicon convection are presented. This visualization technique shows that the azimuthal flow direction of molten silicon strongly depends on the crucible and crystal rotations rates, and they can be categorized using the relationship between the crystal and crucible Reynolds numbers..
89. Lijun Liu, Satoshi Nakano, Koichi Kakimoto, Dynamic simulation of temperature and iron distribution in a casting process for crystalline silicon solar cells with a global model, Journal of Crystal Growth, 2006.01.
90. H. Maeda, Koichi Kakimoto, M. Kikuchi, K. Watanabe, Effect of V, Ir-Doping on the Jc Properties of Bi2223 Tapes, IEEE Transactions on Applied Superconductivity, 10.1109/77.785004, 9, 2 PART 2, 2541-2544, 1999.12, [URL], We prepared Ag-sheathed mono-core tapes and multifilamentary tapes with 19 filaments by the powder-intube method, using V- and Ir- doped B12223 powder with a doping amount x less than 0.15. In the doped tapes two effects are overlapped: One is the decrease in Jc due to some weak links caused by precipitates such as Sr-V-O oxides, and the other is the increase in 3C with the doping content due to the enhancement of Bi2223 phase formation. This results in a minimum in Jc at x=0.05. The second effect becomes stronger in the V-doping, because of the great enhancement of Bi2223 phase formation. In the Ir-doped tapes the Jc values decrease monotonically with the doping content. For the multifilamentary tapes the V-doping is very effective to obtain high Ic values..
91. Xin Liu, Xue Feng Han, Satoshi Nakano, Koichi Kakimoto, Effect of controlled crucible movement on melting process and carbon contamination in Czochralski silicon crystal growth, Journal of Crystal Growth, 10.1016/j.jcrysgro.2017.12.016, 483, 241-244, 2018.02, [URL], In Czochralski silicon (CZ-Si) crystal growth, packed Si chunks experience collapse and volume shrinkage during the melting process. The axial movements of the crucible and the melting of the Si feedstock lead to dynamic thermal and flow fields and affect mass transport. To study the effect of crucible movement on the melting process and carbon (C) contamination, the cases of fixed and lifting crucible were investigated by the transient global simulation with dynamic mesh deformation. The gap width between the gas-guide and the top surface of Si feedstock was kept constant during the crucible lifting process. Impurity and species transport in Si feedstock and argon gas was investigated for the cases with the fixed and lifting crucibles. The comparison of C accumulation processes indicated that the lifting crucible case resulted in higher C contamination than that found in the fixed crucible case. Furthermore, lifting crucible cases with different gap widths were investigated to elaborate strategies for controlling the crucible movement for its effect on the melting process and C contamination in CZ-Si crystal growth. It was observed that the optimum gap width for C reduction results from the trade-off between the back diffusion and gas convection..
92. B. Gao, S. Nakano, H. Harada, Y. Miyamura, Koichi Kakimoto, Effect of cooling rate on the activation of slip systems in seed cast-grown monocrystalline silicon in the [001] and [111] directions, Crystal Growth and Design, 10.1021/cg400428z, 13, 6, 2661-2669, 2013.06, [URL], To effectively reduce dislocation by controlling the cooling process, the effect of cooling rate on the activation of slip systems was studied in seed cast-grown monocrystalline silicon in the [001] and [111] growth directions. The results show that the cooling rate has a large effect on the activation of slip systems. In the [001] growth direction, a slow cooling rate either weakly activates 4-fold symmetric slip systems or does not activate them at all. In contrast, a fast cooling rate strongly activates the 4-fold symmetric slip systems. In the [111] growth direction, a slow cooling rate weakly activates the three 3-fold symmetric slip systems, while a fast cooling rate strongly activates the three 3-fold symmetric slip systems. The differences of the activation of the slip systems between the slow and fast cooling rates mainly cause differences in dislocation and residual stress. Irrespective of the crystal growth direction, it is mainly the radial flux that causes the difference between the fast and slow cooling rates. Therefore, the most effective method for reducing dislocation during the cooling process is to decrease the radial flux..
93. B. Gao, S. Nakano, Koichi Kakimoto, Effect of crucible cover material on impurities of multicrystalline silicon in a unidirectional solidification furnace, Journal of Crystal Growth, 10.1016/j.jcrysgro.2010.10.158, 318, 1, 255-258, 2011.03, [URL], It has been suggested that the use of a crucible cover can reduce the carbon impurity of multicrystalline silicon in a unidirectional solidification furnace. The material of the cover has an obvious effect on the impurity concentration. If the cover is made from an inertia material, such as tungsten or molybdenum, the carbon impurity in multicrystalline silicon can be reduced by 1000 times compared to that in the conventional furnace; however, due to the costliness of tungsten, a cheaper material such as carbon is preferred. When a cover made from carbon is used, the carbon impurity in multicrystalline silicon can be reduced by 10 times compared to that in the conventional furnace. Therefore, an effective and economical method for reducing the carbon impurity is to design a cover made from carbon and with a thin layer of tungsten deposited on the surface..
94. S. Nakano, L. J. Liu, X. J. Chen, H. Matsuo, Koichi Kakimoto, Effect of crucible rotation on oxygen concentration in the polycrystalline silicon grown by the unidirectional solidification method, Journal of Crystal Growth, 10.1016/j.jcrysgro.2008.12.020, 311, 4, 1051-1055, 2009.02, [URL], We investigated the influence of crucible rotation on oxygen concentration in the melt using numerical analysis in the unidirectional solidification process for solar cells. The results showed that oxygen concentration in the melt using crucible rotation is higher than that without using crucible rotation. The reason is that the magnitude of decrease in the flux of oxygen evaporation from the top of the melt is larger than that of oxygen dissolution from the crucible wall to the melt in the case of high crucible rotation rate..
95. Hitoshi Matsuo, R. Bairava Ganesh, Satoshi Nakano, Lijun Liu, Koji Arafune, Yoshio Ohshita, Masafumi Yamaguchi, Koichi Kakimoto, Effect of crucible rotation on oxygen concentration during unidirectional solidification process of multicrystalline silicon for solar cells, Journal of Crystal Growth, 10.1016/j.jcrysgro.2008.11.063, 311, 4, 1123-1128, 2009.02, [URL], We studied the effects of crucible rotation on distribution of oxygen concentration in a crystal during the unidirectionally solidification process of multicrystalline silicon for solar cells. Oxygen concentration in the melt increased when crucible rotation rate was increased. Oxygen concentration in the silicon crystal was distributed inhomogeneously in the radial direction when crucible rotation rate was increased. This is due to suppression of oxygen transport. Consequently, less oxygen was transported from the crucible wall to the center of the melt. We found that oxygen concentration is small in the whole ingot and homogenized in the radial direction when crucible rotation rate during the solidification process is set to 1 rpm..
96. Wataru Fukushima, Hirofumi Harada, Yoshiji Miyamura, Masato Imai, Satoshi Nakano, Koichi Kakimoto, Effect of oxygen on dislocation multiplication in silicon crystals, Journal of Crystal Growth, 10.1016/j.jcrysgro.2017.12.030, 486, 45-49, 2018.03, [URL], This paper aims to clarify the effect of oxygen on dislocation multiplication in silicon single crystals grown by the Czochralski and floating zone methods using numerical analysis. The analysis is based on the Alexander–Haasen–Sumino model and involves oxygen diffusion from the bulk to the dislocation cores during the annealing process in a furnace. The results show that after the annealing process, the dislocation density in silicon single crystals decreases as a function of oxygen concentration. This decrease can be explained by considering the unlocking stress caused by interstitial oxygen atoms. When the oxygen concentration is 7.5 × 1017 cm−3, the total stress is about 2 MPa and the unlocking stress is less than 1 MPa. As the oxygen concentration increases, the unlocking stress also increases; however, the dislocation velocity decreases..
97. S. Kambe, Y. C. Guo, S. X. Dou, H. K. Liu, Y. Wakahara, H. Maeda, Koichi Kakimoto, M. Yavuz, Effect of pressing and Li doping on superconducting properties of Ag-sheathed Bi-2223 tapes, Superconductor Science and Technology, 10.1088/0953-2048/11/10/034, 11, 10, 1061-1064, 1998.10, [URL], For Bi-2223 Ag-sheathed tapes, pressing conditions between sintering were optimized. It was found that with an increase in the pressure from 1 t cm-2 to 10 t cm-2, lc of the tape was increased. To elucidate whether Li doping increases the lc of the tape as reported in the bulk sample, Li doping was carried out. It was found that doping of 0.1-0.3 at.% Li increased lc by 10%, which is consistent with the bulk data. As a result of lc-B measurement at a temperature of 4.2 K, it was found that lc/lc(O T) of the 0.3 at.% Li-doped tape under a magnetic flux density of 10 T was 20% higher than that of the non-doped tapes..
98. BING GAO, Koichi Kakimoto, Effect of the Inclusion of T ransparency on the Thermal Field and Interface Shape in Long-term Sublimation Growth of SiC Crystals, 日本結晶成長学会誌Vol.40, 1, 20-24, 2013.01.
99. Xin Liu, Satoshi Nakano, Koichi Kakimoto, Effect of the packing structure of silicon chunks on the melting process and carbon reduction in Czochralski silicon crystal growth, Journal of Crystal Growth, 10.1016/j.jcrysgro.2016.09.062, 468, 595-600, 2017.06, [URL], Carbon (C) contamination in Czochralski silicon (CZ-Si) crystal growth mainly originates from carbon monoxide (CO) generation on the graphite components, which reaches a maximum during the melting stage. Loading a crucible with poly-Si feedstock includes many technical details for optimization of the melting and growth processes. To investigate the effect of the packing structure of Si chunks on C accumulation in CZ-Si crystal growth, transient global simulations of heat and mass transport were performed for the melting process with different packing structures of poly-Si. The heat transport modeling took into account the effective thermal conductivity (ETC) of the Si feedstock, which is affected by the packing structure. The effect of the chunk size on the melting process and C accumulation were investigated by parametric studies of different packing structures. The heat transport and melting process in the crucible were affected by the ETC and the emissivity of the Si feedstock. It was found that smaller Si chunks packed in the upper part could speed up the melting process and smooth the power profile. Decreasing the duration of the melting process is favorable for reduction of C contamination in the Si feedstock. Parametric studies indicated that optimization of the melting process by the packing structure is possible and essential for C reduction in CZ-Si crystal growth..
100. Lijun Liu and Koichi Kakimoto, Effects of Magnetic Fields on Melt-Crystal Interface Shape and Melt Flow in Czochralski Silicon Growth, Proceedings of the 5th International Conference of Single Crystal Growth and Heat & Mass Transfer, Obninsk, Russia, 2003.01.
101. Zaoyang Li, Lijun Liu, Wencheng Ma, Koichi Kakimoto, Effects of argon flow on heat transfer in a directional solidification process for silicon solar cells, Journal of Crystal Growth, 10.1016/j.jcrysgro.2010.11.040, 318, 1, 298-303, 2011.03, [URL], A global heat transfer model, including the melt convection, argon flow, thermal conduction, thermal radiation and fully coupled boundary conditions, was developed to investigate the argon flow effect on the temperature distribution and melt convection in a directional solidification furnace for silicon solar cells. Both the effect of argon flow rate and the effect of furnace pressure were examined. It was found that the heat transfer at the melt free surface due to the gas convection cannot be neglected, though the argon flow contributes little to the global heat transfer at most radiative surfaces. The shear stress caused by the argon flow at the melt free surface becomes larger with the increase in argon flow rate and it further changes the velocity and temperature distributions in the silicon melt. We also found that the effect of argon flow on the melt convection at a low furnace pressure will be enhanced if the argon mass flow rate is kept constant. The solidification process can thus be controlled by modifying the argon flow rate and the furnace pressure..
102. Zaoyang Li, Lijun Liu, Wencheng Ma, Koichi Kakimoto, Effects of argon flow on impurities transport in a directional solidification furnace for silicon solar cells, Journal of Crystal Growth, 10.1016/j.jcrysgro.2010.11.030, 318, 1, 304-312, 2011.03, [URL], A global simulation including coupled oxygen and carbon transport was carried out to study the argon flow effects on the impurities transport in a directional solidification furnace for silicon solar cells. The simulation is based on a fully coupled calculation of the thermal and flow fields in a furnace including argon gas flow and melt convection. Five chemical reactions are considered in the impurity transport model. The effects of both the argon flow rate and the furnace pressure were examined. It was found that the argon flow has an important effect on the silicon melt convection, which will further influence the evaporation characteristic of SiO at the melt free surface. The amount of SiO carried away by the argon flow increases with increase in the argon flow rate while the CO gas can be prevented from being transported to the melt free surface. There exists a peak value for the concentration of impurities in the furnace chamber regarding argon flow rate due to the correlation among SiO evaporated, reacted and taken away. The pressure also influences the impurity transport in the furnace by modifying the pattern of argon flow. The numerical results demonstrate a method to control the oxygen and carbon transport in a directional solidification furnace by adjusting the argon flow rate and the furnace pressure..
103. Lijun Liu, Koichi Kakimoto, Effects of crystal rotation rate on the melt-crystal interface of a CZ-Si crystal growth in a transverse magnetic field, Journal of Crystal Growth, 10.1016/j.jcrysgro.2007.10.043, 310, 2, 306-312, 2008.01, [URL], A series of computations were carried out to study the effect of crystal rotation rate on the melt-crystal interface shape and temperature gradient at the interface during CZ-Si crystal growth in a transverse magnetic field (TMCZ). A three-dimensional (3D) global model was used in this study. It was found that the interface deflection changes from non-uniformity in the azimuthal direction to an axisymmetric distribution with increasing crystal rotation rate. The mechanism of this effect is mainly attributed to the spatial fluctuations of local growth rate, which is derived as a function of crystal rotation rate and non-uniformity of interface deflection in the azimuthal direction. It contributes to the formation of the shape of the melt-crystal interface through the heat release of solidification at the melt-crystal interface. Even though the melt-crystal interface shape is nearly axisymmetric at a high crystal rotation rate, local growth rate fluctuations are still noticeable and play an important role in the characteristics of heat transfer and impurity segregation at the melt-crystal interface..
104. K. Kakimoto, Effects of rotating magnetic fields on temperature and oxygen distributions in silicon melt, Journal of Crystal Growth 237-239, 10.1016/S0022-0248(01)02341-7, 237, 1785-1790, pp1785-1790, 2002.01.
105. Tomonori Kitashima, Lijun Liu, Kenji Kitamura and Koichi Kakimoto, Effects of shape of an inner crucible on convection of lithium niobate melt in a double-crucible Czochralski process using the accelerated crucible rotation technique, Journal of Crystal Growth, 10.1016/j.jcrysgro.2004.04.026, 267, 3-4, 574-582, 2004.01.
106. Akira Nagaoka, Hideto Miyake, Tomoyasu Taniyama, Koichi Kakimoto, Yoshitaro Nose, Michael A. Scarpulla, Kenji Yoshino, Effects of sodium on electrical properties in Cu2ZnSnS 4 single crystal, Applied Physics Letters, 10.1063/1.4871208, 104, 15, 2014.01, [URL], We have studied the effect of sodium on the electrical properties of Cu2ZnSnS4 (CZTS) single crystal by using temperature dependence of Hall effect measurement. The sodium substitution on the cation site in CZTS is observed from the increasing of unit-cell size by powder X-ray diffraction. Sodium increases the effective hole concentration and makes the thermal activation energy smaller. The degree of compensation decreases with sodium incorporation, thus the hole mobility is enhanced. We revealed that sodium is important dopant in CZTS to control the electrical properties..
107. Akira Nagaoka, Kenji Yoshino, Hideto Miyake, Tomoyasu Taniyama, Koichi Kakimoto, Electrical properties of Cu2ZnSnS4 single crystal, 39th IEEE Photovoltaic Specialists Conference, PVSC 2013
39th IEEE Photovoltaic Specialists Conference, PVSC 2013
, 10.1109/PVSC.2013.6745011, 2621-2624, 2013.01, [URL], Cu2ZnSnS4 (CZTS) has attracting considerable interest because first principle calculation predict that its electronic properties must be similar to chalcopyrite Cu(In, Ga)Se2 (CIGS). However, the fundamental studies of CZTS, which are single crystal growth and electrical property, are little known. Here, we report on CZTS single crystal growth from solution and electrical properties. Optimum growth condition of CZTS was determined based on CZTS-Sn phase diagram, which was growth temperature 900̊C and X= 70 mol% solution. It is shown that the conduction mechanism have two-path system (defects and band transports), which were characterized by M-VRH for the defect path and typical thermal activation conduction for band path..
108. H. Yamada-Kaneta, K. Tanahashi, K. Kakimoto and S. Suto, Enhanced diffusion of boron in silicon by cw CO2 laser irradiation, Surface and Interface Analysis, Vol.38, 1683-1686., 2006.02.
109. Hiroshi Yamada-Kaneta, Katsuto Tanahashi, Koichi Kakimoto, Shozo Suto, Enhancement of boron diffusion in silicon by continuous wave CO2 laser irradiation, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.1143/JJAP.46.5085, 46, 8 A, 5085-5088, 2007.08, [URL], We investigated the diffusion of boron (B) by the irradiation of cw CO 2 laser light. The diffusion of B was enhanced by irradiating the laser light during annealing in Ar/O2ambient. It was found that the irradiation of the laser light had the effect of enhances on the growth of an oxide layer. The possible mechanism of the enhanced diffusion is that the excess self-interstitials injected by oxidation at a laser-irradiated point assist the diffusion of B..
110. Lijun Liu, Katsutoshi Tanahashi and Hiroshi Yamada-Kaneta, Y. Kangawa and Koichi Kakimoto, Enhancement of the diffusion of oxygen and boron in silicon crystals under irradiation of infrared laser light, JOURNAL OF APPLIED PHYSICS, Vol.99, No.7, (2006) 073103 1-4., 2006.01.
111. R. Bairava Ganesh, Hitoshi Matsuo, Takahiro Kawamura, Yoshihiro Kangawa, Koji Arafune, Yoshio Ohshita, Masafumi Yamaguchi, Koichi Kakimoto, Estimation of growth rate in unidirectionally solidified multicrystalline silicon by the growth-induced striation method, Journal of Crystal Growth, 10.1016/j.jcrysgro.2008.01.049, 310, 11, 2697-2701, 2008.05, [URL], Multicrystalline silicon was grown by unidirectional solidification method using the accelerated crucible rotation technique. The application of the accelerated crucible rotation technique in unidirectional solidification method induced growth striations across the axial direction of the grown crystal. This striation pattern was observed from carbon concentration distribution, obtained by using Fourier transform infrared spectroscopy. The generated striation pattern was found to be weak and discontinuous. Some striations were absent, probably due to back melting, caused during each crucible rotation. From the growth striations and applied time period in crucible rotation, the growth rate was estimated by using Fourier transformation analysis..
112. Tomihisa Tachibana, Takashi Sameshima, Takuto Kojima, Koji Arafune, Koichi Kakimoto, Yoshiji Miyamura, Hirofumi Harada, Takashi Sekiguchi, Yoshio Ohshita, Atsushi Ogura, Evaluation of defects generation in crystalline silicon ingot grown by cast technique with seed crystal for solar cells, Journal of Applied Physics, 10.1063/1.3700250, 111, 7, 2012.04, [URL], Although crystalline silicon is widely used as substrate material for solar cell, many defects occur during crystal growth. In this study, the generation of crystalline defects in silicon substrates was evaluated. The distributions of small-angle grain boundaries were observed in substrates sliced parallel to the growth direction. Many precipitates consisting of light elemental impurities and small-angle grain boundaries were confirmed to propagate. The precipitates mainly consisted of Si, C, and N atoms. The small-angle grain boundaries were distributed after the precipitation density increased. Then, precipitates appeared at the small-angle grain boundaries. We consider that the origin of the small-angle grain boundaries was lattice mismatch and/or strain caused by the high-density precipitation..
113. Karolin Jiptner, Masayuki Fukuzawa, Yoshiji Miyamura, Hirofumi Harada, Koichi Kakimoto, Takashi Sekiguchi, Evaluation of residual strain in directional solidified mono-Si ingots, Physica Status Solidi (C) Current Topics in Solid State Physics, 10.1002/pssc.201200884, 10, 1, 141-145, 2013.01, [URL], Cast-grown mono-like Si ingots for photovoltaic application are getting increasing attention due to the possibility of obtaining highly efficient solar cells at a low-cost production process. The reduction of crystallographic defects is essential to reach that potential. In this study, the residual strain and dislocation distribution in monolike ingots grown by directional solidification was experimentally determined. It was found that both strain and dislocations are mainly concentrated in the periphery of the ingots.
114. T. Tachibana, T. Sameshima, T. Kojima, K. Arafune, Koichi Kakimoto, Y. Miyamura, H. Harada, T. Sekiguchi, Y. Ohshita, A. Ogura, Evaluation of silicon substrates fabricated by seeding cast technique, 14th International Conference on Defects-Recognition, Imaging and Physics in Semiconductors, DRIP-14
Defects-Recognition, Imaging and Physics in Semiconductors XIV
, 10.4028/www.scientific.net/MSF.725.133, 725, 133-136, 2012, [URL], We evaluated the properties of crystalline defects in silicon substrate, and clarified the origin of small-angle grain boundaries. In order to eliminate the effects of grain boundaries, the ingot was fabricated by unidirectional solidification technique with seed crystal. In single-crystalline region, σ3 twin boundaries and SiC precipitates were observed near the seed crystal. No obvious correlation between twin boundaries and precipitates was observed. These defects decreased once and the precipitations appeared again. The density of precipitates increased through the crystal growth procedure. These precipitates were consisted of Si, C, and N. After the precipitation density increased, the small-angle grain boundaries appeared and some precipitates were observed at the boundaries. We considered the precipitation consisted of light element impurities such as C and N was one of the major origins of the small-angle grain boundary generation..
115. Kenji Shiraishia, Kazuki Sekiguchi, Hiroki Shirakawa, Kenta Chokawa, Masaaki Araidaia, Yoshihiro Kangawa, and Koichi Kakimoto, First Principles and Themodynamical Studies on Matel Organic Vaper Phase Epitaxy of GaN, ECS Transactions, doi: 10.1149/08001.0295ecst, 80, (1), 295--301, 2017.11.
116. Masato Inoue, Hiroyuki Kageshima, Yoshihiro Kangawa, Koichi Kakimoto, First principles approach to C aggregation process during 0th graphene growth on SiC(0001), 31st International Conference on the Physics of Semiconductors, ICPS 2012
Physics of Semiconductors - Proceedings of the 31st International Conference on the Physics of Semiconductors, ICPS 2012
, 10.1063/1.4848319, 1566, 129-130, 2013.01, [URL], The C clustering process during the 0th graphene growth on SiC(0001) was investigated by a first principles approach. It was found that the structure of C clusters is not purely-hexagonal but penta-heptagonal, including pentagons and heptagons. We also revealed that mono-ring clusters, the lowest-energy clusters in vacuum, are no longer the ground-state configuration on SiC(0001). This result suggests a template effect of SiC(0001) for the growth of graphene..
117. K. Sekiguchi, H. Shirakawa, Y. Yamamoto, M. Araidai, Yoshihiro Kangawa, Koichi Kakimoto, K. Shiraishi, First-principles and thermodynamic analysis of trimethylgallium (TMG) decomposition during MOVPE growth of GaN, Journal of Crystal Growth, 10.1016/j.jcrysgro.2016.12.044, 468, 950-953, 2017.06, [URL], We analyzed the decomposition mechanisms of trimethylgallium (TMG) used for the gallium source of GaN fabrication based on first-principles calculations and thermodynamic analysis. We considered two conditions. One condition is under the total pressure of 1 atm and the other one is under metal organic vapor phase epitaxy (MOVPE) growth of GaN. Our calculated results show that H2 is indispensable for TMG decomposition under both conditions. In GaN MOVPE, TMG with H2 spontaneously decomposes into Ga(CH3) and Ga(CH3) decomposes into Ga atom gas when temperature is higher than 440 K. From these calculations, we confirmed that TMG surely becomes Ga atom gas near the GaN substrate surfaces..
118. Masato Inoue, Hiroyuki Kageshima, Yoshihiro Kangawa, Koichi Kakimoto, First-principles calculation of 0th-layer graphene-like growth of C on SiC(0001), Physical Review B - Condensed Matter and Materials Physics, 10.1103/PhysRevB.86.085417, 86, 8, 2012.08, [URL], We use a first-principles approach to analyze the clustering of C atoms during the initial stage of 0th-layer graphene-like growth on SiC(0001). We started the layer with the lowest-energy hexagonal C ring and then let it grow. The growth produced pentagonal rings with a heptagonal ring in a graphene-like (penta-heptagonal) structure. We also studied the chemical potential of C atoms on SiC(0001) and revealed that the C clustering begins at a surface coverage of 0.25-0.33 atom/SiC(0001)-(1×1). Finally, we confirmed that the energetic stabilities of penta-heptagonal clusters on SiC(0001) exceed that of single C rings (7-18 atoms), the lowest-energy structure of free-standing C 7-18 clusters. Hence, the results show that SiC(0001) acts as a template for graphene-like growth..
119. Takahiro Kawamura, Akira Kitamoto, Mamoru Imade, Masashi Yoshimura, Yusuke Mori, Yoshitada Morikawa, Yoshihiro Kangawa, Koichi Kakimoto, First-principles study of the surface phase diagrams of GaN(0001) and (000−1) under oxide vapor phase epitaxy growth conditions, Physica Status Solidi (B): Basic Research, 10.1002/pssb.201600706, 254, 8, 2017.08, [URL], First-principles calculations are used to investigate the stable structures of the GaN(0001) and (000–1) surfaces under oxide vapor phase epitaxy growth conditions. The surface phase diagrams as a function of temperature and Ga pressure are described. It was found that the GaN(0001) surface is covered by OH groups. For the GaN(000–1) surface, the stable surface structure is with H atoms adsorbed on the topmost N atoms or an O atom stably incorporated into the Ga monolayer. We discuss the relationship between the growth conditions and O impurity incorporation. From the results, we suggest that high H2 pressure and high temperature growth conditions are favorable for decreasing O impurity incorporation..
120. Takahiro Kawamura, Akira Kitamoto, Mamoru Imade, Masashi Yoshimura, Yusuke Mori, Yoshitada Morikawa, Yoshihiro Kangawa, Koichi Kakimoto, Toru Akiyama, First-principles study of polar, nonpolar, and semipolar GaN surfaces during oxide vapor phase epitaxy growth, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.7567/JJAP.57.115504, 57, 11, 2018.11, [URL], Stable structures of polar, nonpolar, and semipolar GaN surfaces undergoing oxide vapor phase epitaxy (OVPE) growth were examined with firstprinciples calculations. The relationships between temperature and pressure growth conditions and stable surface structures are described in surface phase diagrams. The results revealed that an O atom was stably incorporated into the N vacancy site in the N-polar and nonpolar surfaces. The desorption energy of the O atom from the GaN surfaces was estimated to be about 7 eV or higher. This indicates that the O atom did not readily desorb from the GaN surfaces under OVPE growth conditions at 1500 K. The desorption energy from the [0001] surface was the highest and that from the [1011] surface was the smallest among the calculated values. There was no significant difference in desorption energy among other surfaces..
121. Koichi Kakimoto and Lijun Liu, Flow Instability of Silicon Melt in Magnetic Fields, FDMP, Vol.2, No.3,167-173., 2006.12.
122. Koichi Kakimoto, Flow instability during crystal growth from the melt, Progress in Crystal Growth and Characterization of Materials, 10.1016/0960-8974(94)00013-J, 30, 2-3, 191-215, 1995.01, [URL], Quality of semiconductor and oxide crystals grown from the melts in Czochralski crystal growth systems is significantly affected by the heat and mass transfer in the melts during growth. This paper reviews the present understanding of this heat and mass transfer, especially melt convection, from the results of flow visualization by using model and real semiconductor melts to the details of numerical calculation needed for quantitative modeling of melt convection. The characteristics of flow instabilities of melt convection with a low Prandtl number are also reviewed by focusing on the baroclinic, the Rayleigh-Benard, and thermoccapillary-Benard instabilities from the viewpoints of temperature and of the effect of rotation during crystal growth. The origin of the flow instabilities is also reviewed on the basis of geostrophic hydrodynamics, and the question whether silicon flow is completely turbulent or has an ordered structure is discussed. Magnetic suppression of melt flow is also reviewed, and some research on new approaches to growth from the melt including molecular dynamics and wavelet transformation will be introduced..
123. Koichi Kakimoto, Masahito Watanabe, Minoru Eguchi, Taketoshi Hibiya, Flow instability of the melt during Czochralski Si crystal growth
dependence on growth conditions; a numerical simulation study, Journal of Crystal Growth, 10.1016/0022-0248(94)90167-8, 139, 3-4, 197-205, 1994.05, [URL], Flow instability of molten Si during Czochralski (CZ) Si crystal growth has been studied utilizing a 3D heat- and mass-transfer model together with global heat- and mass-transfer calculation. It is found that the phase transition from an axisymmetric to a non-axisymmetric mode of the flow occurs depending critically on the growth parameters, such as temperature distribution, crucible as well as crystal rotation rates. In order to prevent the non-axisymmetric instability, low crucible rotation and large temperature difference between the crucible and the crystal are found to be desired. These tendencies are well characterized by the thermal Rossby number and the Taylor number, which represent the relative strengths of Coriolis force to buoyancy force and inertial force. The calculated results are compared and discussed with the experimental observation obtained for the same growth condition..
124. Koichi Kakimoto, Minoru Eguchi, Hisao Watanabe, Taketoshi Hibiya, Flow instability of molten silicon in the Czochralski configuration, Journal of Crystal Growth, 10.1016/0022-0248(90)90884-N, 102, 1-2, 16-20, 1990.04, [URL], The flow instability of molten silicon in the Czochralski configuration has been studied by in-situ observation of melt convection using X-ray radiography and by temperature fluctuation measurement during crystal growth. Flow mode was dependent on an aspect ratio of the melt. For a deep, low aspect ratio melt, with growing crystal which is identical to shouldering process of the growth, the flow was unsteady and non-axisymmetric. For a shallow melt without crystal and crucible rotations, the flow was relatively steady and axisymmetric. However, flow became unsteady and non-axisymmetric for a shallow melt with crystal rotation. Amplitude of directly measured temperature fluctuation in the molten silicon for the case of unsteady and non-axisymmetric flow was larger than that for the relatively steady and axisymmetric flow. The flow instability area, which was also thermally unstable, was found to be larger in the crystal/crucible iso-rotation condition. In contrast Munakata and Tanasawa reported at the International Symposium on Supercomputers for Mechanical Engineering, September 1988, Tokyo that flow instability area was small for the silicone oil with larger Prandtl number..
125. Masahito Watanabe, Minoru Eguchi, Koichi Kakimoto, Haruhiko Ono, Shigeru Kimura, Taketoshi Hibiya, Flow mode transition and its effects on crystal-melt interface shape and oxygen distribution for Czochralski-grown Si single crystals, Journal of Crystal Growth, 10.1016/0022-0248(95)00057-7, 151, 3-4, 285-290, 1995.06, [URL], Flow visualization and crystal growth experiments confirm that the crystal-melt interface shape of the Czochralski-grown silicon crystal is changed by the flow-mode transition of molten silicon caused by the baroclinic instability. They also confirm that the oxygen distribution in the grown crystal is modified by the flow-mode transition. The flow visualization and crystal growth experiments were carried out under the same conditions. The shape of the crystal-melt interface was identified from the growth striation shape in the grown crystal by X-ray topography. The oxygen distribution in the grown crystal was studied using micro Fourier-transform infrared absorption spectroscopy. The crystal-melt interface was changed from a convex to a gull-winged shape by the transition from a non-axisymmetric flow with vortices to an axisymmetric flow. The oxygen distribution along the growth direction in the crystal grown under the axisymmetric flow was more homogeneous than that grown under the non-axisymmetric flow. Experimental results suggest that an inhomogeneous oxygen distribution could result from thermal asymmetry generated by rotating vortices in the non-axisymmetric flow..
126. Koichi Kakimoto, Bing Gao, Fluid Dynamics
Modeling and Analysis, Handbook of Crystal Growth
Bulk Crystal Growth: Second Edition
, 10.1016/B978-0-444-63303-3.00021-3, 2, 845-870, 2014.12, [URL], This chapter summarizes the numerical modeling and analysis of mass transport processes, especially the fluid dynamics of crystal growth systems. It begins with a general description of diffusion in fluids, followed by a discussion of forced and natural convection. The second part relates these phenomena to external forces and flow instability. The chapter closes with a discussion of impurity transfer, including transfer in gaseous phase and at liquid-gas interfaces. Through impurity transfer, we can better understand the effect of the melt surface on convection in crystal growth systems such as Czochralski and directional silicon solidification..
127. X. J. Chen, S. Nakano, L. J. Liu, Koichi Kakimoto, Gedanken experiment on point defects in unidirectional solidified single crystalline silicon with no dislocations, Journal of Crystal Growth, 10.1016/j.jcrysgro.2009.10.035, 312, 2, 192-197, 2010.01, [URL], A gedanken experiment was carried out to investigate point defects formed in unidirectional solidified single crystalline silicon for solar cells, ignoring dislocations in crystals. A transient global model was used to obtain the solution of a thermal field within the entire furnace. Then, based on the global solution of heat transfer, diffusion and recombination of vacancies and interstitials were calculated by the Finite Volume Method (FVM). It was found that vacancies became dominant as the melt was solidified and solidification time was reduced. The ratio between growth rate Vg and temperature gradient in growth direction G was also analyzed. The results revealed that growth rate is the key factor affecting point defects in single crystalline silicon with no dislocations..
128. Koichi Kakimoto, Lijun Liu, Global Analysis of Effects of Magnetic Field Configuration on Melt/Crystal Interface Shape and Melt Flow in a Cz-Si Crystal Growth, Crystal Growth Technology
From Fundamentals and Simulation to Large-scale Production
, 10.1002/9783527623440.ch7, 195-204, 2008.11, [URL].
129. D. Kashiwagi, R. Gejo, Yoshihiro Kangawa, L. Liu, F. Kawamura, Y. Mori, T. Sasaki, Koichi Kakimoto, Global analysis of GaN growth using a solution technique, Journal of Crystal Growth, 10.1016/j.jcrysgro.2007.10.061, 310, 7-9, 1790-1793, 2008.04, [URL], The solution growth technique is one of the key methods for fabricating gallium nitride (GaN) wafers with small dislocation density. Since the growth rate of GaN using the solution technique is small, the key issue of the technique is to enhance the growth rate of the crystal. We studied how nitrogen is transferred from the surface of the flux to the interface between the top of the flux and the crystal in a muffle furnace using a global model that includes radiative, convective and conductive heat and mass transfer, including nitrogen transfer. The average growth rate of GaN increased when the temperature difference between the furnace wall and a crucible wall became large. This phenomenon is based on mixing of the flux due to natural convection..
130. Lijun Liu, Tomonori Kitashima and Koichi Kakimoto, Global analysis of effects of magnetic field configuration on melt-crystal interface shape and melt flow in CZ-Si crystal growth, Journal of Crystal Growth, 10.1016/j.jcrysgro.2004.11.292, 275, 1-2, E2135-E2139, 2005.01.
131. B. Gao, Koichi Kakimoto, Global simulation of coupled carbon and oxygen transport in a Czochralski furnace for silicon crystal growth, Journal of Crystal Growth, 10.1016/j.jcrysgro.2010.07.026, 312, 20, 2972-2976, 2010.10, [URL], For accurate prediction of carbon and oxygen impurities in a single crystal produced by the Czochralski method, global simulation of coupled oxygen and carbon transport in the whole furnace was implemented. Both gas-phase transportation and liquid-phase transportation of oxygen and carbon were considered. With five chemical reactions considered, SiO and CO concentrations in gas and C and O atom concentrations in silicon melt were solved simultaneously. The simulation results show good agreement with experimental data..
132. B. Gao, S. Nakano, and K. Kakimoto, Global Simulation of Coupled Carbon and Oxygen Transport in a Unidirectional Solidification Furnace for Solar Cells, Journal of The Electrochemical Society, 157, H153-H1593, H153-H1593, 2010.02.
133. Ronit R. Prakash, Takashi Sekiguchi, Karolin Jiptner, Yoshiji Miyamura, Jun Chen, Hirofumi Harada, Koichi Kakimoto, Grain growth of cast-multicrystalline silicon grown from small randomly oriented seed crystal, Journal of Crystal Growth, 10.1016/j.jcrysgro.2014.01.067, 401, 717-719, 2014.09, [URL], Multicrystalline silicon was grown from seeds with small grains of random orientation and the growth mechanism was studied with respect to grain size, shape, boundary character and orientation. The average grain size perpendicular to growth direction increased steadily initially, became constant and then increased steadily again. Grain size parallel to growth direction increased rapidly with growth due to grain elongation in the growth direction. Grain shape with respect to growth direction changed from spherical to columnar with growth. Initially non-CSL grain boundary fraction was very high but decreased with growth as the Σ3 grain boundary fraction increased. A simple model was proposed to explain the results..
134. Akira Nagaoka, Ryoji Katsube, Shigeru Nakatsuka, Kenji Yoshino, Tomoyasu Taniyama, Hideto Miyake, Koichi Kakimoto, Michael A. Scarpulla, Yoshitaro Nose, Growth and characterization of Cu2ZnSn(Sx Se1-x)4 single crystal grown by traveling heater method, Journal of Crystal Growth, 10.1016/j.jcrysgro.2015.04.012, 423, 9-15, 2015.08, [URL], Abstract High-quality Cu2ZnSn(SxSe1-x)4 (CZTSxSe1-x) single crystals were grown by the traveling heater method (THM), which is an example of a solution growth process. The CZTSxSe1-x solute-Sn solvent pseudobinary system was investigated and the ranges of growth temperature and quantity of solvent were determined for THM growth. The CZTSxSe1-x single crystals were obtained from a 70-80 mol% CZTSxSe1-x solution at growth temperature 900°C and speed 4-5 mm/day. The structural and compositional analyses of the grown single crystals were carried out by powder X-ray diffraction, Raman spectroscopy and electron probe microanalysis. The grown crystals were kesterite and nearly stoichiometric with slightly Cu-poor and Zn-rich despite the excess Sn used as the solvent. As the sulfur content x increases, the carrier concentration increases slightly but systematically between 2×1017 and 3×1017 cm-3 while the mobility decreases from 35.1 to 10.4 cm2V-1 s-1. These data provide references for the results of characterization on thin film samples as well as giving insight into the defect equilibrium and resulting quantities such as doping and mobility affecting device performance..
135. Akira Nagaoka, Kenji Yoshino, Hiroki Taniguchi, Tomoyasu Taniyama, Koichi Kakimoto, Hideto Miyake, Growth and characterization of Cu2ZnSn(SxSe 1-x)4 alloys grown by the melting method, Journal of Crystal Growth, 10.1016/j.jcrysgro.2013.10.001, 386, 204-207, 2014.01, [URL], I2-II-IV-VI4 quaternary Cu2ZnSn(S xSe1-x)4 (CZTSSe) alloys were successfully grown by the melting growth method. The powder X-ray diffraction (XRD) pattern of the CZTSSe alloys showed preferred orientations of (112), (220) and (312) planes, confirming the Kesterite structure. In Raman spectra, the A1 mode peaks expected for CZTS and CZTSe were observed in all samples, and no secondary phases were observed. The CZTSSe alloys in this study were slightly Cu-poor, Zn-rich and VI-rich, similar to compositions of polycrystalline thin-film materials that have achieved high photovoltaic conversion efficiencies. Single phase and homogeneous CZTSSe alloys were obtained..
136. Akira Nagaoka, Kenji Yoshino, Hiroki Taniguchi, Tomoyasu Taniyama, Koichi Kakimoto, Hideto Miyake, Growth and characterization of Cu2ZnSnS4 single crystals, Physica Status Solidi (A) Applications and Materials Science, 10.1002/pssa.201200815, 210, 7, 1328-1331, 2013.07, [URL], We investigated the growth condition of high-quality Cu 2ZnSnS4 (CZTS) single crystal by traveling heater method (THM) which is one of the solution-based growth methods. We selected Sn as solvent because it is a constituent element of CZTS with low melting point. The solubility of CZTS in Sn solvent was approximately 0.01 mol% at 600 °C and 0.28 mol% at 1000 °C. It is found that CZTS is soluble in Sn solvent, which is similar to CuGaS2 in In solvent. The Sn solutions saturated with CZTS solutes less than 60 mol% were separated with two phases, less than 30 mol% solutions were CZTS and Sn phases and solutions from 30 to 60 mol% were CZTS and SnSx compound phases. It is impossible to grow CZTS single crystal from less than 60 mol% Sn solutions, because secondary phases located at the bottom of the ampoule and interfered with single crystal growth. Optimum growth condition of CZTS was determined based on CZTS-Sn phase diagram, which was growth temperature 900 °C and X = 70 mol% solution. The electrical properties of CZTS single crystal were observed along the growth direction and it can be clearly seen that the electrical properties are homogeneous along the growth direction..
137. A. Kiohita, H. Matsuo, K.Yoshino, T. Ikari, and K. Kakimoto, Growth of AgGaSe2 crystals by hot-press method, Phys. Stat. Sol., (c) 3, No.8, 2903-2906., 2006.10.
138. Koichi Kakimoto, Bing Gao, Xin Liu, Satoshi Nakano, Growth of semiconductor silicon crystals, Progress in Crystal Growth and Characterization of Materials, 10.1016/j.pcrysgrow.2016.04.014, 62, 2, 273-285, 2016.06, [URL], This paper focuses on the recent developments in Czochralski (CZ) crystal growth of silicon for large-scale integrated circuits (LSIs) and multi-crystalline silicon growth using a directional solidification method for solar cells. Growth of silicon crystals by the CZ method currently allows the growth of high-quality crystals that satisfy the device requirements of LSIs or power devices for electric cars. This paper covers how to obtain high-quality crystals with low impurity content and few point defects. It also covers the directional solidification method, which yields crystals with medium conversion efficiency for photovoltaic applications. We discuss the defects and impurities that degrade the efficiency and the steps to overcome these problems..
139. Koichi KAKIMOTO, Heat and Mass Transfer during CZ Crystal Growth: from Atomic Scale to Macro Scale, Abstract of Fourth Asian –Pacific Conference on Aerospace Technology and Science, 2002.01.
140. Koichi Kakimoto, X. J. Chen, L. J. Liu, H. Miyazawa, H. Matsuo, S. Nakano, S. Hisamatsu, Yoshihiro Kangawa, Heat and impurity transfer mechanisms of Czochralski and directional solidification processes, ISTC/CSTIC 2009 (CISTC)
ECS Transactions - ISTC/CSTIC 2009 (CISTC)
, 10.1149/1.3096556, 18, 925-933, 2009.12, [URL], In this paper, results of global computation in a three-dimensional configuration for transverse magnetic field-applied Czochralski method to study distributions of temperature and impurity concentration are presented. The analysis includes a remelting and segregation model at an interface between a crystal and the melt. Deflection of an interface between a crystal and the melt is also taken into account. Time-dependent global analysis of the solidification process of a silicon ingot for photovoltaic is described in this paper. This model includes distributions of dislocation, impurity and point defects for a quasi-single silicon ingot grown by the solidification method. Heat and mass transfers in a square crucible are also discussed..
141. Koichi Kakimoto and Hiroyuki Ozoe, Heat and mass transfer during crystal growth, Computational Materials Science 10, 10.1016/S0927-0256(97)00090-6, 10, 1-4, 127-133, pp.127-133(招待講演), 1998.01.
142. Koichi Kakimoto, Heat and mass transfer in silicon melt under magnetic fields, First International School on Crystal Growth Technology, pp.172-186, 1998.10.
143. Koichi Kakimoto, Heat and mass transfer during CZ crystal growth : From atomic scale to macro scale, Second International School on Crystal Growth Technology, pp.122-144, 2000.08.
144. Koichi Kakimoto, Heat and mass transfer in Czochralski silicon crystal growth under magnetic fields, 20th International Congress of Theoretical and Applied Mechanics, 2000.08.
145. Koichi Kakimoto, Heat and mass transfer in semiconductor melts during single-crystal growth processes, Journal of Applied Physics, 10.1063/1.358882, 77, 5, 1827-1842, 1995, [URL], The quality of large semiconductor crystals grown from melts is significantly affected by the heat and mass transfer in the melts. The current understanding of the phenomena, especially melt convection, is reviewed starting from the results of visualization using model fluids or silicon melt, and continuing to the detailed numerical calculations needed for quantitative modeling of processing with solidification. The characteristics of silicon flows are also reviewed by focusing on the Coriolis force in the rotating melt. Descriptions of flow instabilities are included that show the level of understanding of melt convection with a low Prandtl number. Based on hydrodynamics, the origin of the silicon flow structure is reviewed, and it is discussed whether silicon flow is completely turbulent or has an ordered structure. The phase transition from axisymmetric to nonaxisymmetric flow is discussed using different geometries. Additionally, surface-tension-driven flow is reviewed for Czochralski crystal growth systems..
146. Koichi Kakimoto, Takashige Shinozaki and Yoshio Hashimoto, Heat and oxygen transfer in silicon melt in an electromagnetic Czochralski system with transverse magnetic fields, Int. J. Materials and Product Technology, 22, 1-3, 84-94, 2005.01.
147. Yuren Wang, Koichi Kakimoto, Heating rate dependence of melting of silicon
An in situ x-ray topography study, Journal of Applied Physics, 10.1063/1.1389481, 90, 5, 2247-2251, 2001.09, [URL], In situ observations of the melting processes of dislocation-free silicon crystals were carried out using x-ray topography technique. Heating procedures with various heating rates were used in the experiments. Dot contrasts were observed during the melting process at a high heating rate, while they could not be found at a low heating rate. It was found that the melting process at a high heating rate is spatially inhomogeneous, while that at a low heating rate is homogeneous. It was also found that the oxygen concentration in the sample plays an important role in the formation of dot contrasts during the melting process. The dot contrasts were assumed to originate from the dislocation loops around the oxygen precipitates..
148. Naoki Furuhata, Koichi Kakimoto, Masaji Yoshida, Taibun Kamejima, Heavily Si-doped GaAs grown by metalorganic chemical vapor deposition, Journal of Applied Physics, 10.1063/1.341253, 64, 9, 4692-4695, 1988.12, [URL], Heavily Si-doped GaAs layers were grown by a metalorganic chemical vapor deposition method using disilane (Si2H6) as a silicon dopant source gas. The grown layers were characterized by the van der Pauw, secondary ion mass spectroscopy, and low-temperature Fourier transformation infrared spectroscopy (FTIR) method. The carrier concentration has no growth temperature dependence from 550 to 700 °C temperature range. However, it has temperature dependence below 550 °C and above 700 °C. The carrier concentration of Si-doped GaAs is usually saturated at 6×10 18 cm-3 level. Further, Si doping makes the carrier concentration decrease. By using the low-temperature FTIR method, absorption bands for SiGa, SiAs, Si Ga-SiAs pair, and lower energy bands (374 and 369 cm -1) were observed in heavily Si-doped GaAs. The peak intensity for SiGa is smaller than that for SiAs, and the peak heights at 374 and 369 cm-1 are relatively larger than that for the other peaks. These facts suggest that, in heavily Si-doped GaAs, a part of SiGa formed SiGa related defects, which act as new donor centers..
149. B. Gao, S. Nakano, Koichi Kakimoto, Highly efficient and stable implementation of the Alexander-Haasen model for numerical analysis of dislocation in crystal growth, Journal of Crystal Growth, 10.1016/j.jcrysgro.2013.01.039, 369, 32-37, 2013.02, [URL], To effectively simulate the time evolution of the dislocation density during the crystal growth process under high stress by the Alexander-Haasen model, a fully implicit and fully coupled implementation of the Alexander-Haasen model has been proposed. Numerical tests on low-stress multicrystalline silicon grown in a small furnace and high-stress seed-cast monocrystalline silicon grown in an industrial-scale furnace have been done. Results indicate that the proposed algorithm is highly efficient, strongly stable and applicable to any stress level. This algorithm provides an effective tool to optimize the crystal growth process and reduce dislocation density in industrial-scale furnaces..
150. Tomihisa Tachibana, Takashi Sameshima, Takuto Kojima, Koji Arafune, Koichi Kakimoto, Yoshiji Miyamura, Hirofumi Harada, Takashi Sekiguchi, Yoshio Ohshita, Atsushi Ogura, Impact of light-element impurities on crystalline defect generation in silicon wafer, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.1143/JJAP.51.02BP08, 51, 2 PART 2, 2012.02, [URL], In multi-crystalline silicon grown by unidirectional solidification, there are many origins of crystalline defects. In this study, we investigated the effect of light-element impurities on the generation of crystalline imperfections during crystal growth. In order to control the interfusion of impurities, we regulate the Ar gas flow in the atmosphere on the basis of a computer simulation. The etch pit densities in the sample fabricated without and with Ar gas flow control in the atmosphere were 1.5 × 10 5-7.0 × 10 7 and 5.0 × 10 3-4.0 × 10 5 cm -2, respectively. In the sample fabricated without Ar gas flow control, the precipitates consisting of light-elements were observed in the region where the etch pit density markedly increased. In the region with the highest etch pit density, there were small-angle grain boundaries consisting of dislocations. We believed that the precipitates consisting of light-element impurities were the potential origins of small-angle grain boundaries. The light-element impurities should affect the crystalline defect generation induced during crystal growth, and thereby should be controlled..
151. Yuya Inatomi, Yoshihiro Kangawa, Koichi Kakimoto, Akinori Koukitu, Improved thermodynamic analysis of gas reactions for compound semiconductor growth by vapor-phase epitaxy, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.7567/JJAP.56.038002, 56, 3, 2017.03, [URL], An improved thermodynamic analysis method for vapor-phase epitaxy is proposed. In the conventional method, the mass-balance constraint equations are expressed in terms of variations in partial pressure. Although the conventional method is appropriate for gas-solid reactions occurring near the growth surface, it is not suitable for gas reactions that involve changes in the number of gas molecules. We reconsider the constraint equations in order to predict the effect of gas reactions on semiconductor growth processes. To demonstrate the feasibility of the improved method, the growth process of group-III nitrides by metalorganic vapor-phase epitaxy has been investigated..
152. Koichi Kakimoto and Yuren Wang, In-Situ Observation of Solid-Liquid Interface of Silicon using X –ray Diffraction, The Rigaku-Denki Journal, 2000.01.
153. Y. Miyamura, H. Harada, X. Liu, S. Nakano, S. Nishizawa, Koichi Kakimoto, In-situ measurement of CO gas concentration in a Czochralski furnace of silicon crystals, Journal of Crystal Growth, 10.1016/j.jcrysgro.2018.11.017, 507, 154-156, 2019.02, [URL], Power devices with high-performance require long carrier lifetimes within their silicon crystals. This paper reports the in-situ measurement of carbon monoxide in a Czochralski growth furnace of silicon single crystals. Moreover, this paper reports analytical investigation on contamination to silicon melt as functions of pressure in the furnace, argon gas flow velocity and gap width between the melt and a thermal shield. The experimental results show the carbon contamination to the melt increases when the pressure increases and the flow rate decreases. Increase of the gap width increases the contamination of carbon. We could explain the results qualitatively using a simple transport model..
154. Koichi Kakimoto, Minoru Eguchi, Taketoshi Hibiya, In-situ monitoring of dopant concentration variation in a silicon melt during Czochralski growth, Journal of Crystal Growth, 10.1016/0022-0248(91)90140-Z, 112, 4, 819-823, 1991.01, [URL], In-situ monitoring of dopant concentration variation in a silicon melt during Czochralski growth was performed using an X-ray radiography system. Indium was used as a dopant. The dopant concentration variation in the melt as a function of fraction solidified and of time lapse after growth interruption was also observed experimentally. It is shown that the time constant for dopant concentration variation in the bulk melt just after growth interruption is some tens of minutes. The time constant for variation of convective mode and for temperature oscillation of the melt is also several minutes. Therefore, the time constant for dopant concentration variation is attributed to its diffusion from an accumulated layer just beneath the solid-liquid interface..
155. Koichi Kakimoto, Minoru Eguchi, Hisao Watanabe, Taketoshi Hibiya, In-situ observation of solid-liquid interface shape by X-ray radiography during silicon single crystal growth, Journal of Crystal Growth, 10.1016/0022-0248(88)90118-2, 91, 4, 509-514, 1988.01, [URL], Using X-ray radiography, in-situ observation of solid-liquid interface shape during silicon single crystal growth by a Czochralski method was carried out. Contrast which is attributed to the existence of solid-liquid interface has been obtained. Simulation of transmitted X-ray image by absorption calculation was carried out using absorption coefficients both for molten and for solid silicon, and supports the fact that the solid-liquid interface can be observed. Change of interface shape from convex to concave to the melt during the shouldering process was also in-situ observed..
156. Koichi Kakimoto, Minoru Eguchi, Hisao Watanabe, Taketoshi Hibiya, In-situ observation of impurity diffusion boundary layer in silicon Czochralski growth, Journal of Crystal Growth, 10.1016/S0022-0248(08)80003-6, 99, 1-4, 665-669, 1990.01, [URL], In-situ observation of the impurity diffusion boundary layer during single crystal growth of indium-doped silicon was carried out by X-ray radiography. The difference in the transmitted X-ray image compared with molten silicon just beneath the crystal-melt interface was attributed to the concentration of indium impurities having a larger absorption coefficient. The intensity profile of the transmitted X-ray can be reproduced by a transmittance calculation that considers the meniscus shape and impurity distribution. The impurity distribution profile near the crystal-melt interface was estimated using the Burton-Prim-Slichter (BPS) equation. The observed impurity diffusion boundary layer thickness was about 0.5 mm. It was found that the boundary layer thickness was not constant in the radial direction, which cannot be explained by the BPS theory, since it is based on a one-dimensional calculation..
157. 寒川義裕、柿本浩一、伊藤智徳、纐纈明伯, InGaN混晶半導体における原子配列の理論的検討, 応用物理, 第76巻, 第5号,495-498、, 2007.06.
158. Koichiro Ueno, Edson Gomes Camargo, Takashi Katsumata, Hiromasa Goto, Naohiro Kuze, Yoshihiro Kangawa, Koichi Kakimoto, InSb mid-infrared photon detector for room-temperature operation, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.7567/JJAP.52.092202, 52, 9, 2013.09, [URL], We developed a small InSb mid-infrared (2-7 m wavelength range) photon detector that operates at room temperature. The photodiode was made from (hetero epitaxial) InSb layers that were grown on a semi-insulating GaAs substrate by molecular beam epitaxy. To suppress the effects of the diffusion current of the p-i-n photodiode, we used an AlInSb barrier layer that raises the resistance of the photodiode. We also optimized the device's doping concentration and the infrared incidence window structure. These optimization steps realized high photoelectric current output in a room-temperature environment. We also increased the signal-to-noise ratio of the detector by connecting multiple photodiodes in series. The size of this detector is 1:9 2:7 0:4mm3 and the detectivity is 2:8 108 cm Hz1=2/W at 300 K. This is a practical IR detector that can be used in general signal amplification ICs..
159. Bing Gao, Satoshi Nakano, Koichi Kakimoto, Influence of back-diffusion of iron impurity on lifetime distribution near the seed-crystal interface in seed cast-grown monocrystalline silicon by numerical modeling, Crystal Growth and Design, 10.1021/cg201465t, 12, 1, 522-525, 2012.01, [URL], The distribution of minority carrier lifetime near the seed-crystal interface found in seed cast-grown monocrystalline silicon was clarified in this work. The distribution of lifetime first decreases and then increases from a seed to a crystal. Modeling of the temperature- and time-dependent iron diffusion and segregation during crystal growth showed a concentration distribution of an increase followed by a decrease from a seed to a crystal. The consistency between lifetime and iron distribution near the seed-crystal interface indicates that the back-diffusion of iron impurity from silicon melt into the seed at the duration stage before crystal growth is one of the main reasons for lifetime variation near the seed-crystal interface. Therefore, it is essential to reduce the duration time before crystal growth to obtain good-quality monocrystalline silicon..
160. T. Nagano, Yoshihiro Kangawa, Koichi Kakimoto, Influence of compositional changes of source materials on AlN synthesis using Li-Al-N solvent, Physica Status Solidi (C) Current Topics in Solid State Physics, 10.1002/pssc.200880908, 6, SUPPL. 2, 2009.07, [URL], We carried out AlN synthesis using Li-Al-N solvent. In the present work, Al and Li3N were used as source materials. In this paper, we discuss the variation in phase stability of the products with change in Li-Al-N composition, i.e., Al/Li3N molar ratio. The results suggest that LiAlO2 extra phase was formed in the products under an Al-rich synthesis condition. The oxide formation seems to be caused by oxidation of the nitrogen source. That is, some of the Li3N reacted with H2O in the ambient and to be LiOH, though preparation of the source materials was performed in a glove-box. On the other hand, scanning electron microscopy (SEM) images indicate the possibility of reducing nucleation sites and increasing grain size by optimizing the Al/Li3N molar ratio..
161. Yuriko Matsuo, Yoshihiro Kangawa, Rie Togashi, Koichi Kakimoto, Akinori Koukitu, Influence of hydrogen coverage on Si(111)substrate on the growth of GaN buffer layer, Journal of Crystal Growth, Vol.300, (2007) 66-69., 2007.03.
162. B. Gao, S. Nakano, Koichi Kakimoto, Influence of reaction between silica crucible and graphite susceptor on impurities of multicrystalline silicon in a unidirectional solidification furnace, Journal of Crystal Growth, 10.1016/j.jcrysgro.2010.12.006, 314, 1, 239-245, 2011.01, [URL], The influence of silica crucible reaction with graphite susceptor on carbon and oxygen impurities in multicrystalline silicon was studied by global numerical simulations. Results showed that the crucible reaction has a marked effect on carbon and oxygen impurities in the crystal. When the activity of carbon on the surface of the graphite susceptor increases, both oxygen and carbon impurities in the melt increase rapidly. Therefore, the production of high-purity multicrystalline silicon requires setting a free space between the silica crucible and the graphite susceptor or depositing a layer of SiC film on the surface of susceptor to prevent reaction between them..
163. Takahiro Kawamura, Yoshihiro Kangawa, Koichi Kakimoto, Shigeo Kotake, Yasuyuki Suzuki, Investigation of gan solution growth processes on ga- and n-faces by molecular dynamics simulation, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.1143/JJAP.51.01AF06, 51, 1 PART 2, 2012.01, [URL], We carried out the molecular dynamics simulation of the solution growth of GaN and investigated the growth processes on Ga- and N-faces. An empirical potential function of the Brenner potential was used for the simulations. The simulation cell consisted of GaN substrates with Ga- and N-faces and Ga solution including N atoms. The results showed that the growth surface on the Ga-face laterally developed from a two-dimensional nucleus and became flat. On the other hand, the growth surface on the N-face developed by adhesive growth and became rough..
164. Lijun Liu, Satoshi Nakano, Koichi Kakimoto, Investigation of oxygen distribution in electromagnetic CZ-Si melts with a transverse magnetic field using 3D global modeling, Journal of Crystal Growth, 299 (2007) 48-58., 2006.12.
165. Takahiro Kawamura, Yoshihiro Kangawa and Koichi Kakimoto, Investigation of thermal conductivity of nitride mixed crystals and superlattices by molecular dynamics, Physica Status Solidi (C) Current Topics in Solid State Physics, 10.1002/pssc.200565107, 3, 1695-1699, 2006.07, [URL].
166. Takahiro Kawamura, Yoshihiro Kangawa, Koichi Kakimoto, Investigation of the thermal conductivity of a fullerene peapod by molecular dynamics simulation, Journal of Crystal Growth, 10.1016/j.jcrysgro.2007.11.041, 310, 7-9, 2301-2305, 2008.04, [URL], We investigated the thermal conductivity of a fullerene peapod by molecular dynamics simulation. The thermal conductivity of a peapod was compared with that of a single-walled carbon nanotube (SWNT), and the reason for the difference between them is shown in this paper. Empirical potential functions of Brenner and Lennard-Jones potentials were used for those simulations. Thermal conductivity was calculated by Green-Kubo's equation. The results showed that the values of thermal conductivity of a peapod were larger than those of an SWNT due to the contribution of motion of fullerenes in the peapod..
167. Takahiro Kawamura, Yoshihiro Kangawa, Koichi Kakimoto, Investigation of thermal conductivity of GaN by molecular dynamics, Journal of Crystal Growth, 10.1016/j.jcrysgro.2005.07.018, 284, 1-2, 197-202, 2005.10, [URL], Thermal conductivity of GaN was investigated by molecular dynamics simulation. We used Stillinger-Weber potentials, and Green-Kubo's formula was employed to calculate thermal conductivity. The results showed that the thermal conductivity of GaN at 300 K was in the range of 310<λ<380W/mK, which is higher than the reported experimental values. We also investigated the temperature dependence of thermal conductivity in the temperature range of 300-1200 K..
168. Hideo Ishii, Atsushi Murakawa and Koichi Kakimoto, Isotope-concentration dependence of thermal conductivity of germanium investigated by molecular dynamics, Journal of Applied Physics, 10.1063/1.1711159, 95, 11 I, 6200-6203, 2004.06, [URL].
169. Koichi Kakimoto, Taketoshi Hibiya, Kinetic study by viscosity measurements on direct synthesis of gallium antimonide, Journal of Applied Physics, 10.1063/1.344003, 66, 9, 4181-4183, 1989, [URL], Reaction kinetics for the direct synthesis process of compound GaSb from Ga and Sb metals was studied by observing viscosity changes of the melt during the reaction process. The mole fraction of Ga (cGa) was obtained during synthesis using the equation; log η=cGa(log ηGa +log ηSb)+(1-2cGa)log ηGaSb, where η is the viscosity of the total system, and ηGa, ηSb, and ηGaSb are the viscosities of molten Ga metal, molten Sb metal, and molten GaSb, respectively. The reaction rate was obtained from the variation of the mole fraction of reactant cGa. Assuming a second-order reaction, the activation energy was estimated to be 15.5 kcal/mol..
170. H. Honmou, Koichi Kakimoto, K. Kaede, Low-Loss LD-TO-SINGLE-MODE Fibre Coupling using Twin Graded-Index ROD Lens, Electronics Letters, 10.1049/el:19890035, 25, 1, 49-50, 1989, [URL], A 2 dB low-loss coupling circuit between a DFB laser diode and single-mode fibre has been realised, utilising a newly developed planoconvex, high numerical aperture, low aberration graded-index-rod lens..
171. Koichi Kakimoto, Macroscopic and microscopic mass transfer in silicon Czochralski method, Korean Association of Crystal Growth, Vol.9, No. 4, pp.381-383, 1999.12.
172. Arne Cröll, Taketoshi Hibiya, Suguru Shiratori, Koichi Kakimoto, Lijun Liu, Marangoni Convection in Crystal Growth, Crystal Growth Processes Based on Capillarity
Czochralski, Floating Zone, Shaping and Crucible Techniques
, 10.1002/9781444320237.ch7, 413-464, 2010.04, [URL].
173. Hiroshi Kamimura, Koichi Kakimoto, Materials science education in Japan, Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing, 10.1016/0921-5093(95)09903-4, 199, 1, 15-21, 1995.08, [URL], An example of materials science education in Japan is given. Then key factors in materials science education are discussed. We emphasize that it is important to give students a dream and pleasure in new discovery, and the ambition to open a new frontier field by artificially synthesizing a new material. In this respect the following two subjects are chosen as those appropriate for materials science education, in particular for a graduate course; the dream of a room temperature superconductor and the ambition to see crystal growth visually..
174. Teruaki Katsube, Koichi Kakimoto, Masashi Hara, Measurement of Surface State Distributions in MOS Diodes with a Simple DLTS System, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.1143/JJAP.19.2307, 19, 11, 2307-2308, 1980.01, [URL].
175. Shin NAKAMURA, Taketoshi HIBIYA, Koichi KAKIMO, Nobuyuki IMAISHI, Shin-ichi NISHIZAWA, Akira HIRATA, Kusuhiro MUKAI, Shin-ichi YODA and Tomoji S. MORITA, Measurement of Temperature Fluctuations in Marangoni Convection in a Half-zone Silicon Melt on Board the TR-IA-4 Rocket, J. Jpn. Soc. Microgravity, Appl., Vol.14, No.1, 1997, 60-66, 1997.04.
176. Koichi Kakimoto, Akimasa Tashiro, Hideo Ishii, Takashige Shinozaki, Mechanism of Heat and Oxygen Transfer under Electromagnetic CZ Crystal Growth with Cusp-Shaped Magnetic Fields, Journal of the Electrochemical Society, 10.1149/1.1605423, 150, 10, 2003.10, [URL], The three-dimensional time-dependent flow of the silicon melt in an electromagnetic Czochralski (EMCZ) crystal growth system with cusp-shaped magnetic fields was numerically investigated. Calculations were carried out using five different configurations of the melt and cusp-shaped magnetic fields. The results indicated that oxygen was transferred from a part of a sidewall of the crucible on which a cusp plane of the magnetic fields exists. The results also showed that the oxygen concentration at the solid-liquid interface of silicon increased when the cusp plane of the cusp-shaped magnetic fields shifted from the bottom of the crucible to the surface of the melt..
177. Koichi Kakimoto, Akimasa Tashiro, Takashige Shinozaki, Hideo Ishii, Yoshio Hashimoto, Mechanisms of heat and oxygen transfer in silicon melt in an electromagnetic Czochralski system, Journal Of CRYSTAL GROWTH 243, 10.1016/S0022-0248(02)01473-2, 243, 1, 55-65, pp55-65, 2002.08.
178. Koichi Kakimoto, Melt flow in Czochralski crystal growth system From macro to micro- Crystal Growth Meeting Germany-Japan-Poland, the Institute of Crystal Growth (IKZ) in Berlin, p24, 1999.04.
179. Tomoe Yayama, Yoshihiro Kangawa, Koichi Kakimoto, Akinori Koukitu, Method for theoretical prediction of indium composition in coherently grown InGaN thin films, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.1143/JJAP.48.088004, 48, 8 Part 1, 880041-880042, 2009.12, [URL], InxGa1-xN has attracted considerable interest as a material for multi junction solar cells. In this study, we performed thermodynamic analyses to calculate the relationship between the input In molar ratio and solid composition of a coherently grown InxGa 1-xN thin film that is subjected to planar compressive or tensile stress. The theoretical approach incorporates energy loss of a thin-film system due to lattice constraint from the substrate. The results show that the indium composition x of coherently grown InxGa1-xN is lower than that of stressfree InGaN. This represents the composition pulling effect..
180. Yoshihiro Kangawa, Noriyuki Kuwano, Boris M. Epelbaum, Koichi Kakimoto, Microstructure of bulk AlN grown by a new solution growth method, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.1143/JJAP.50.120202, 50, 12, 2011.12, [URL], We used transmission electron microscopy to analyse the microstructures in a thick AlN layer grown on a self-nucleated, columnar AlN seed crystal. The growth direction of the AlN layer grown by a new solution growth method was [1100]. The threading dislocation (TD) density near the epilayer-seed interface (on the seed crystal) was 109 cm-2. However, owing to dislocation annihilation, the TD density decreased to 108 cm-2 at a thickness of ∼5 μm. These results imply that the new solution growth method can grow high-crystalline-quality bulk AlN under moderate growth conditions (τ ≈ 1200 °C, nitrogen pressure = 1 atm)..
181. H. Maeda, Koichi Kakimoto, M. Kikuchi, J. O. Willis, K. Watanabe, Y. Tanaka, H. Kumakura, Microstructures and superconducting properties of V doped Bi2223 tapes, Applied Superconductivity, 10.1016/S0964-1807(98)00019-2, 5, 1-6, 151-156, 1997.01, [URL], We prepared Ag-sheathed tapes by the powder-in-tube method using V doped Bi2223 powder. We found that V doping into Bi oxide superconductors greatly enhances the Bi2223 phase formation of the tapes without any degradation of the superconducting critical temperature Tc. The doped V is not included in the Bi2223 (or Bi2212) grains, but instead exists as Sr6V2O11 particles with diameters of 0.1 to several micrometers, in which the larger plate-like particles play an important role to promote the formation of the Bi2223 phase. With V doping, the optimum critical current density Jc value is obtained for a short time heat treatment..
182. Lijun Liu, Hiroaki Miyazawa, Satoshi Nakano, Xin Liu, Zaoyang Li, Koichi Kakimoto, Modeling and simulation of Si crystal growth from melt, Physica Status Solidi (C) Current Topics in Solid State Physics, 10.1002/pssc.200880705, 6, 3, 645-652, 2009.12, [URL], A numerical simulator was developed with a global model of heat transfer for any crystal growth taking place at high temperature. Convective, conductive and radiative heat transfers in the furnace are solved together in a conjugated way by a finite volume method. A three-dimensional (3D) global model was especially developed for simulation of heat transfer in any crystal growth with 3D features. The model enables 3D global simulation be conducted with moderate require-ment of computer resources. The application of this numerical simulator to a CZ growth and a directional solidification process for Si crystals, the two major production methods for crystalline Si for solar cells, was introduced. Some typical results were presented, showing the importance and effectiveness of numerical simulation in analyzing and improving these kinds of Si crystal growth processes from melt..
183. B. Gao, Koichi Kakimoto, Modeling grown-in dislocation multiplication on prismatic slip planes for GaN single crystals, Journal of Applied Physics, 10.1063/1.4905946, 117, 3, 2015.01, [URL], To dynamically model the grown-in dislocation multiplication on prismatic slip planes for GaN single crystal growth, the Alexander-Haasen (AH) model, which was originally used to model the plastic deformation of silicon crystals, is extended to GaN single crystals. By fitting the model to the experimental data, we found that it can accurately describe the plastic deformation of GaN caused by prismatic slip. A set of unified parameters for the AH model at different temperatures can be found. This model provides a possible method to minimize grown-in dislocations caused due to prismatic slip by optimizing growing and cooling conditions during GaN single crystal growth..
184. Koichi Kakimoto, Modeling of Fluid Dynamics in the Czochralski Growth of Semiconductor Crystals, Crystal Growth - From Fundamentals to Technology, 10.1016/B978-044451386-1/50009-X, 169-186, 2004.07, [URL], This chapter discusses the problems related to the melt flow during the crystal growth from the melt. It focuses on an analytical approach for determining the effects of the external forces based on the gravitational acceleration and on rotations of a crystal, and does an analysis of the effects of the electric, magnetic, and electromagnetic forces on the melt convection. One of the key points for controlling the vacancy flux in crystals, especially that near a solid-liquid interface, is control of the convection of melt, by which the shape of the solid-liquid interface can be controlled. Crystal growth industries have mainly focused on quantitative prediction of a solid-liquid interface, point defect distribution, oxygen concentration, and dislocation free growth. Since molten silicon, like molten steel or metal, has many free electrons, electromagnetic hydrodynamics can be used to control convection in metallically conducting melt of molten silicon when magnetic or electric fields are applied to the metallically conducting melt. The effects of magnetic fields such as vertical and transverse magnetic fields applied to the Czochralski (CZ) method on convection of the melt are also discussed..
185. L.J.Liu, S. Nakano and K. Kakimoto, Modeling of Segregation of Impurities in Directional Solidification Process for Multi-Crystalline Silicon, 2nd International Workshop on Science and Technology of Crystalline Si Solar Cells , (2007) 52-59., 2007.12.
186. Koichi Kakimoto, Modeling of magnetic fields, AIP Conference Proceedings, 10.1063/1.2751914, 916, 159-175, 2007.09, [URL], This course is aimed at showing how to understand and solve problems of melt flow under magnetic fields during crystal growth from the melt. The course involves the following points. The first part of the course focuses on an analytical approach for determining the effects of external forces based on gravitational acceleration and of rotations of a crystal and a crucible on convection. Analysis of the effects of electric, magnetic and electromagnetic forces on the melt convection will be also introduced..
187. Xin Liu, Lijun Liu, Yuan Wang, Koichi Kakimoto, Modeling of the 3D unsteady melt flow in an industrial-scale Cz-Si crystal growth using LES method, China Semiconductor Technology International Conference 2010, CSTIC 2010
China Semiconductor Technology International Conference 2010, CSTIC 2010
, 10.1149/1.3360747, 27, 1035-1039, 2010.12, [URL], A computational model was presented for the 3D unsteady turbulent melt flow in an industrial-scale Cz-Si growth with Large Eddy Simulation (LES) method in curvilinear grids. The turbulent transport of momentum and heat in the melt was investigated. The turbulent nature of unsteadiness and three-dimensionality of the melt flow was verified. Fluctuation of the thermal field was obviously observed in the melt region close to the melt-crystal interface..
188. Akira Kusaba, Guanchen Li, Michael R. von Spakovsky, Yoshihiro Kangawa, Koichi Kakimoto, Modeling the non-equilibrium process of the chemical adsorption of ammonia on GaN(0001) reconstructed surfaces based on steepest-entropy-ascent quantum thermodynamics, Materials, 10.3390/ma10080948, 10, 8, 2017.08, [URL], Clearly understanding elementary growth processes that depend on surface reconstruction is essential to controlling vapor-phase epitaxy more precisely. In this study, ammonia chemical adsorption on GaN(0001) reconstructed surfaces under metalorganic vapor phase epitaxy (MOVPE) conditions (3Ga-H and Nad-H + Ga-H on a 2 × 2 unit cell) is investigated using steepest-entropy-ascent quantum thermodynamics (SEAQT). SEAQT is a thermodynamic-ensemble based, first-principles framework that can predict the behavior of non-equilibrium processes, even those far from equilibrium where the state evolution is a combination of reversible and irreversible dynamics. SEAQT is an ideal choice to handle this problem on a first-principles basis since the chemical adsorption process starts from a highly non-equilibrium state. A result of the analysis shows that the probability of adsorption on 3Ga-H is significantly higher than that on Nad-H + Ga-H. Additionally, the growth temperature dependence of these adsorption probabilities and the temperature increase due to the heat of reaction is determined. The non-equilibrium thermodynamic modeling applied can lead to better control of the MOVPE process through the selection of preferable reconstructed surfaces. The modeling also demonstrates the efficacy of DFT-SEAQT coupling for determining detailed non-equilibrium process characteristics with a much smaller computational burden than would be entailed with mechanics-based, microscopic-mesoscopic approaches..
189. Masahito Watanabe, Koichi Kakimoto, Minoru Eguchi, Taketoshi Hibiya, Modification of heat and mass transfers and their effect on the crystal-melt interface shape of Si single crystal during Czochralski crystal growth, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 36, 10, 6181-6186, 1997.12, The modification of heat transfer in molten silicon during Czochralski (CZ) crystal growth is discussed by focusing on the transition of the flow mode from axisymmetric to nonaxisymmetric, in order to clarify the mechanism of crystal-melt interface shape deformation. Heat transfer in silicon melt is observed by measuring the difference in temperature near the crucible wall and at the crystal-melt interface with simultaneous observation of molten silicon flow. We confirm that the heat transfer coefficient of silicon melt is reduced when the flow mode is changed from axisymmetric to non-axisymmetric. The crystal-melt interface shape changed as a result of the modified heat transfer, which is due to the flow mode transition from axisymmetric to non-axisymmetric..
190. Takahiro Kawamura, Hiroya Hayashi, Takafumi Miki, Yasuyuki Suzuki, Yoshihiro Kangawa, Koichi Kakimoto, Molecular beam epitaxy growth of GaN under Ga-rich conditions investigated by molecular dynamics simulation, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.7567/JJAP.53.05FL08, 53, 5 SPEC. ISSUE 1, 2014.01, [URL], Molecular beam epitaxial growth of GaN under Ga-rich conditions was simulated using a classical molecular dynamics method. We investigated nitrogen incorporation into the growth surface and the initial growth process using two kinds of simulation models: the Ga adlayer model and Ga droplet model. The simulation of the Ga adlayer model showed that the injected N atom diffused through the Ga adlayer and nucleation occurred in the solid/liquid interface. The simulation of the Ga droplet model showed that the injected N atom diffused on the bare GaN crystal surface and nucleation occurred at the edge of the Ga droplet. In the both simulations, scattering of injected N atoms on the surface of the Ga layer was often observed. Because Ga atoms in the Ga layer were intensively moving compared with that in the GaN crystal, injected N atoms were probably scattered by collisions with the Ga atoms in the Ga layer..
191. Tomonori Kitashima, Koichi Kakimoto and Hiroyuki Ozoe, Molecular dynamics analysis of diffusion of point defects in GaAs, Journal of The Electrochemical Society, 10.1149/1.1543569, 150, 3, G198-G202, 2003.03, [URL].
192. Koichi Kakimoto, T. Umehara, H. Ozoe, Molecular dynamics analysis on diffusion of point defects, Journal of Crystal Growth, 10.1016/S0022-0248(99)00646-6, 210, 1, 54-59, 2000.03, [URL], Molecular dynamics simulation was carried out to estimate diffusion constants and mechanism of point defects such as a single vacancy and a self-interstitial atom under hydrostatic pressure. The Stillinger-Weber potential was used-as a model potential, which is widely accepted for modeling of silicon crystals and melts. We obtained the following results on a self-interstitial atom from the calculation. (1) Diffusion constants of self-interstitial are almost independent of pressure in the range from -50 to +50 kbar. (2) A self-interstitial atom diffuses with the formation of dumbbell structure, which is aligned in [1 1 0] direction. For single vacancy, the following clarified. (1) Diffusion constants of vacancy are also independent of pressure in the range from -40 to +40 kbar. (2) A vacancy diffuses with a switching mechanism to the nearest-neighbor atoms in lattice site..
193. Koichi Kakimoto, T. Umehara, H. Ozoe, Molecular dynamics analysis of point defects in silicon near solid-liquid interface, Applied Surface Science, 10.1016/S0169-4332(00)00121-5, 159, 387-391, 2000.01, [URL], Molecular dynamics simulation was carried out to clarify pressure effects on diffusion constants of point defects such as a vacancy and an interstitial atom under constant pressure by using Stillinger-Weber potential. The calculated results indicate that the pressure effect on diffusion of the point defects is small during single crystal growth of silicon, since stress. which was obtained by a global heat and mass transfer model is not enough to modify migration process of the point defects. Activation energy of a vacancy and an interstitial atom was obtained as a function of external pressure..
194. Koichi Kakimoto, Shin Kikuchi and Hiroyuki Ozoe, Molecular dynamics simulation of oxygen in silicon melt, The Second Symposium on Atomic-scale Surface and Interface Dynamics, pp.85-90, 1998.02.
195. Ryosuke Iguchi, Takahiro Kawamura, Yasuyuki Suzuki, Masato Inoue, Yoshihiro Kangawa, Koichi Kakimoto, Molecular dynamics simulation of graphene growth by surface decomposition of 6H-SiC(0001) and (0001̄), Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.7567/JJAP.53.065601, 53, 6, 2014.01, [URL], Much attention has been paid to graphene growth by the surface decomposition of SiC. A SiC substrate surface contains a Si-terminated (0001) face and a C-terminated (0001̄) face. It was reported that graphene layers on these two faces have different structures and electronic properties. We studied the effects of the SiC substrate surface, i.e., of the Si-face and C-face, and annealing temperature on graphene growth using classical molecular dynamics (MD) simulation. It was found that quality of graphene on the Si-face was better than that on the C-face. In addition, graphene coverage was high at a high annealing temperature..
196. Takahiro Kawamura, Yoshihiro Kangawa, Koichi Kakimoto, Yasuyuki Suzuki, Molecular dynamics simulation of diffusion behavior of N atoms on the growth surface in GaN solution growth, Journal of Crystal Growth, 10.1016/j.jcrysgro.2012.04.022, 351, 1, 32-36, 2012.07, [URL], In this study, we simulated the solution growth of gallium nitride (GaN) and investigated the diffusion behavior of nitrogen (N) atoms on growth surfaces by molecular dynamics simulation. The simulation showed that the Ga-face grew flatter than the N-face. Comparing the diffusion coefficients of a N atom on Ga- and N-faces, the values on the Ga-face were about 3.5 times larger than those on the N-face..
197. Takahiro Kawamura, Yoshihiro Kangawa, Koichi Kakimoto, Molecular dynamics simulation of thermal conductivity of GaN/AlN quantum dot superlattices, Physica Status Solidi (C) Current Topics in Solid State Physics, 10.1002/pssc.200674784, 4, 7, 2289-2292, 2007.12, [URL], We calculated thermal conductivity of GaN/AlN quantum dot superlattices by molecular dynamics simulation. The results of investigation of the effect of quantum dots on thermal conductivity as a function of superlattice period are presented in this paper. An empirical potential function of Stillinger-Weber potential was used for simulations. Thermal conductivity was obtained by Green-Kubo's equation. The results show that the values of thermal conductivity parallel to the wetting layers decreased due to the effect of quantum dots..
198. Koichi Kakimoto, Shin Kikuchi, Hiroyuki Ozoe, Molecular dynamics simulation of oxygen in silicon melt, Journal of Crystal Growth, 10.1016/S0022-0248(98)01115-4, 198-199, PART I, 114-119, 1999.01, [URL], Molecular dynamic simulation of an oxygen atom in silicon crystal and the melt was carried out to obtain the diffusion constants of oxygen in the melt. The simulation using mixed potential in the melt, in which an oxygen atom and 216 silicon atoms were taken into account has been carried out. Vibration frequencies of oxygen and vacancy-oxygen (V-O) pair in the crystal have been calculated. Calculated frequency of oxygen and V-O pair were 1000 and 820 cm-1, respectively, while the experimental results which were obtained from Fourier transform spectra of infrared absorption (FTIR) are 1100 and 830 cm-1, respectively. Oxygen diffusion constant was obtained in an elevated temperature of 1700 K. Calculated diffusion constant of oxygen in the melt was 1 × 10-4 cm2/s..
199. Koichi Kakimoto, Molecular dynamics simulation of mass transfer in molten silicon, Journal of Applied Physics, 10.1063/1.359498, 77, 8, 4122-4124, 1995.12, [URL], The diffusion constant in a silicon melt is calculated using molecular dynamics simulation based on the modified Stillinger-Weber [Phys. Rev. B 31, 5262 (1985)] interatomic potential in the temperature range 1550 K-4 exp(-0.27 eV/kT)cm2/s. Viscosity of the silicon melt, which correlates to the diffusion constant, is also estimated using Eyring's relation reported by S. Glasstone, K. J. Laidler, and H. Eyring [McGraw-Hill, New York (1941)]. The calculated viscosity correlates well with experimental data which were obtained by an oscillating cup method except in the temperature range from 1550 to 1750 K..
200. Yoshihiro Kangawa, Koichi Kakimoto, Tomonori Ito, Akinori Koukitu, Monte Carlo simulation of atomic arrangement in InGaN thin film grown by MOVPE, Journal of Crystal Growth, 10.1016/j.jcrysgro.2008.09.014, 311, 3, 463-465, 2009.01, [URL], It is known that InGaN LED can emit brilliant light though ∼108 cm-2 of threading dislocations exists in the active layer. Recently, the origin of defect-insensitive emission was studied [Chichibu et al., Nature Materials 5 (2006) 810] and elucidated that -In-N- zigzag atomic chains act as effective radiative recombination centers. Relationships between growth conditions and atomic arrangements in InGaN thin films were investigated by Monte Carlo simulation in the present study. Estimated density of -In-N- zigzag atomic chains in the grown films are more than 1020 cm-3 which is large enough compared with the density of non-radiative recombination centers, i.e., <5×1018 cm-3, evaluated by Chichibu et al..
201. Jun Kawano, Yoshihiro Kangawa, Koichi Kakimoto, N substitution in GaAs(001) surface under an atmosphere of hydrogen, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.1143/JJAP.51.10ND17, 51, 10 PART 2, 2012.10, [URL], First-principles calculations of GaAsN surface with low nitrogen (N) content grown by chemical beam epitaxy were performed to theoretically analyze the incorporation process of nitrogen and impurities at the atomic scale. As a result, stable surface structures of GaAsN(001) under hydrogen (H) atmosphere were determined. In these structures, N is suggested to readily substitute into surface sites, especially those that bond with H, compared with in the bulk. This indicates that N is incorporated into a thin film together with H. This may generate H-related defects, which may lead to the degradation of its electric properties. These defects are difficult to minimize by post-annealing processes. Therefore, the amount of H attached to the growth surface should be reduced in order to obtain high-quality crystals. The calculated surface phase diagram suggests that a condition in which the extent of the incorporation of H-related defects can be reduced exists..
202. Lijun Liu, Satoshi Nakano and Koichi Kakimoto, NUMERICAL ANALYSIS OF AN ELECTROMAGNETIC CZ-SI GROWTH PROCESS BY 3D GLOBAL MODELING, Proceedings of HT 2005, 2005 ASME Summer Heat Transfer Conference, 10.1115/HT2005-72496, 229-235, 2005.01.
203. Koichi Kakimoto, Minoru Eguchi, Hisao Watanabe, Taketoshi Hibiya, Natural and forced convection of molten silicon during Czochralski single crystal growth, Journal of Crystal Growth, 10.1016/0022-0248(89)90016-X, 94, 2, 412-420, 1989.02, [URL], Natural and/or forced convection of molten silicon during Czochralski single crystal growth was directly observed using X-ray radiography with solid tracers for various crystal and crucible rotation speeds, and temperature distribution in a crucible holder. Downflow attributed to natural convection in the center of a crucible which had been simulated by numerical calculation was scarcely observed with and without crucible rotation. Numerical simulation of the molten silicon was carried out by a packaged code of "FLUENT"; in the calculation, measured non-axisymmetric temperature distribution in a crucible holder was adopted. Unidirectional flow with and without crucible rotations can be qualitatively explained by the numerical simulation with non-axisymmetric temperature distribution in the crucible holder. The particle path attributed to natural convection near the solid-liquid interface was suppressed downward with increase in crystal rotation speed. The phenomena can be explained by a generation of forced convection beneath the rotating crystal..
204. Dongmei Luo, Wenxue Wang, Yoshihiro Takao, Koichi Kakimoto, New method to determine the exact periodic boundary conditions for macro-microscopic homogenization analysis and its application on the prediction of effective elastic constants of periodic materials, Jixie Qiangdu/Journal of Mechanical Strength, 28, 4, 517-523, 2006.08, A new method is proposed to determine the exact periodic boundary conditions for the macro-microscopic homogenization analysis of materials with periodic micro-structures. A homogeneous integral equation is derived to replace the conventional inhomogeneous integral equation related to the microscopic mechanical behavior in the basic unit cell by introducing a new characteristic function. Based on the new solution method, the computational problem of the characteristic function subject to initial strains and periodic boundary conditions is reduced to a simple displacement boundary value problem without initial strains, which simplifies the computational process. Applications to the predication of effective elastic constants of materials with various two-dimensional and three-dimensional periodic microstructures are presented. The numerical results are compared with empirical results obtained from the Halpin-Tsai equations, Mori-Tanaka method and conventional homogenization calculations, which proves that the present method is valid and efficient for prediction of the effective elastic constants of materials with various periodic microstructures..
205. Wen-Xue Wang, Dongmei Luo, Yoshihiro Takao, Koichi Kakimoto, New solution method for homogenization analysis and its application to the prediction of macroscopic elastic constants of materials with periodic microstructures, Computers and Structures, 2006.06.
206. Yoshihiro Kangawa, Ryutaro Toki, Tomoe Yayama, Boris M. Epelbaum, Koichi Kakimoto, Novel solution growth method of bulk AlN using Al and Li3N solid sources, Applied Physics Express, 10.1143/APEX.4.095501, 4, 9, 2011.09, [URL], In this work, we developed a solution growth method that uses Li-Al-N solution to epitaxially grow AlN on a self-nucleated, columnar AlN seed crystal. The seed crystal was grown by physical vapor transport, and the solution was obtained by annealing a Li3N-Al mixture. The epitaxial AlN grew ∼5 μm in 10 h. Scanning electron microscopy analyses showed that the grown layer had many voids near the epilayer/seed interface, but no evidence of cracks. Using transmission electron microscopy analyses, we found that the growth direction of the AlN was [1100] and the layer had threading dislocation propagating along [1100] with a density of ∼4 × 108 cm -2..
207. Koichi KAKIMOTO, Takao TSUKADA, Nobuyuki IMAISHI, Numerical Analyses of Czochralski Furnace for Single Crystal Growth, Journal of the Heat Society of Japan, Vol.46, No.196,49-57., 2007.07.
208. Lijun LIU and Koichi KAKIMOTO, Numerical Analysis of a TMCZ Silicon Growth Furnace by Using a 3D Global Model, Reports of Research Institute for Applied Mechanics,Kyushu University,, 2004.01.
209. Bing Gao, Satoshi Nakano, and Koichi Kakimoto, Numerical Analysis of Impurity Transport in a Unidirectional Solidification Furnace for Multicrystalline Silicon, 日本結晶成長学会誌, 36, 4, 21-27
, 2010.01.
210. Koichi Kakimoto, Numerical Analysis of Selected Processes in Directional Solidification of Silicon for Photovoltaics, Crystal Growth Technology
Semiconductors and Dielectrics
, 10.1002/9783527632879.ch4, 65-74, 2010.07, [URL].
211. Xin Liu, Hirofumi Harada, Yoshiji Miyamura, Xue feng Han, Satoshi Nakano, Shinichi Nishizawa, Koichi Kakimoto, Numerical analyses and experimental validations on transport and control of carbon in Czochralski silicon crystal growth, Journal of Crystal Growth, 10.1016/j.jcrysgro.2018.07.020, 499, 8-12, 2018.10, [URL], Czochralski silicon (CZ-Si) crystal growth is invariably accompanied by the generation and transport of impurities, such as carbon (C) and oxygen (O), from chemical reactions in the high-temperature range. Reduction of C contamination in the grown crystal is required for the production of a high-quality Si wafer. Therefore, we systematically performed the transient global simulations and in situ measurements of CO concentrations in argon (Ar) gas domain. Parametric studies on the furnace pressure, flow rate of argon gas, and gap width were conducted for the transport of CO and accumulation of C during the melting process of Si feedstock. SiO etching reactions on graphite and SiC coating are the major sources of CO production. The contact reaction between the crucible and susceptor is an additional source of CO and SiO. Furthermore, the control mechanisms of gas flow on the incorporation of the generated CO and the accumulation of C in Si feedstock were clarified by comparison of different parameter settings. According to the mechanisms of C transport, the final C content of the melting process depends on the contamination flux at the gas/melt interface which could be controlled by the Péclet number of the gas flow and diffusion distance of CO..
212. Janusz S. Szmyd, M. Jaszczur, H. Ozoe and K. Kakimoto, Numerical analysis of buoyancy driven convection and radiation from the free surface of the fluid in a vertical cylinder, 3rd European Thermal Sciences Conference, Heidelberg, Germany, 2000.09.
213. Lijun Liu Tomonori Kitashima and Koichi Kakimoto, Numerical analysis of effects of crystal and crucible rotations on melt-crystal interface shape and melt flow in CZ growth by global simulation, A Chinese Journal of Science, Technology & Applications in the Field of Rare Metals, 2003.01.
214. S. Nakano, B. Gao, K. Jiptner, H. Harada, Y. Miyamura, T. Sekiguchi, M. Fukuzawa, Koichi Kakimoto, Numerical analysis of the relation between dislocation density and residual strain in silicon ingots used in solar cells, Journal of Crystal Growth, 10.1016/j.jcrysgro.2016.12.007, 474, 130-134, 2017.09, [URL], We have developed a three dimensional Haasen-Alexander-Sumino model to investigate the distribution of dislocation density and residual strain in Si crystals and compared the calculation results with experimental data performed in mono-like and multicrystalline silicon ingots. The results show that the residual strain in a multicrystal is lower than in a mono-like crystal, whereas the dislocation density in the multicrystal is higher than that in the mono-like crystal. This phenomenon is due to the relation between dislocation density and residual strain caused by the difference of activated slip systems in a mono-like crystal and a multicrystal..
215. S. Nakano, B. Gao, Koichi Kakimoto, Numerical analysis of dislocation density and residual stress in a GaN single crystal during the cooling process, Journal of Crystal Growth, 10.1016/j.jcrysgro.2017.01.034, 468, 839-844, 2017.06, [URL], In this study, we investigate the influence of thermal stress on the dislocation density and residual stress in GaN single crystals by numerical analysis. The results show that the dislocation density increases, but the thermal stress does not decrease, and the residual stress increases throughout the cooling process. The reason for this phenomenon is that the dislocation density is higher at the periphery of the crystal and distribution of dislocation density in the crystal is inhomogeneous. Then, the increase of dislocation does not allow the thermal stress on the entire crystal to relax..
216. Bing Gao, Koichi Kakimoto, Numerical analysis of impurities and dislocations during silicon crystal growth for solar cells, 7th Forum on Science and Technology of Silicon Materials, Silicon Forum 2014
Defects and Impurities in Silicon Materials - An Introduction to Atomic-Level Silicon Engineering
, 10.1007/978-4-431-55800-2_5, 916, 241-272, 2015.01, [URL], Impurities and dislocations in silicon crystals can cause significant deterioration in the conversion efficiency of solar cells. For increasing solar cell efficiency, reduction of impurities and dislocations is necessary. Numerical simulation is a powerful tool for improving the quality of silicon crystal for solar cells. A set of numerical analysis system that includes all processes involved in crystal growth has been developed for studying the carbon and oxygen transport in global furnace, and a three-dimensional Alexander-Haasen model was developed for studying the dislocation multiplication. The simulation helped to reduce carbon and oxygen impurities by designing a simple crucible cover and to decrease the dislocation multiplication and residual stress by using a slow cooling process. Further quality improvements can be achieved using these solvers to optimize furnace structure and operating conditions at a low cost..
217. Makoto Inoue, Satoshi Nakano, Hirofumi Harada, Yoshiji Miyamura, Bing Gao, Yoshihiro Kangawa, Koichi Kakimoto, Numerical analysis of the dislocation density in multicrystalline silicon for solar cells by the vertical bridgman process, International Journal of Photoenergy, 10.1155/2013/706923, 2013, 2013.07, [URL], We studied the effects of cooling process on the generation of dislocations in multicrystalline silicon grown by the vertical Bridgman process. From the temperature field obtained by a global model, the stress relaxation and multiplication of dislocations were calculated using the Haasen-Alexander-Sumino model. It was found that the multiplication of dislocations is higher in fast cooling processes. It was confirmed that residual stress is low at high temperatures because the movement of the dislocations relaxes the thermal strain, while the residual stress increases with decreasing temperature, because of reduced motion of dislocations and formation of a strain field at lower temperatures..
218. F. Inui, B. Gao, S. Nakano, Koichi Kakimoto, Numerical analysis of the velocity of SiC growth by the top seeding method, Journal of Crystal Growth, 10.1016/j.jcrysgro.2012.03.036, 348, 1, 71-74, 2012.06, [URL], Velocity of crystal growth of SiC in a process of solution growth was studied on the basis of a global model of heat and mass transfer in conjunction with a phase diagram of the Si-C system. The growth rate was estimated by flux of carbon to a seed crystal. The results of calculation showed that growth velocity was increased when temperature of a seed crystal was increased. The temperature dependence of growth velocity was mainly determined by the phase diagram of the Si-C system, although the flow pattern was slightly modified by changing temperature distribution in the furnace..
219. S. Nakano, X. J. Chen, B. Gao, Koichi Kakimoto, Numerical analysis of cooling rate dependence on dislocation density in multicrystalline silicon for solar cells, Journal of Crystal Growth, 10.1016/j.jcrysgro.2010.11.009, 318, 1, 280-282, 2011.03, [URL], We investigated the influence of cooling rate on dislocation density in multicrystalline silicon using the unidirectional solidification process for solar cells. The results showed that the maximum value of dislocation density is decreased and that of residual stress is increased in a fast cooling process. These phenomena are attributed to the difference in dwell time at an elevated temperature for multiplication of dislocations..
220. Koichi Kakimoto, Bing Gao, Satoshi Nakano, Numerical analysis of light elements transport in a unidirectional solidification furnace, Physica Status Solidi (C) Current Topics in Solid State Physics, 10.1002/pssc.201000117, 8, 3, 659-661, 2011.03, [URL], Quantitative study of light elements such as carbon and oxygen in multi-crystalline silicon for solar cells is required to grow crystals with high quality. The transport of both carbon and oxygen is one of the critical issues to increase efficiency of solar cells made of silicon materials. Concentrations of carbon and oxygen in a furnace affect each others, therefore it is important to control mass transfer of carbon and oxygen in a furnace. Numerical calculation with a chemical reaction between carbon and oxygen was carried out to study how both light impurities are incorporated into crystals through the melt and gas during solidification process. The effects of flow rate and pressure on the impurities were examined. An increase in the flow rate can reduce both carbon and oxygen impurities in the crystal, though the reduction of carbon is more obvious. An increase in gas pressure can also obviously reduce the oxygen impurity but has only a small effect on the carbon impurity..
221. B. Gao, Koichi Kakimoto, S. Nakano, Numerical analysis of oxygen and carbon transport in a unidirectional solidification furnace, Photovoltaics for the 21 Century 5 - 216th ECS Meeting
Photovoltaics for the 21st Century 5
, 10.1149/1.3300417, 25, 19-24, 2010.12, [URL], A global simulation of coupled oxygen and carbon transport in a unidirectional solidification furnace was carried out for accurate prediction of distributions of carbon and oxygen impurities in multicrystalline silicon material for solar cells. Both the gas flow and silicon melt flow were coupled each other. Five chemical reactions were taken into account during the transportation of the impurities..
222. B. Gao, Koichi Kakimoto, S. Nakano, Numerical analysis of oxygen and carbon transport in a unidirectional solidification furnace, China Semiconductor Technology International Conference 2010, CSTIC 2010
China Semiconductor Technology International Conference 2010, CSTIC 2010
, 10.1149/1.3360744, 27, 1015-1020, 2010.12, [URL], A global simulation of coupled oxygen and carbon transport in a unidirectional solidification furnace was carried out for accurate prediction of distributions of carbon and oxygen impurities in multicrystalline silicon material for solar cells. Both the gas flow and silicon melt flow were coupled each other. Five chemical reactions were taken into account during the transportation of the impurities..
223. Sho Hisamatsu, Hitoshi Matsuo, Satoshi Nakano, Koichi Kakimoto, Numerical analysis of the formation of Si3N4 and Si2N2O during a directional solidification process in multicrystalline silicon for solar cells, Journal of Crystal Growth, 10.1016/j.jcrysgro.2009.02.018, 311, 9, 2615-2620, 2009.04, [URL], We studied the mechanism of formation of Si3N4 and Si2N2O during the solidification process of multicrystalline silicon by numerical analysis with a phase diagram of the Si(l)-N-O system. Concentrations of oxygen and nitrogen were almost the same as reported values of measurements. Si3N4 was formed on the top of the silicon ingot. Si3N4 was also formed at the middle stage of the solidification process at the center of the ingot. It was clarified from the results that Si2N2O was first formed near the melt-crystal interface, since oxygen concentration in the melt decreases and nitrogen concentration in the melt increases with solidification of the molten silicon. Si3N4 was formed after Si2N2O had been formed..
224. Koichi Kakimoto, Hitoshi Matsuo, Syo Hisamatsu, Birava Ganesh, Gao Bing, X. J. Chen, Lijun Liu, Hiroaki Miyazawa, Yoshihiro Kangawa, Numerical analysis of Mc-Si crystal growth, 13th International Autumn Meeting - Gettering and Defect Engineering in Semiconductor Technology, GADEST 2009
Gettering and Defect Engineering in Semiconductor Technology XIII
GADEST 2009
, 10.4028/www.scientific.net/SSP.156-158.193, 156-158, 193-198, 2009.01, [URL], The content and uniformity of impurities and precipitates have an important role in the efficiency of solar cells made of multicrystalline silicon. We developed a transient global model of heat and mass transfer for directional solidification for multicrystalline silicon and a dynamic model of SiC particles and silicon nitride precipitation in molten silicon based phase diagrams. Computations were carried out to clarify the distributions of carbon, nitrogen and oxygen based on segregation and the particle formation in molten silicon during a directional solidification process. It was shown that the content of SiC precipitated in solidified ingots increases as a function of the fraction solidified. It was also clarified from the results that Si2N 2O was first formed near the melt-crystal interface, since oxygen concentration in the melt decreases and nitrogen concentration in the melt increases with solidification of the molten silicon. Si3N4 was formed after Si2N2O had been formed..
225. Hiroaki Miyazawa, Lijun Liu, Koichi Kakimoto, Numerical analysis of influence of crucible shape on interface shape in a unidirectional solidification process, Journal of Crystal Growth, 10.1016/j.jcrysgro.2007.12.056, 310, 6, 1142-1147, 2008.03, [URL], We carried out calculations to investigate the melt-crystal (m-c) interface shape with cylindrical and square crucibles and the influence of crucible shape on m-c interface shape using two-dimensional and three-dimensional global analyses. It was found that maximum deformation of the m-c interface occurs near the corner of the square crucible because outgoing heat flux, which has a significant influence on the m-c interface shape, has three-dimensionality. It was also found that shape and dimensions of the crucible have significant influence on the amount of outgoing heat flux. The results indicate that we should control not only heater power, growth ratio and melt flow but also shape and dimensions of crucibles in order to reduce deformation of the m-c interface..
226. Hiroaki Miyazawa, Lijun Liu, Sho Hisamatsu, Koichi Kakimoto, Numerical analysis of the influence of tilt of crucibles on interface shape and fields of temperature and velocity in the unidirectional solidification process, Journal of Crystal Growth, 10.1016/j.jcrysgro.2007.12.021, 310, 6, 1034-1039, 2008.03, [URL], We carried out calculations to investigate the influence of tilt of crucibles on the melt-crystal interface shape and fields of temperature and velocity of the melt and/or crystal by three-dimensional global and melt-crystal analyses. It was found that flow velocity was larger in the case of a fixed boundary condition of edge of the interface than that in the case of a relaxed condition. Furthermore, deflection of the interface with a fixed boundary condition was smaller than that without the fixed boundary condition. These results indicate that we should use three-dimensional global analysis with a relaxed boundary condition to investigate the influence of tilt of crucibles on the interface shape and flow velocity..
227. Lijun Liu, Satoshi Nakano, Koichi Kakimoto, Numerical analysis of an electromagnetic CZ-SI growth process by 3D global modeling, 2005 ASME Summer Heat Transfer Conference, HT 2005
Proceedings of the ASME Summer Heat Transfer Conference, HT 2005
, 10.1115/HT2005-72496, 3, 229-235, 2005.12, [URL], Three-dimensional (3D) thermal flow of silicon melt in an electromagnetic Czochralski (CZ) system was numerically investigated with a recently developed 3D global model. The electromagnetic CZ system was established with a transverse magnetic field and an injected electric current applied on the melt surface. Different azimuthal and radial positions of the electrode on the melt surface were taken into account to investigate their influences on the heat and mass transfer in the melt, as well as on the melt-crystal interface. The influence of the electric current direction on the melt flow pattern and temperature distribution was also demonstrated. The results showed that the position of the electrode on the melt surface and the direction of the applied electric current play an important role in controlling the heat and mass transfer in the silicon melt..
228. Tomonori Kitashima, Lijun Liu, Kenji Kitamura, Koichi Kakimoto, Numerical analysis of continuous charge of lithium niobate in a double-crucible Czochralski system using the accelerated crucible rotation technique, Journal of Crystal Growth, 10.1016/j.jcrysgro.2004.02.036, 266, 1-3, 109-116, 2004.05, [URL], The transport mechanism of supplied raw material in a double-crucible Czochralski system using the accelerated crucible rotation technique (ACRT) was investigated by three-dimensional and time-dependent numerical simulation. The calculation clarified that use of the ACRT resulted in enhancement of the mixing effect of the supplied raw material. It is, therefore, possible to maintain the composition of the melt in an inner crucible during crystal growth by using the ACRT. The effect of the continuous charge of the raw material on melt temperature was also investigated. Our results showed that the effect of feeding lithium niobate granules on melt temperature was small, since the feeding rate of the granules is small. Therefore, solidification of the melt surface due to the heat of fusion in this system is not likely..
229. Lijun Liu, Tomonori Kitashima, Koichi Kakimoto, Numerical analysis of effects of crystal and crucible rotations on melt-crystal interface shape and melt flow in CZ growth by global simulation, Rare Metals, 22, SUPPL., 12-19, 2003.12, The melt-crystal interface shape and melt flow in the crucible play an important role in control of the crystal quality in Czochralski (CZ) growth. A set of numerical computations was conducted to understand the effects of crystal and crucible rotations on the melt-crystal interface shape and melt flow in a small silicon CZ furnace. The crystal rotation rates ranged from 0 to 30 r/min and the crucible rotation rates from 0 to -10 r/min. A global simulation was employed to obtain a precise knowledge of the heat transfer taking place in the entire furnace. An accurate calculation of radiation exchange between different surfaces in the furnace was carried out with the assumption of diffuse surfaces and with the use of a viewed and hidden part algorithm. A finite control volume method, together with a multi-block technique, was applied to calculate the thermal field in solid domains and flow field of melt in the crucible. The shape of the melt-crystal interface and the heater power of the furnace are variables of the problem and were achieved by iterative procedures. The computations revealed that the crystal and crucible rotations affect the melt flow and melt-crystal interface shape..
230. Masato Akamatsu, Koichi Kakimoto and Hiroyuki Ozoe, Numerical calculation of natural and mixed convection in a Czochralski crucible under transverse magnetic fields Heat Transfer 1998, Proceedings of 11th IHTC, 239-244, Vol.3, pp.239-244, 1998.08.
231. Masato Akamatsu, Koichi Kakimoto and Hiroyuki Ozoe, Numerical computation for the secondary convection in a Czochralski
crystal growing system with a rotating crucible and astatic crystal rod, Journal of Materials Processing & Manufacturing Science, 5, 4, 329-348, Vol.5, No.4, pp.329-348, 1998.04.
232. Xin Liu, Bing Gao, Koichi Kakimoto, Numerical investigation of carbon contamination during the melting process of Czochralski silicon crystal growth, Journal of Crystal Growth, 10.1016/j.jcrysgro.2014.07.040, 417, 58-64, 2015.05, [URL], Abstract Czochralski (CZ) growth of single silicon (Si) crystals is invariably accompanied by transport of impurities such as carbon (C), oxygen (O), and related compounds produced by reactions at high temperature. To study the generation and accumulation of C during the melting process, a transient global model was developed that included coupled O and C transport. Transport phenomena of C, O, and related compounds were predicted by considering five chemical reactions in the furnace. The dynamic behavior of impurities was revealed during the melting process of the Si feedstock. It was found that C contamination is activated once the melting front contacts argon gas. For accurate control of C contamination in CZ-Si crystals, the accumulation of C during the melting stage should be considered. Parameter studies of furnace pressure and gas flow rate were conducted on the accumulation of C during the melting stage. At the gas/melt interface, pressure and flow rate affected the C flux in different ways. The results suggest that increase in gas flow rate could reduce C contamination much more effectively than decrease in pressure..
233. Xin Liu, Bing Gao, Satoshi Nakano, Koichi Kakimoto, Numerical investigation of carbon and silicon carbide contamination during the melting process of the Czochralski silicon crystal growth, Crystal Research and Technology, 10.1002/crat.201500014, 50, 6, 458-463, 2015.01, [URL], Carbon contamination in single crystalline silicon is detrimental to the minority carrier lifetime, one of the critical parameters for electronic wafers. In order to study the generation and accumulation of carbon contamination, transient global modeling of heat and mass transport was performed for the melting process of the Czochralski silicon crystal growth. Carbon contamination, caused by the presence of carbon monoxide in argon gas and silicon carbide in the silicon feedstock, was predicted by the fully coupled chemical model; the model included six reactions taking place in the chamber. A simplified model for silicon carbide generation by the reaction between carbon monoxide and solid silicon was proposed using the closest packing assumption for the blocky silicon feedstock. The accumulation of carbon in the melted silicon feedstock during the melting and stabilization stages was predicted. Owing to this initial carbon content in the melt, controlling carbon contamination before the growth stage becomes crucial for reducing the carbon incorporation in a growing crystal..
234. B. Gao, Koichi Kakimoto, Numerical investigation of the influence of cooling flux on the generation of dislocations in cylindrical mono-like silicon growth, Journal of Crystal Growth, 10.1016/j.jcrysgro.2013.09.002, 384, 13-20, 2013.10, [URL], To effectively reduce dislocations during seeded growth of cylindrical monocrystalline-like silicon by controlling the cooling flux, the relationship between the generation of dislocations and cooling flux has been numerically studied. The results show that the generation of dislocations is determined by the cooling flux difference, not by the cooling flux inside the crystal. Good control of the input and output cooling fluxes during practical crystal growth is essential to reduce the generation of dislocations. Further analysis shows that the cooling flux difference in the radial or axial direction is linearly related to the square root of the maximum dislocation density. In other words, a linear decrease of the cooling flux difference in the radial or axial direction results in a quadratic decrease of the maximum dislocation density. Therefore, the most effective method to reduce dislocations during the cooling process is to decrease the cooling flux difference between the input and output fluxes, i.e., to decrease the energy accumulation or dissipation rate inside the whole crystal..
235. Hiroaki Miyazawa, Lijun Liu, Koichi Kakimoto, Numerical investigation of the influence of material property of a crucible on interface shape in a unidirectional solidification process, Crystal Growth and Design, 10.1021/cg800435d, 9, 1, 267-272, 2009.01, [URL], We carried out calculations to investigate the influence of thermal conductivity of the wall of a crucible on melt-crystal interface shape using three-dimensional global analyses. It was found that thermal conductivity of the wall of a crucible has significant influence on the melt-crystal interface shape due to modification of the amount of outgoing heat flux through the wall of a crucible. The results indicate that we should control not only heater power, growth velocity, and melt flow but also thermophysical properties of the wall of a crucible in order to reduce deformation of the melt-crystal interface..
236. Koichi Kakimoto, L. Liu, H. Miyazawa, S. Nakano, D. Kashiwagi, X. J. Chen, Yoshihiro Kangawa, Numerical investigation of crystal growth process of bulk Si and nitrides - A review, Crystal Research and Technology, 10.1002/crat.200711004, 42, 12, 1185-1189, 2007.12, [URL], Heat and mass transfer during crystal growth of bulk Si and nitrides by using numerical analysis was studied. A three-dimensional analysis was carried out to investigate temperature distribution and solid-liquid interface shape of silicon for large-scale integrated circuits and photovoltaic silicon. The analysis enables prediction of the solid-liquid interface shape of silicon crystals. The result shows that the interface shape became bevel like structure in the case without crystal rotation. We also carried out analysis of nitrogen transfer in gallium melt during crystal growth of gallium nitride using liquid-phase epitaxy. The result shows that the growth rate at the center was smaller than that at the center..
237. X. J. Chen, L. J. Liu, H. Tezuka, Y. Usuki, Koichi Kakimoto, Numerical investigation of induction heating and heat transfer in a SiC growth system, Crystal Research and Technology, 10.1002/crat.200710970, 42, 10, 971-975, 2007.10, [URL], A global simulation model is applied for a silicon carbide growth system heated by induction coils. A finite-volume method (FVM) and a global model are applied to solve the equations for electromagnetic field, conductive and radiative heat transfer. The growth rate is predicted by Hertz-Knudsen equation and onedimensional mass transfer equation. Further, simulations for five different coil positions are carried out to investigate the effects of coil position on temperature distribution in the furnace. The numerical results reveal that the variation of temperature in the radial direction along the substrate surface and the temperature difference between the powder and substrate are greatly affected by the coil position. The predicted growth rate along the substrate surface for five coil positions is also studied. Finally, a reasonable range of coil positions maintaining a balance between large-diameter crystal, high growth rate, temperature limitation of material and lower electrical power consumption is obtained..
238. Xuejiang Chen, Shinichi Nishizawa, Koichi Kakimoto, Numerical simulation of a new SiC growth system by the dual-directional sublimation method, Journal of Crystal Growth, 10.1016/j.jcrysgro.2010.02.027, 312, 10, 1697-1702, 2010.05, [URL], A new SiC growth system using the dual-directional sublimation method was investigated in this study. Induction heating and thermal conditions were computed and analyzed by using a global simulation model, and then the values of growth rate and shear stress in a growing crystal were calculated and compared with those in a conventional system. The results showed that the growth rate of SiC single crystals can be increased by twofold by using the dual-directional sublimation method with little increase in electrical power consumption and that thermal stresses can be reduced due to no constraint of the crucible lid and low temperature gradient in crystals..
239. Koichi Kakimoto, Pierre Nicodème, Michael Lecomte, François Dupret, Marcel J. Crochet, Numerical simulation of molten silicon flow; comparison with experiment, Journal of Crystal Growth, 10.1016/0022-0248(91)90421-Z, 114, 4, 715-725, 1991.12, [URL], Numerical simulation containing fluid flow, heat conduction and heat exchange by radiation has been performed using the geometry of a real Czochralski furnace for silicon single crystal growth. The flow velocity fields of molten silicon are obtained from extrapolation of the stream function, which has been newly developed using the velocity boundary layer theory. The calculated flow velocity and particle path are semi-quantitatively identical to the results obtained from X-ray radiography experiment. The calculated value of the characteristic velocity is about 10-2 m/s. The same order of flow velocity which is obtained from the experiment has been already reported. It has also become clear from a comparison of flow velocities between experimental and calculated results that the order of the volume expansion coefficient of the molten silicon (β) is 10-4 K-1. The flow was almost axisymmetric and steady for a specific case with low crystal and crucible rotation rates and with a shallow melt. We also found that a flow with larger azimuthal velocity component exists just beneath a crystal, while that with opposite flow direction exists near the crucible wall..
240. Xiaobo Wu, Koichi Kakimoto, Hiroyuki Ozoe and Zengyue Guo, Numerical study of natural convection in Czochralski crystallization, The Chemical Engineering Journal, 10.1016/S1385-8947(98)00114-4, 71, 3, 183-189, Vol.71, pp.183-189, 1998.12.
241. Y. Kangawa, K. Kakimoto, T. Ito, and A. Koukitu, Numerical study of the relationship between growth condition and atomic arrangement of InGaN, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, (b)244, No.6, (2007) 1784-1788. , 2007.04.
242. Lijun Liu, Koichi Kakimoto, Numerical study of the effect of magnetic fields on melt-crystal interface-deflection in Czochralski crystal growth, 2003 ASME Summer Heat Transfer Conference (HT2003)
Proceedings of the 2003 ASME Summer Heat Transfer Conference, Volume 3
, 2003, 343-351, 2003.12, In order to control the impurity distribution and remove defects in a crystal grown in Czochralski growth for high quality crystals of silicon, it is necessary to study and control the melt-crystal interface shape, which plays an important role in control of the crystal quality. The melt-crystal interface interacts with and is determined by the convective thermal flow of the melt in the crucible. Application of magnetic field in the Czochralski system is an effective tool to control the convective thermal flow in the crucible. Therefore, the shape of the melt-crystal interface can be modified accordingly. Numerical study is performed in this paper to understand the effect of magnetic field on the interface deflection in Czochralski system. Comparisons have been carried out by computations for four arrangements of the magnetic field: without magnetic field, a vertical magnetic field and two types of cusp-shaped magnetic field. The velocity, pressure, thermal and electromagnetic fields are solved with adaptation of the mesh to the iteratively modified interface shape. The multi-block technique is applied to discretize the melt field in the crucible and the solid field of silicon crystal. The unknown shape of the melt-crystal interface is achieved by an iterative procedure. The computation results show that the magnetic fields have obvious effects on both the pattern and strength of the convective flow and the interface shape. Applying magnetic field in the Czochralski system, therefore, is an effective tool to control the quality of bulk crystal in Czochralski growth process..
243. Koichi Kakimoto, Lijun Liu, Numerical study of the effects of cusp-shaped magnetic fields and thermal conductivity on the melt-crystal interface in CZ crystal growth, Crystal Research and Technology, 38, 7-8, 716-725, 2003.08, A numerical study was carried out to determine the effects of magnetic fields and thermal conductivity of a crystal on the melt flow in a crystal growth system. Comparisons of computations for the case of no magnetic field and for two types of cusp-shaped magnetic fields were made. The effect of thermal conductivity of a crystal on the shape of a melt-crystal interface was also investigated. The computation results showed that the magnetic fields have clear effects on both the pattern and strength of flow of the melt and the interface shape. Application of a magnetic field to the Czochralski system is therefore an effective tool for controlling the quality of bulk crystal during Czochralski growth process. The results also showed that the shape of the interface could be modified by changing thermal conductivity of silicon..
244. Terutaka GOTO, Hiroshi YAMAD- KANETA, Yasuhiro SAITO, Yuichi NEMOTO, Koji SATO, Koichi KAKIMOTO and Shintaro NAKAMURA, Observation of Low-Temperature Elastic Softening due to Vacancy in Crystalline Silicon, Journal of the Physical Society of Japan, Vol.75, No.4, (2006) 044602., 2006.04.
245. Terutaka Goto, Hiroshi Yamada-Kaneta, Yasuhiro Saito, Yuichi Nemoto, Koji Sato, Koichi Kakimoto, Shintaro Nakamura, Observation of vacancy in high purity silicon crystal using low-temperature ultrasonic measurements, ECS Transactions, 10.1149/1.2355772, 3, 4, 375-385, 2006.12, [URL], We have succeeded in direct observation of isolated vacancies in high purity silicon crystals grown by a floating zone (FZ) method using low-temperature ultrasonic measurements. The softening of elastic constants below 20 K down to 20 mK is observed in nondoped FZ silicon and B-doped FZ silicon. This softening is caused by an interaction of electric quadrupoles of triply degenerate vacancy orbital to elastic strains of ultrasonic waves. The lowtemperature elastic softening measured by ultrasonic methods verifies existence of the isolated vacancies in Pv-region distributed in pure crystal of a Czockralski ingot. The ultrasonic measurement of the low-temperature softening is a faithful probe for vacancy evaluation in high purity silicon crystals in commercial base. copyright The Electrochemical Society..
246. Mitsuhiro Matsumoto, Hu Huang, Hirofumi Harada, Koichi Kakimoto, Jiwang Yan, On the phase transformation of single-crystal 4H-SiC during nanoindentation, Journal Physics D: Applied Physics, 10.1088/1361-6463/aa7489, 50, 26, 2017.06, [URL], Microstructural changes of single-crystal 4H silicon carbide (SiC) induced by nanoindentation under various conditions were investigated. It was found that nanoindentation at different crystal orientations induced different Raman spectroscopic characteristics. Cross-sectional observation by transmission electron microscopy indicated that a very deep subsurface damage region was formed where dislocations occurring along the basal planes, crystal grains rotation and micro-cracks were observed. The microstructures of the damage regions were strongly affected by the nanoindentation conditions. Coupled analysis of lattice fringes and Raman spectra indicated that a phase transformation from 4H-SiC to 3C-SiC occurred during nanoindentation, which has never been reported before. Furthermore, the 4H to 3C phase transformation strongly depended on the indenter orientation with respect to the SiC crystal. These findings are meaningful for low-damage precision machining of SiC substrates..
247. Masato Akamatsu, Hiroyuki Ozoe, Koichi Kakimoto and Tsuguo Fukuda, One-sided natural and mixed convection computed for liquid metal in a Czochralski configuration, 5th ASME/JSME Joint Thermal Eng. Conf, 1999.03.
248. Hitoshi Matsuo, Takahiro Tokuda, Kenji Yoshino, Aya Kinoshita, Tetsuo Ikari, Koichi Kakimoto, Satoru Seto, Optical charaterization of Ag/Ga composition ratio in AgGaSe2 thin film, Physica Status Solidi (C) Current Topics in Solid State Physics, 10.1002/pssc.200881138, 6, 5, 1070-1073, 2009, [URL], AgGaSe2 thin films, changing the Ag/Ga ratio from 0.4 to 1.5, on glass substrates were successfully grown by vacuum evaporation method. Fundamental absorption bandedges were clearly observed except for Ag/Ga ratios of 0.4 and 1.5 in the optical transmittance spectra at RT. The optical bandgap in-creased with increasing Ag/Ga ratio. This was due to the Bernstein-Moss shifts. Photoluminescence spectrum was strongly observed in the stoichiometric sample in comparison to Ag- and Ga-rich samples. This means that nonradiative re-combination transition was a few in the stoichiometric sample because there were few defects in the samples Two distinct peaks at 1.77 and 1.70 eV were clearly observed in the stoichiometric sample. They were due to bound exciton emis-sion and donor-acceptor pair (DAP) emission, respectively. The DAP emission is due to recombination between Se- and Ga vacancies..
249. B. Gao, Koichi Kakimoto, Optimization of power control in the reduction of basal plane dislocations during PVT growth of 4H-SiC single crystals, Journal of Crystal Growth, 10.1016/j.jcrysgro.2014.02.005, 392, 92-97, 2014.04, [URL], The influence of power control on the multiplication of basal plane dislocations (BPDs) during PVT growth of 4H-SiC single crystals was studied by numerical modeling. Three sets of different power histories during growth were tested: continuously increasing power, continuously decreasing power, and constant power. The results show that optimization of the power history control is crucial for the reduction of basal plane dislocations during growth. If only low BPD density is concerned, then constant low power is the best choice. However, if both low BPD density and high growth rate are desirable, then concave continuously increasing power is the best choice..
250. X. J. Chen, L. J. Liu, H. Tezuka, Y. Usuki, Koichi Kakimoto, Optimization of the design of a crucible for a SiC sublimation growth system using a global model, Journal of Crystal Growth, 10.1016/j.jcrysgro.2007.11.016, 310, 7-9, 1810-1814, 2008.04, [URL], Induction heating, temperature field and growth rate for a sublimation growth system of silicon carbide were calculated by using a global simulation model. The effects of shape of the crucible on temperature distribution and growth rate were investigated. It was found that thickness of the substrate holder, distance between the powder and substrate, and angle between the crucible wall and powder free surface are important for growth rate and crystal quality. Finally, a curved powder free surface was also studied. The results indicate that the use of a curved powder free surface is also an effective method for obtaining a higher growth rate..
251. Koichi Kakimoto, Masahito Watanabe, Minoru Eguchi, Taketoshi Hibiya, Ordered structure in non-axisymmetric flow of silicon melt convection, Journal of Crystal Growth, 10.1016/0022-0248(93)90048-2, 126, 2-3, 435-440, 1993.01, [URL], This paper describes the three-dimensional non-axisymmetric flow of a silicon melt in a silicon Czochralski system. A stable vortex with almost the same angular velocity as the crucible is observed by in-situ detection of silicon melt convection using double X-ray radiography. To determine the flow structure in detail, three-dimensional numerical simulation is also carried out for the same geometry; this gives both the three-dimensional temperature and the velocity fields. The simulation predicts a stable vortex rotating with the crucible. The temperature field is also modulated in the azimuthal direction due to the stable vortex. The results of the experiments and numerical simulation show that the non-axisymmetric flow is due to a baroclinic instability..
252. Karolin Jiptner, Yoshiji Miyamura, Bing Gao, Hirofumi Harada, Koichi Kakimoto, Takashi Sekiguchi, Orientation dependency of dislocation generation in Si growth process, 16th International Conference on Gettering and Defect Engineering in Semiconductor Technology, GADEST 2015
Gettering and Defect Engineering in Semiconductor Technology XVI
, 10.4028/www.scientific.net/SSP.242.15, 15-20, 2016.01, [URL], In an attempt to understand how and where dislocations are introduced into Si ingots bytemperature gradients, bulk dislocation-free FZ crystals are exposed to temperature gradients similar tothose in Bridgman Si crystal growth. This heat treatment introduces dislocations, which were analyzedusing X-ray topography (XRT) and Scanning InfraRedPolariscopy (SIRP). Hereby, the orientationdependency is taken into account and ingots in (001) and (111) growth orientation are evaluated inthis work. It can be found that the dislocation generation takes place at similar regions of the crystaland is independent of orientation, however, their propagation and multiplication differs. This leads toan overall different shape of the dislocation network. Especially intriguing are the long slip lines inthe (111)-crystal, which cannot be found in the (001)-crystal. This suggests a different magnitude ofslip propagation depending on the sample orientation. This effect should be explained by a differentactivation of slip systems and is discussed in the paper..
253. Koichi Kakimoto and Hiroyuki Ozoe, Oxygen distribution at a solid-liquid interface of silicon under transverse magnetic fields, J. of Crystal Growth, 10.1016/S0022-0248(00)00329-8, 212, 3-4, 429-437, Vol. 212, Nos. 3/4, pp.429-437, 2000.06.
254. Koichi Kakimoto, Oxygen distribution in silicon melt under inhomogeneous transverse magnetic fields, Third International Workshop on Modeling in Crystal Growth, 10.1016/S0022-0248(01)01315-X, 230, 1-2, 100-107, pp.181-200, 2000.11.
255. Koichi Kakimoto, H. Ozoe, Oxygen distribution at a solid-liquid interface of silicon under transverse magnetic fields, Journal of Crystal Growth, 10.1016/S0022-0248(00)00329-8, 212, 3, 429-437, 2000.01, [URL], This paper aims to report the effect of transverse magnetic fields on melt convection and oxygen transfers in silicon melt during single-crystal growth. Three-dimensional and time-dependent calculation was carried out to clarify distributions of velocity, temperature and oxygen in the melt. Asymmetric temperature and oxygen distributions were obtained from the calculation, which were due to unidirectional magnetic fields. Oxygen distribution in the melt was also discussed to clarify how surface-tension-driven flow affect the oxygen distribution at an interface between crystals and melt..
256. K. KAKIMOTO, Oxygen distributions in silicon melt under inhomogeneous transverse-magnetic fields, Journal of Crystal Growth , 10.1016/S0022-0248(01)01315-X, 230, 1-2, 100-107, pp100-107, 2001.08, [URL].
257. Koichi Kakimoto, Kyung Woo Yi, Minoru Eguchi, Oxygen transfer during single silicon crystal growth in Czochralski system with vertical magnetic fields, Journal of Crystal Growth, 10.1016/0022-0248(95)00976-0, 163, 3, 238-242, 1996.01, [URL], Oxygen transfer in silicon melts during crystal growth under vertical magnetic fields is investigated numerically and experimentally. A three-dimensional numerical simulation, including melt convection and oxygen transport, is carried out to understand how oxygen transfers in the melt under magnetic fields. Oxygen concentrations in single silicon crystals grown from the melt under these magnetic fields are experimentally measured by using an infrared absorption technique. The results obtained are compared to results from a numerical simulation. An anomalous increase is observed in the oxygen concentration of the grown crystals under a magnetic field of about 0.03 T. The cause of this anomaly is identified as Benard instability, since the temperature at the bottom of the crucible is higher than that at interface. When the temperature at the bottom is decreased, the Benard cell can be removed, and a monotonic decrease in the oxygen concentration in the single silicon crystals can be observed..
258. Kyung Woo Yi, Koichi Kakimoto, Minoru Eguchi, Hiroshi Noguchi, Oxygen transport mechanism in Si melt during single crystal growth in the Czochralski system, Journal of Crystal Growth, 10.1016/0022-0248(96)00212-6, 165, 4, 358-361, 1996.08, [URL], Silicon single crystals were grown in crucibles with and without a carbon sheet at the bottom to investigate how oxygen dissociates from the crucible and transfers to the crystals. Oxygen concentration in the crystals grown in the sheet-attached crucible was lower than that of crystals grown in the sheetless crucible when crucible rotation rate was high. A three-dimensional numerical simulation clarified that with a high crucible rotation rate, about 20% of the oxygen in the grown crystals was transferred by convection in the melt from the bottom of the crucible. For a low crucible rotation rate, a melt with a small oxygen concentration was directly transferred from the gas-melt interface to the crystal-melt interface; therefore, oxygen concentration in crystals grown at a low crucible rotation rate was lower than that for crystals grown at a high rotation rate..
259. Koichi Kakimoto, Katsuto Tanahashi, Hiroshi Yamda- Kaneta, and Tohru Nagasawa, Oxygen-isotope-doped silicon crystals grown by a floating zone method, Journal of Crystal Growth, Koichi Kakimoto, Katsuto Tanahashi, Hisoshi Yamda- Kaneta and Tohru Nagasawa, 2007.03.
260. Lijun Liu and Koichi Kakimoto, Partly three-dimensional global modeling of a silicon Czochralski furnace. I. Principles, formulation and implementation of the model, International Journal of Heat and Mass Ttransfer, 10.1016/j.ijheatmasstransfer.2005.04.031, 48, 21-22, 4481-4491, 2005.01.
261. Lijun Liu and Koichi Kakimoto, Partly three-dimensional global modeling of a silicon Czochralski furnace.II. Model application: Analysis of a silicon Czochralski furnace in a transverse magnetic field, International Journal of Heat and Mass Transfer, 10.1016/j.ijheatmasstransfer.2005.04.030, 48, 21-22, 4492-4497, 2005.01.
262. Koichi Kakimoto, Lijun Liu, Partly three-dimensional calculation of silicon Czochralski growth with a transverse magnetic field, Journal of Crystal Growth, Vol.303, (2007)135-140, 2007.01.
263. Yoshihiro Kangawa, Koichi Kakimoto, Possibility of AlN growth using Li–Al–N solvent, Journal of Crystal Growth, 10.1016/j.jcrysgro.2010.04.014, 312, 18, 2569-2573, 2010.09, [URL], The possibility of AlN growth using LiAlN solvent was investigated. Based on theoretical prediction, we selected Li3N as a suitable nitrogen source for AlN growth. First, vapor phase epitaxy using Li3N and Al as source materials was performed to confirm the following reaction on the growth surface: Li3NAl=AlN3Li. The results suggest that the reaction proceeds to form AlN on the substrate under appropriate conditions. Next, AlN growth using LiAlN solvent was carried out. The LiAlN solvent was prepared by annealing of mixtures composed of Li3N and Al. The results imply that AlN was formed under an Al-rich condition. Moreover, it was found that Li was swept out from AlN grains during growth. The results suggest that AlN growth using LiAlN solvent might be a key technology to obtain an AlN crystal boule..
264. Yoshihiro Kangawa, Tatsuhito Wakigawa, Koichi Kakimoto, Possibility of AlN solution growth using Al and Li3N, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.1143/JJAP.46.5785, 46, 9 A, 5785-5787, 2007.09, [URL], Suitable nitrogen sources for AlN solution growth were examined. From a theoretical viewpoint, it is speculated that Li3N is suitable for AlN solution growth because the free energy of Li3N formation is larger than that of AlN formation. Nitrogen atoms seem to be transferred from Li3N to Al to form AlN. We performed AlN solution growth using Al and Li3N under an atmospheric pressure of N2. We confirmed the formation of AlN by X-ray diffraction measurement and Raman spectroscopy..
265. Yoshihiro Kangawa, T. Nagano, Koichi Kakimoto, Possibility of AlN vapor phase epitaxy using Li3N as a nitrogen source, Physica Status Solidi (C) Current Topics in Solid State Physics, 10.1002/pssc.200880910, 6, SUPPL. 2, 2009.07, [URL], Possibility of AlN vapor phase epitaxy using Al and Li3N as source materials was investigated. Grown product on sapphire substrate was identified by XRD and Micro-Raman measurements. The results suggest that AlON was formed under Li-N-rich condition though AlN was formed under Al-rich condition. This is because Li3N corroded surface of sapphire and oxygen, which is a constituent element of substrate, was incorporated in the product. Moreover, it is found that AlN nano-wire was formed when excessive Al was supplied during growth. These results imply that it is possible to grow AlN by choosing proper conditions especially Li-N/Al ratio..
266. Xin Liu, Lijun Liu, Zaoyang Li, Yuan Wang, Koichi Kakimoto, Prediction of melt-crystal interface shape and melt convection in a large-scale CZ-Si growth system using RANS and LES methods in global simulation, ISTC/CSTIC 2009 (CISTC)
ECS Transactions - ISTC/CSTIC 2009 (CISTC)
, 10.1149/1.3096561, 18, 983-988, 2009.12, [URL], Global simulations were performed for a large-scale CZ-Si growth system, in which three models were tested to predict the turbulent melt flow. The three turbulence models are the standard k-ε turbulence model using wall functions at solid boundaries, a modified two-layer k-ε turbulence model in RANS method and the standard Smagorinsky SGS model in LES method, respectively. The comparison of the simulation results obtained with these different models showed that each turbulence model has its own features in prediction of the melt convection and the melt-crystal interface shape in a large-scale CZ-Si growth system..
267. W. P. Chen, H. Maeda, Koichi Kakimoto, P. X. Zhang, K. Watanabe, M. Motokawa, Processing of Ag-doped Bi2212 bulks in high magnetic fields
a strong correlation between degree of texture and field strength, Physica C: Superconductivity and its Applications, 10.1016/S0921-4534(99)00320-2, 320, 1, 96-100, 1999.07, [URL], A series of high magnetic fields up to 9 T have been applied to the preparation of Ag-doped Bi2212 bulks and a strong correlation is observed between the field strength and the degree of texture developed in the bulks. Two powders of Bi2.2Sr1.8CuOx and CaCuO2 were synthesized separately and then 10 wt.% Ag was doped to their equimolar mixture, from which the Bi2212 bulks were formed by a partial melt-solidification process in the high magnetic fields. The degree of texture in the bulks was evaluated quantitatively by X-ray diffraction and magnetization measurement. It is found that the applied magnetic fields tend to orient Bi2212 grains with their c-axis parallel to them and obvious texture exists in all samples prepared in the magnetic fields; while in samples prepared without magnetic field Bi2212 grains orient randomly. In the field range of 0-9 T, the degree of texture increases notably with increasing the magnetic field. In 9 T Bi2212, bulks with magnetization anisotropy factor more than four and a density of 6.15 g/cm3 are obtained and SEM observation also shows a highly oriented grain alignment..
268. Yoshihiro Kangawa, Tomonori Ito, Akinori Koukitu, Koichi Kakimoto, Progress in theoretical approach to InGaN and InN epitaxy
In incorporation efficiency and structural stability, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.7567/JJAP.53.100202, 53, 10, 2014.01, [URL], The surface stability, growth process, and structural stability of InGaN and InN are reviewed from a theoretical viewpoint. In 2001, a new theoretical approach based on an ab initio calculation was developed. This theoretical approach enables the investigation of the influence of growth conditions such as partial pressure and temperature on the surface stability. The theoretical approach is applied to the research on the In incorporation efficiency in InGaN grown on nonpolar and semipolar surfaces. The calculation results suggest that the N-H layer formed on such surfaces has a crucial role in In incorporation. Moreover, the structural stability of InN grown by pressurized-reactor MOVPE is reviewed. It was found by the theoretical approach that {11¯1¯} g facet formation causes the spontaneous formation of islands with the zinc-blende structure..
269. Koichi Kakimoto, T. Katoda, Raman spectra from Ga1-xInxAs epitaxial layers grown on GaAs and InP substrates, Applied Physics Letters, 10.1063/1.93281, 40, 9, 826-828, 1982.12, [URL], Raman spectra from Ga1-xInxAs epitaxial layers of various compositions were studied. Both disorder-activated acoustic and optical phonons appeared in the midrange of composition independent of substrate materials. Broadening in the LO phonon due to stress was also observed near the interface region between the epitaxial layer and the substrate when there was lattice mismatch between them even if the amount was as small as 0.7%..
270. Yoji Yamanaka, Koichi Kakimoto, Hiroyuki Ozoe, Stuart W. Churchill, Rayleigh-Benard oscillatory natural convection of liquid gallium heated from below, The Chemical Engineering Journal, 10.1016/S1385-8947(98)00100-4, 71, 3, 201-205, Vol.71, pp.201-205, 1998.12.
271. Yoshihiro Kangawa, Akira Kusaba, Hiroaki Sumiyoshi, Hideto Miyake, Michal Boćkowski, Koichi Kakimoto, Real-time observation system development for high-temperature liquid/solid interfaces and its application to solid-source solution growth of AlN, Applied Physics Express, 10.7567/APEX.8.065601, 8, 6, 2015.01, [URL], Interfacial phenomena at the liquid/solid interface under high temperatures were observed in real time to understand the growth process of AlN during solid-source solution growth. In this study, we used an AlN/α-Al2O3 template as the substrate; these wide-bandgap materials made the substrate transparent to visible light. Therefore, we observed the morphology of the liquid/solid interface through the template from the bottom. In this investigation, a polycrystal formed because of melt-back etching during the initial stage of growth; nevertheless, we succeeded in obtaining real-time images of interfacial phenomena..
272. Koichi Kakimoto, Satoshi Nakano, Recent developments of numerical calculation in crystal growth of SiC, Journal of the Vacuum Society of Japan, 10.3131/jvsj2.60.313, 60, 8, 313-320, 2017.01, [URL], The effect of nitrogen and aluminum as doped impurities on the stability of SiC polytypes (C-or Si-face 4H and 6H substrates) formed by physical vapor transport (PVT) was investigated. The stability of the polytypes was analyzed using classical thermodynamic nucleation theory with numerical results obtained from a global model including heat, mass and species transfer in a PVT furnace. The results reveal that the formation of 4H-SiC was more stable than that of 6H-SiC when a grown crystal was doped with nitrogen using C-face 4H-and 6H-SiC as seed crystals. In contrast, formation of 6H-SiC was favored over 4H-SiC when Si-face 4H-and 6H-SiC seed crystals were used. Meanwhile, the formation of 4H-SiC was more stable than that of 6H-SiC when aluminum was the dopant and C-and Si-faces of 6H-SiC were used as seed crystals. 6H-SiC was preferred to grow rather than 4H-SiC in the cases of C- and Si-faces of 4H-SiC as seed crystals..
273. B. Gao, S. Nakano, Koichi Kakimoto, Reducing impurities of multicrystalline silicon in a unidirectional solidification furnace for solar cells, JOM, 10.1007/s11837-011-0182-3, 63, 10, 43-46, 2011.10, [URL], Multicrystalline silicon has now become the main material in the photovoltaic market because of its low production cost and the relative high conversion efficiency of solar cells made from this material. Effective control of carbon and oxygen impurities in the crystal is required for the production of a high-quality component. In order to reduce impurity levels in a unidirectional solidification furnace, it is proposed to add a crucible cover to the casting process. Results from numerical simulations indicate a marked reduction of carbon impurity in a multicrystalline silicon ingot. The effect of crucible cover material on impurities in multicrystalline silicon was also investigated. These results show that the carbon concentration within the silicon ingot can be reduced by 10 times if the cover is made from carbon and by 1,000 times if the cover is made from tungsten. These results show that an effective and economical method for designing a cover is to use carbon and deposit a thin layer of tungsten on it. Experimental tests have also been carried out by placing a tungsten cover above the crucible. Results indicated that the carbon impurity has significantly decreased; however, the measured carbon concentration in the crystal is larger than the theoretically predicted value, despite the use of a crucible cover. A theoretical analysis has shown that this difference is due to a reaction between the crucible and the graphite susceptor. Furthermore, global simulations have shown that this reaction has a marked effect on carbon and oxygen impurities. When the carbon activity on the surface of the graphite susceptor increases, both oxygen and carbon impurities in crystal increase rapidly. Therefore, the production of high-purity multicrystalline silicon can be improved by designing a crucible cover with a thin layer of tungsten on it and by setting a free space between the silica crucible and the graphite susceptor to prevent reaction between them..
274. Xin Liu, Bing Gao, Satoshi Nakano, Koichi Kakimoto, Reduction of carbon contamination during the melting process of Czochralski silicon crystal growth, Journal of Crystal Growth, 10.1016/j.jcrysgro.2016.12.013, 474, 3-7, 2017.09, [URL], Generation, incorporation, and accumulation of carbon (C) were investigated by transient global simulations of heat and mass transport during the melting process of Czochralski silicon (CZ-Si) crystal growth. Contact reaction between the quartz crucible and graphite susceptor was introduced as an extra origin of C contamination. The contribution of the contact reaction on C accumulation is affected by the back diffusion of C monoxide (CO) from the gap between the gas-guide and the crucible. The effect of the gas-guide coating on C reduction was elucidated by taking the reaction between the silicon carbide (SiC) coating and gaseous Si monoxide (SiO) into account. Application of the SiC coating on the gas-guide could effectively reduce the C contamination because of its higher thermochemical stability relative to that of graphite. Gas flow control on the back diffusion of the generated CO was examined by the parametric study of argon gas flow rate. Generation and back diffusion of CO were both effectively suppressed by the increase in the gas flow rate because of the high Péclet number of species transport. Strategies for C content reduction were discussed by analyzing the mechanisms of C accumulation process. According to the elucidated mechanisms of C accumulation, the final C content depends on the growth duration and contamination flux at the gas/melt interface..
275. Bing Gao, Satoshi Nakano, Koichi Kakimoto, Reduction of oxygen impurity in multicrystalline silicon production, International Journal of Photoenergy, 10.1155/2013/908786, 2013, 2013.03, [URL], Effective control of oxygen impurity in multicrystalline silicon is required for the production of a high-quality crystal. The basic principle and some techniques for reducing oxygen impurity in multicrystalline silicon during the unidirectional solidification process are described in this paper. The oxygen impurity in multicrystalline silicon mainly originates from the silica crucible. To effectively reduce the oxygen impurity, it is essential to reduce the oxygen generation and enhance oxygen evaporation. For reduction of oxygen generation, it is necessary to prevent or weaken any chemical reaction with the crucible, and for the enhancement of oxygen evaporation, it is necessary to control convection direction of the melt and strengthen gas flow above the melt. Global numerical simulation, which includes heat transfer in global furnace, argon gas convection inside furnace, and impurity transport in both melt and gas regions, has been implemented to validate the above methods..
276. B. Gao, S. Nakano, H. Harada, Y. Miyamura, T. Sekiguchi, Koichi Kakimoto, Reduction of polycrystalline grains region near the crucible wall during seeded growth of monocrystalline silicon in a unidirectional solidification furnace, Journal of Crystal Growth, 10.1016/j.jcrysgro.2011.11.084, 352, 1, 47-52, 2012.08, [URL], The generation of polycrystalline grains region near the crucible wall during seeded growth of monocrystalline silicon in a unidirectional solidification furnace was analyzed numerically. The crystal-melt interface is tracked by an enthalpy method. Numerical results show that some polycrystalline silicon grains generates along the crucible wall and marches into the interior of crystal. The ratio of polycrystalline silicon grains in a global crystal is mainly determined by a ratio of thermal flux along the crucible wall to thermal flux along the seed. By reducing the thermal flux along the crucible wall or by increasing the thermal flux along the seed, the ratio of polycrystalline silicon grains in a global crystal can be markedly reduced..
277. Y. Miyamura, H. Harada, S. Nakano, S. Nishizawa, Koichi Kakimoto, Relationship between carbon concentration and carrier lifetime in CZ-Si crystals, Journal of Crystal Growth, 10.1016/j.jcrysgro.2018.01.020, 486, 56-59, 2018.03, [URL], This paper aims to clarify the effect of carbon concentration on carrier lifetime in as-grown n-type and non-doped silicon crystals produced via the Czochralski (CZ) method. We grew n-type and non-doped silicon single crystals with 3-in. diameters along with different carbon and phosphorous contents. The resistivity, concentrations of oxygen and carbon, and lifetime were measured using four-point measurements, Fourier-transform infrared spectroscopy, and the eddy current method, respectively. The oxygen concentrations of the crystals were 6–8 × 1017 atoms/cm3, and the bulk lifetimes ranged from 10 to 20 ms. The carrier lifetime of CZ silicon crystals depended on dopant concentration but had no significant dependence on carbon concentration..
278. Bing Gao, Koichi Kakimoto, Relationship between the locations of activated dislocations and the cooling flux direction in monocrystalline-like silicon grown in the [001] and [111] directions, Journal of Applied Crystallography, 10.1107/S002188981302517X, 46, 6, 1771-1780, 2013.12, [URL], To effectively control dislocations of monocrystalline-like silicon grown in the [001] and [111] directions, the relationship between the locations of activated dislocations and the cooling flux direction was studied numerically from the perspective of activation of slip systems. The cooling flux direction was shown to have a significant effect on the activation of slip systems. The radial flux and axial flux activate different slip systems at different locations in the crystal. The relationship between the flux direction and the activation of slip systems in the [001] and [111] growth directions has been revealed. The results provide theoretical support for reducing dislocations inside a crystal or in the part of the crystal where dislocations can cause the most damage, by intentionally controlling the flux direction during the crystal growth process..
279. S. Nakano, B. Gao, Koichi Kakimoto, Relationship between oxygen impurity distribution in multicrystalline solar cell silicon and the use of top and side heaters during manufacture, Journal of Crystal Growth, 10.1016/j.jcrysgro.2013.04.001, 375, 62-66, 2013.05, [URL], The relationship between the oxygen impurity distribution in multicrystalline silicon and the use of top and/or side heaters in an unidirectional solidification process was investigated by numerical analysis. It was found that the oxygen concentration in the melt for the side heating system is lower than that for only the top heating system. This occurs because of the difference in flow direction of the melt near the crucible wall. The melt flows upward near the crucible wall when the side heating system is used. Oxygen is therefore dissolved from the silica crucible wall and is transported easily to the melt surface, where it evaporates..
280. Tomoro Ide, Hirofumi Harada, Yoshiji Miyamura, Masato Imai, Satoshi Nakano, Koichi Kakimoto, Relationship between dislocation density and oxygen concentration in silicon crystals during directional solidification, Crystals, 10.3390/cryst8060244, 8, 6, 2018.06, [URL], This paper reports the relationship between oxygen concentration and dislocation multiplication in silicon crystals during directional solidification using numerical analysis. Based on the Alexander–Haasen–Sumino model, this analysis involved oxygen diffusion from the bulk to dislocation cores during crystal growth and annealing processes in a furnace. The results showed that the dislocation density mainly increased during cooling process, rather than crystal growth, when the effect of oxygen diffusion to dislocation cores was ignored. On the contrary, the dislocation density increased during both crystal growth and cooling processes when the effect of interstitial oxygen diffusion was considered. At a dislocation density larger than 1.0 × 105 cm–2, the interstitial oxygen concentration in bulk decreased due to the diffusion process, if interstitial oxygen atoms were between dislocations, whereas the concentration at dislocation cores increases..
281. Koichi Kakimoto, Report on the meetings of the international organization for crystal growth executive committee, council and general assembly held during ICCGE-17 in Warsaw (Poland) 11-16 august 2013, Journal of Crystal Growth, 10.1016/j.jcrysgro.2013.09.032, 401, 910-911, 2014.01, [URL], A report of the Report on the Meetings of the International Organization for Crystal Growth Executive Committee, Council and General Assembly held during ICCGE-17 in Warsaw, Poland from August 11-16, 2013 is presented. The results of the IOCG election of officers and executive committee for 2013-2016 term were announced during the event. The winners of the IOCG awards were announced and the IOCG Frank Prize was awarded to Professor Katsuo Tsukamoto for his pioneering investigations with phase-shift interferometry which led to fundamental discoveries in the area of solution- based crystallization under microgravity and on the earth. The Schieber Prize, sponsored by Elsevier, was assigned to Professor Yuki Kimura for his innovative work on the nucleation and growth of cosmic nano-minerals based on size effects of nanoparticles..
282. Zaoyang Li, Lijun Liu, Xiaohong Nan, Koichi Kakimoto, Role of marangoni tension effects on the melt convection in directional solidification process for multi-crystalline silicon ingots, Journal of Crystal Growth, 10.1016/j.jcrysgro.2012.02.031, 346, 1, 40-44, 2012.05, [URL], We carried out global simulations to investigate the marangoni tension effect on the thermal and flow fields in the silicon melt of the directional solidification process for multi-crystalline silicon ingots. The argon flow rate was varied to provide different solidification conditions and to change the relative values between the argon shear stress and the marangoni tension at the melt free surface. We found that the marangoni tension together with the shear stress mainly influences the upper layer melt convection while the thermal buoyancy force dominates the bulk flow of the melt. At low argon flow rates, the argon shear stress can be neglected and the marangoni tension alone enhances the melt convection intensity near the gas-melt-crucible triple junction point. The marangoni tension is so weak that it cannot modify the melt flow pattern in this case. For medium flow rate, the marangoni tension can significantly weaken the shear stress effect at the outer part of the melt free surface, leading to a distinctive flow pattern in the silicon melt. With further increase in argon flow rate, the shear stress sharply increases and dominates the upper layer melt flow, limiting the marangoni tension effect to the triple point. The numerical results are helpful for better understanding and controlling of the directional solidification process for high quality multi-crystalline silicon ingots..
283. Tomoe Yayama, Yoshihiro Kangawa, Koichi Kakimoto, Role of the surface N-H molecular layer in high quality In-RICH InGaN growth by MOVPE, Journal of Chemical Engineering of Japan, 10.1252/jcej.13we309, 47, 7 SPECIAL ISSUE, 615-619, 2014.01, [URL], This study theoretically investigates the influence of the growth orientation on In incorporation during metal-organic vapor phase epitaxy (MOVPE) growth. We propose a new theoretical model based on first-principles calculations that show the role of the N-H molecular layer on In incorporation. Under MOVPE growth conditions, III-nitride surfaces terminated by N-H molecular layers are stable. The N-H layer that covers the In atomic layer prevents In atom desorption and is replaced by Ga atoms. In incorporation is, therefore, more efficient for higher N-H layer coverage and stability. To investigate this relationship, calculation of the enthalpy change for the decomposition of an N-H molecular layer was performed. To take into account the experimental conditions, temperature dependence of surface reconstruction is considered. The trend of this enthalpy change depends on the growth orientation, which agrees well with the experimental In composition..
284. Koichi Kakimoto, Hiroyuki Ozoe, Segregation of oxygen at a solid/liquid interface in silicon, Journal of the Electrochemical Society, 10.1149/1.1838541, 145, 5, 1692-1695, 1998.01, [URL], The incorporation of oxygen into silicon single crystals from the melt is examined in terms of an experiment and a model on a transient solidification. A transient analysis offered an effective segregation coefficient of oxygen in silicon and a diffusion constant of oxygen in the melt almost independently. The analysis estimated these values of effective segregation coefficient of oxygen in silicon and diffusion constant of oxygen in the melt..
285. Koichi Kakimoto, Hiroshi Noguchi, Minoru Eguchi, Sensitivity of oxygen sensors in silicon melt to temperature fluctuation, Journal of the Electrochemical Society, 10.1149/1.1838133, 144, 11, 4045-4049, 1997.01, [URL], The effect of temperature fluctuation in silicon melt on the electromotive force (E) of oxygen sensors was examined by experimental and analytical studies. Two different reference materials, namely, Cr/Cr2O3 and Ni/NiO, were used to clarify how the temperature fluctuation in the melt affects the electromotive force of the sensors. The temperature derivative of the electromotive force (∂E/∂T) of the reference material Cr/Cr2O3 is larger than that of Ni/NiO. The limits of sensors using Cr/Cr2O3 or Ni/NiO as a reference material are discussed from the standpoint of the temperature fluctuation in the melt. The degradation mechanism of the sensors is also discussed. An apparent oxygen partial pressure gradually increased with elapsed time of 40 min from the start of measurement due to the degradation of the sensors. We investigated the cause of the increase of partial pressure based on the metallization of reference materials in the sensors..
286. K. Sato, Y. Furukawa and K. Nakajima,Koichi KAKIMOTO, Si bulk crystal growth: What and how?, Advances in Crystal Growth Research, 10.1016/B978-044450747-1/50036-3, 155-166, pp155-166, 2001.01.
287. Koichi Kakimoto, Bing Gao, Satoshi Nakano, Hirofumi Harada, Yoshiji Miyamura, Silicon bulk growth for solar cells
Science and technology, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.7567/JJAP.56.020101, 56, 2, 2017.02, [URL], The photovoltaic industry is in a phase of rapid expansion, growing by more than 30% per annum over the last few decades. Almost all commercial solar cells presently use single-crystalline or multicrystalline silicon wafers similar to those used in microelectronics; meanwhile, thin-film compounds and alloy solar cells are currently under development. The laboratory performance of these cells, at 26% solar energy conversion efficiency, is now approaching thermodynamic limits, with the challenge being to incorporate these improvements into low-cost commercial products. Improvements in the optical design of cells, particularly in their ability to trap weakly absorbed light, have also led to increasing interest in thin-film cells based on polycrystalline silicon; these cells have advantages over other thin-film photovoltaic candidates. This paper provides an overview of silicon-based solar cell research, especially the development of silicon wafers for solar cells, from the viewpoint of growing both single-crystalline and multicrystalline wafers..
288. K. Kakimoto, L. Liu, T. Kitashima, A. Murakawa and Y. Hashimoto, Silicon crystal growth from the melt: Analysis from atomic and macro scales, Cryst. Res. Technol, 10.1002/crat.200410343, 40, 4-5, 307-312, 2005.01.
289. X. J. Chen, S. Nakano, L. J. Liu, Koichi Kakimoto, Simulation analysis of point defects in a silicon ingot during a unidirectional solidification process for solar cells, ISTC/CSTIC 2009 (CISTC)
ECS Transactions - ISTC/CSTIC 2009 (CISTC)
, 10.1149/1.3096568, 18, 1031-1035, 2009.12, [URL], A transient global model was used to obtain the solution of a thermal field within the entire furnace of a unidirectional solidification process. The melt-solid interface shape was obtained by a dynamic interface tracking method. Then, based on the global solution of heat transfer, the effects of growth rate Vg, temperature gradient G and ratio Vg/G on point defects were analyzed. Finally, several different melt-solid interface shapes were obtained by using different solidification times. Then the effects of solidification time on ratio Vg/G and point defects were also studied..
290. Bing Gao, Satoshi Nakano, Hirofumi Harada, Yoshiji Miyamura, Takashi Sekiguchi, Koichi Kakimoto, Single-Seed Casting Large-Size Monocrystalline Silicon for High-Efficiency and Low-Cost Solar Cells, Engineering, 10.15302/J-ENG-2015032, 1, 3, 378-383, 2015.09, [URL], To grow high-quality and large-size monocrystal-line silicon at low cost, we proposed a single-seed casting technique. To realize this technique, two challenges—polycrystalline nucleation on the crucible wall and dislocation multiplication inside the crystal—needed to be addressed. Numerical analysis was used to develop solutions for these challenges. Based on an optimized furnace structure and operating conditions from numerical analysis, experiments were performed to grow monocrystalline silicon using the single-seed casting technique. The results revealed that this technique is highly superior to the popular high-performance multicrystalline and multiseed casting mono-like techniques..
291. 渡辺匡人, 江口 実, 柿本浩一,日比谷孟俊, Si融液対流の三次元観察 ( Three-dimensional observation of molten silicon convection), 応用物理, 第60巻, 第8号(1991), 799-803, 1991.08, [URL].
292. Kyung Woo Yi, Koichi Kakimoto, Minoru Eguchi, Masahito Watanabe, Toshiyuki Shyo, Taketoshi Hibiya, Spoke patterns on molten silicon in Czochralski system, Journal of Crystal Growth, 10.1016/0022-0248(94)90005-1, 144, 1-2, 20-28, 1994.01, [URL], Asymmetric temperature profiles similar to the spoke patterns and related asymmetric flow in Si melts of the Czochralski (CZ) system are verified for the first time by three-dimensional (3D) numerical simulation of heat and momentum transfer and by X-ray radiography technique. These profiles appear as the temperature difference between the wall and the crystal becomes large with symmetric boundary conditions. The 3D simulation leads to the conclusion that the vertical temperature gradient in the unstable layer near the free surface is an important cause of making the asymmetric profile. The profile is estimated to be caused by both Rayleigh-Bénard and Marangoni-Bénard instabilities in the Si melt. It is shown that the relative strength of these two instabilities depends on the coefficients of temperature dependence of the density and surface tension. If the temperature coefficient of surface tension (∂γ/∂T) is greater than 1 x 10-4 N/m {dot operator}, the Marangoni-Bénard instability mainly causes asymmetry, while if ∂γ/∂T is less than this value, the Rayleigh-Bénard instability mainly causes asymmetry..
293. Koichi Kakimoto, Hiroyuki Konishi, Akimasa Tashiro, Yoshio Hashimoto, Hideo Ishii, Takashige Shinozaki and Kenji Kitamura, Stabilization of Melt Convection of Lithium Niobate Using Accelerated Crucible Rotation Technique, Journal of The Electrochemical Society, 10.1149/1.1566421, 150, 5, J17-J22, 2003.01.
294. Hiroshi Tomonori, Mitsuo Iwamoto, Koichi Kakimoto, Hiroyuki Ozoe, Kenjiro Suzuki, Tsuguo Fukuda, Standing-oscillatory natural convection computed for molten silicon in Czochralski configuration, Chemical Engineering Journal, 10.1016/S1385-8947(98)00115-6, 71, 3, 191-200, 1998.01.
295. Takahiro Kawamura, Mitsutoshi Mizutani, Yasuyuki Suzuki, Yoshihiro Kangawa, Koichi Kakimoto, Strain energy analysis of screw dislocations in 4H-SiC by molecular dynamics, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.7567/JJAP.55.031301, 55, 3, 2016.03, [URL], We simulated screw dislocations with the Burgers vector parallel to the [0001] direction in 4H-SiC by a classical molecular dynamics method. A stable structure of an extended dislocation generated by the dissociation of a screw dislocation was identified by calculating the strain energy caused by dislocation cores and stacking faults. As a result, we conclude that the most expected structure of the extended dislocation is made of partial dislocations with the Burgers vector b = 1/2c + 1/2c (c is equal to the thickness of one period in the c-axis direction of 4H-SiC) and the stacking fault that is parallel to the a-plane, and that the distance between the dislocation cores is less than about 44Å..
296. Yoshihiro Kangawa, Hiroshige Suetsugu, Michael Knetzger, Elke Meissner, Kouji Hazu, Shigefusa F. Chichibu, Takashi Kajiwara, Tanaka Satoru, Yosuke Iwasaki, Koichi Kakimoto, Structural and optical properties of AlN grown by solid source solution growth method, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.7567/JJAP.54.085501, 54, 8, 2015.01, [URL], Structural and optical properties of AlN grown on AlN(0001) by the solid source solution growth (3SG) method were investigated. Transmission electron microscopy (TEM) analysis revealed that the geometrical relationship between the growth directions and slip planes influenced the dislocation propagation behaviors and annihilation mechanisms. Panchromatic and monochromatic images in the cathodoluminescence (CL) spectrum further revealed that C impurities were segregated near the surface, while Al vacancies were widely distributed in the AlN/AlN(0001) grown using the 3SG method..
297. Kyung Woo Yi, Vicki B. Booker, Minoru Eguchi, Toshiyuki Shyo, Koichi Kakimoto, Structure of temperature and velocity fields in the Si melt of a Czochralksi crystal growth system, Journal of Crystal Growth, 10.1016/0022-0248(95)00277-4, 156, 4, 383-392, 1995.12, [URL], Non-axisymmetric temperature and velocity profiles attributed to crucible rotation in the Si melt of a Czochralski (Cz) system were studied numerically by using three-dimensional (3D) numerical simulation and experimentally by measuring temperature. Two types of non-axisymmetric temperature and velocity profiles were found to exist in the melt. The type observed at low rotation rates occurs under conditions in which Rayleigh-Bénard instability occurs, and the other type of non-axisymmetric flow observed at high rotation rates occurs under conditions corresponding to the occurrence of the baroclinic instability in the rotating annulus. The 3D structure of the temperature field was studied experimentally to confirm the possibility of baroclinic instability in the melt. The predominant trend was a tilt of the temperature field in the same direction as crucible rotation. It was found that the temperature field tilted along the azimuthal direction under conditions in which baroclinic instability occurs..
298. T. Shiramomo, B. Gao, F. Mercier, Shinichi Nishizawa, S. Nakano, Koichi Kakimoto, Study of the effect of doped impurities on polytype stability during PVT growth of SiC using 2D nucleation theory, Journal of Crystal Growth, 10.1016/j.jcrysgro.2013.03.036, 385, 95-99, 2014.01, [URL], The effect of nitrogen and aluminum as doped impurities on the stability of SiC polytypes (C- or Si-face 4H and 6H substrates) formed by physical vapor transport (PVT) was investigated. The stability of the polytypes was analyzed using classical thermodynamic nucleation theory with numerical results obtained from a global model including heat, mass and species transfer in a PVT furnace. The results reveal that the formation of 4H-SiC was more stable than that of 6H-SiC when a grown crystal was doped with nitrogen using C-face 4H- and 6H-SiC as seed crystals. In contrast, formation of 6H-SiC was favored over 4H-SiC when Si-face 4H- and 6H-SiC seed crystals were used. Meanwhile, the formation of 4H-SiC was more stable than that of 6H-SiC when aluminum was the dopant and C- and Si-faces of 6H-SiC were used as seed crystals. Formation of 6H-SiC occurred over that of 4H-SiC in the cases of C- and Si-faces of 4H-SiC as seed crystals..
299. M. Matsumoto, H. Harada, K. Kakimoto, J. Yan, Study on Mechanical Properties of Single-Crystal Silicon Carbide by Nanoindentation, Applied Mechanics and Materials, doi:10.4028/www.scientific.net/AMM.806.549, 806, (2015), 549-554, 2015.07.
300. B. Gallien, M. Albaric, T. Duffar, Koichi Kakimoto, M. M'Hamdi, Study on the usage of a commercial software (Comsol-Multiphysics®) for dislocation multiplication model, Journal of Crystal Growth, 10.1016/j.jcrysgro.2016.05.027, 457, 60-64, 2017.01, [URL], Elaboration of silicon ingots for photovoltaic application in Directional Solidification furnace leads to formation of dislocations mainly due to thermoelastic stresses, which impact photovoltaic conversion rate. Several research teams have created numerical simulation models using home-made software in order to study dislocation multiplication and predict the dislocation density and residual stresses inside ingots after elaboration. In this study, the commercial software Comsol-Multiphysics® is used to calculate the evolution of dislocation density during the ingot solidification and cooling. Thermo-elastic stress, due to temperature field inside the ingot during elaboration, is linked to the evolution of the dislocation density by the Alexander and Haasen model (A&H model). The purpose of this study is to show relevance of commercial software to predict dislocation density in ingots. In a first approach, A&H physical model is introduced for a 2D axisymmetric geometry. After a short introduction, modification of Comsol® software is presented in order to include A&H equations. This numerical model calculates dislocation density and plastic stress continuously during ingot solidification and cooling. Results of this model are then compared to home-made simulation created by the teams at Kyushu university and NTNU. Results are also compared to characterization of a silicon ingot elaborated in a gradient freeze furnace. Both of these comparisons shows the relevance of using a commercial code, as Comsol®, to predict dislocations multiplication in a silicon ingot during elaboration..
301. X. J. Chen, S. Nakano, L. J. Liu, Koichi Kakimoto, Study on thermal stress in a silicon ingot during a unidirectional solidification process, Journal of Crystal Growth, 10.1016/j.jcrysgro.2008.07.027, 310, 19, 4330-4335, 2008.09, [URL], A transient global model was used to obtain the solution of a thermal field within the entire furnace during a unidirectional solidification process for photovoltaics. The melt-solid interface shape was obtained by a dynamic interface tracking method. The thermal stress distribution in the silicon ingot was solved using the displacement-based thermo-elastic stress model. Furthermore, several different melt-solid interface shapes were obtained by using different growth velocities, and then the thermal stresses for different solidification times were compared. The simulation results suggested that the crucible constraint should be reduced and a longer solidification time should be used for growing a silicon ingot with low thermal stress and low dislocation density..
302. Tatsuhito Wakigawa, Toshihiko Nagano, Yoshihiro Kangawa, Koichi Kakimoto, Synthesis of AlN from Li3N and Al
Application to vapor phase epitaxy, Journal of Crystal Growth, 10.1016/j.jcrysgro.2008.02.016, 310, 11, 2827-2831, 2008.05, [URL], We performed synthesis of AlN using Al and Li3N. In this method, there are two problems that must be solved for obtaining single-phase AlN. One of them is suppression of Li3AlN2 formation and the other is precipitation of LiAl from the residual source materials during the cooling process. In the present work, we analyzed phase stability of products and found that AlN was stable at high temperatures and low Li-N/Al molar ratios. However, the products still contained LiAl and Al. Therefore, we examined the effectiveness of vapor phase epitaxy for separating AlN from the extra phase (LiAl and Al formed from residual source materials). From the experimental results, feasibility of vapor phase epitaxy was confirmed. That is, we can deposit only an AlN layer on a sapphire substrate by optimizing the growth conditions, i.e., temperature range above 1150 °C and Li-N/Al molar ratio less than 1..
303. Teruaki Katsube, Koichi Kakimoto, Toshiaki Ikoma, Temperature and energy dependences of capture cross sections at surface states in Si metal-oxide-semiconductor diodes measured by deep level transient spectroscopy, Journal of Applied Physics, 10.1063/1.329128, 52, 5, 3504-3508, 1981.12, [URL], A new deep level transient spectroscopy technique is presented to determine capture cross sections at metal-oxide semiconductor (MOS) surface states. The technique enables us to determine energy and temperature dependences of capture cross sections separately. Applying this method, electron capture cross sections at surface states in Si MOS diodes were measured and found to have strong energy dependence and rather weak temperature dependence. It was also found that there was an effect to increase the emission rate, which may be attributed to barrier lowering at the Si-SiO2 interface..
304. Koichi Kakimoto, Taketoshi Hibiya, Temperature dependence of viscosity of molten GaAs by an oscillating cup method, Applied Physics Letters, 10.1063/1.97924, 50, 18, 1249-1250, 1987, [URL], A viscosity measurement system for molten semiconductors has been established by adopting an oscillating cup method. The temperature dependence of viscosity for molten GaAs in the temperature range from near the melting point up to 1480°C was obtained. The viscosity and activation energy of molten GaAs showed a remarkable increase in the vicinity of the melting point (1238°C). The viscosity of molten GaAs decreases with an increase in temperature above 1320°C, with an activation energy of about 0.28 eV..
305. J. Mizuki, Koichi Kakimoto, M. Misawa, T. Fukunaga, N. Watanabe, Temperature dependence studies of the liquid structure of GaSb by neutron diffraction, Journal of Physics Condensed Matter, 10.1088/0953-8984/5/21/001, 5, 21, 3391-3396, 1993.12, [URL], The liquid structure of GaSb has been investigated by neutron diffraction for temperatures ranging from 800 to 1050 degrees C. In contrast with expectations from viscosity measurements, no drastic change in structure was observed over this temperature range. However, the structure factor S(Q) presented a shoulder on the high-Q side of its first peak at all temperatures, suggesting the existence of short-range ordering in the molten state. The radial distribution function shows 5.4+or-0.5 atoms up to the second-nearest neighbours. The data can be explained by a structural model based on beta -Sn-like short-range order. The anomalous temperature dependence of the viscosity is also discussed with this structural model of the molten state..
306. Koichi Kakimoto, Hisao Watanabe, Taketoshi Hibiya, Temperature fluctuation in molten GaAs, Journal of the Electrochemical Society, 10.1149/1.2108496, 133, 12, 2649-2652, 1986, [URL], Using a thermocouple immersed into the melt, temperature fluctuation in molten GaAs was directly measured over a temperature ranging from 160 K above to 28 K below the melting point; temperature fluctuation in the melt was observed even for supercooled melts. Melt viscosity was estimated from the temperature fluctuation. Melt viscosity increased nonlogarithmically vs. temperature under the supercooled condition. It could be inferred that a short range ordering, such as second and/or third nearest neighbor atoms ordering, was formed around the melting point..
307. Shin Nakamura, Taketoshi Hibiya, Koichi Kakimoto, Nobuyuki Imaishi, Shinichi Nishizawa, Akira Hirata, Kusuhiro Mukai, Shin Ichi Yoda, Tomoji S. Morita, Temperature fluctuations of the Marangoni flow in a liquid bridge of molten silicon under microgravity on board the TR-IA-4 rocket, Journal of Crystal Growth, 10.1016/S0022-0248(97)00440-5, 186, 1-2, 85-94, 1998.03, [URL], Temperature fluctuation measurements in a liquid bridge of molten silicon, which shows the Marangoni flow in highly super-critical condition, are performed in a half-zone configuration under microgravity on board a TR-IA-4 rocket and on the ground. In the microgravity experiment, two types of temperature oscillation are observed during the melting process of silicon and in the cylindrical half-zone melt. The former oscillation, which has a frequency of about 0.1 Hz during the melting process, has an antiphase correlation of temperature oscillation measured in thermocouples separated by 90° azimuthal angles. The latter oscillation in the cylindrical liquid bridge has no remarkable frequency; however, it tends to have the antiphase correlation in between thermocouples with 180° azimuthal angles. In the ground experiment, temperature fluctuations have a characteristic frequency of 0.2 Hz and there is an antiphase correlation of temperatures in thermocouples with 180° azimuthal angles by using the slender melt zone..
308. W. P. Chen, H. Maeda, Koichi Kakimoto, P. X. Zhang, K. Watanabe, M. Motokawa, H. Kumakura, K. Itoh, Textured crystal growth of Bi(Pb)2212 bulk ceramics in high magnetic field, Journal of Crystal Growth, 10.1016/S0022-0248(99)00167-0, 204, 1, 69-77, 1999.07, [URL], A systematic investigation has been made on the textured crystal growth of Bi(Pb)2212 bulk ceramics in high magnetic field. According to X-ray diffraction and microstructure analysis, a 9 T magnetic field is found to have an obvious tendency to orient Bi(Pb)2212 grains with their c-axis parallel to it in magnetic melt process (MMP). Bi(Pb)2212 single-phased bulk ceramics with an anisotropy of a factor of two in magnetization can be obtained by MMP while the microstructure and superconducting properties of the ceramics depend greatly on the preparing process. A two-step synthesis method, in which Bi(Pb)2212 is formed by the reaction between Bi(Pb)2201 and CaCuO2 powders in partial melting, is found especially useful for improving the density of the ceramics solidified from partial melting. The grain coupling strength and the crystal growth is also influenced greatly by the temperature profile of heat treatment, especially by the cooling rate during solidification and the maximum temperature in partial melting..
309. Koichi Kakimoto, Watanabe Masahito, Eguchi Minoru, Hibiya Taketoshi, The Coriolis force effect on molten silicon convection in a rotating crucible, International Journal of Heat and Mass Transfer, 10.1016/0017-9310(92)90096-B, 35, 10, 2551-2555, 1992.01, [URL], Silicon single crystals are usually grown from melt in a rotating crucible by the Czochralski method. The purpose of the present paper is to make the velocity profile in the azimuthal direction clear. The flow velocity profile has been obtained from numerical simulation and flow visualization by X-ray radiography. Numerical simulation and experimental flow visualization have made it clear that the flow in the azimuthal direction is modulated by the Coriolis force because the radial flow velocity is relatively high. The azimuthal flow velocity near a crucible wall has a smaller (or negative) value compared with the angular velocity of the crucible, while the flow with a larger azimuthal velocity exists in the center of the crucible..
310. Lijun Liu, Tomonori Kitashima and Koichi Kakimoto, The Effects of Magnetic Fields on Melt Convection in Czochralski Silicon Growth Analyzed by 3D Global Calculation, Computational mechanics, WCCM VI in conjunction with APCOM’04, 2004.01.
311. Masahito Watanabe, Minoru Eguchi, Koichi Kakimoto, Yann Baros, Taketoshi Hibiya, The baroclinic flow instability in rotating silicon melt, Journal of Crystal Growth, 10.1016/0022-0248(93)90335-T, 128, 1-4, 288-292, 1993.03, [URL], Three-dimensional flow visualization experiments were used to observe the transition from axisymmetric to non-axisymmetric flow of molten silicon in the CZ crystal growth configuration at specific crucible rotation rates. Non-axisymmetric flow shows characteristics of the baroclinic instability when the flow pattern is observed from a rotating viewpoint. The transition from axisymmetric to non-axisymmetric flow due to the baroclinic instability is characterized by using two non-dimensional numbers, the Thermal Rossby number (Rot) and the Taylor number (Ta)..
312. H. Fukui, Koichi Kakimoto, H. Ozoe, The convection under an axial magnetic field in a Czochralski configuration, Proceedings of the 1998 5th International Conference on Advanced Computational Methods in Heat Transfer
Proceedings of the International Conference on Advanced Computational Methods in Heat Transfer
, 135-144, 1998.06, Numerical computations were carried out for the mixed convection of liquid metal in a Czochralski configuration under an axial magnetic field. A crystal rod was rotated and a crucible static. For a static crucible, an application of an axial magnetic field yielded a rotation of a fluid column under a crystal rod. This was due to complicated effects of a Lorentz force..
313. Yuren Wang and Koichi Kakimoto, The dislocation behaviour in the vicinity of molten zone : An X-ray topography study of the melting of silicon, Eleventh American Conference on Crystal Growth & Epitaxy(ACCGE-11),, p. 106, 1999.08.
314. B. Gao, S. Nakano, Koichi Kakimoto, The impact of pressure and temperature on growth rate and layer uniformity in the sublimation growth of AlN crystals, Journal of Crystal Growth, 10.1016/j.jcrysgro.2011.11.030, 338, 1, 69-74, 2012.01, [URL], To effectively design a large furnace for producing large-size AlN crystals, a fully coupled compressible flow solver was developed to study the sublimation and mass transport processes in AlN crystal growth. Compressible effect, buoyancy effects, flow coupling between aluminum gas and nitrogen gas, and Stefan effect are included. Two sets of experimental data were used to validate the present solver. Simulation results showed that the distributions of Al and N 2 partial pressures are opposite along the axial direction due to constant total pressure and Stefan effect, with the Al and nitrogen partial pressures being highest at the source and seed crystals positions, respectively. The distributions of species inside the growth chamber are obviously two-dimensional, which can curve a flat crystal surface. Simulation results also showed that AlN crystal growth rate can be increased by reducing total pressure or by increasing seed temperature or by increasing source-seed temperature difference. High nitrogen pressure causes decrease in growth rate, but it is beneficial for obtaining uniform growth rate in the radial direction. Results of simulation also showed that there is an optimized temperature difference (40 °C) in the present furnace for obtaining good homogeneity of growth rate..
315. Yuren Wang and Koichi Kakimoto, The shape of solid-melt interface estimated from in-situ X-ray topograph observation, Proceedings of the Fourth Symposium on Atomic-scale Surface and Interface Dynamics, pp.95-100, 2000.03.
316. Tomoe Yayama, Yoshihiro Kangawa, Koichi Kakimoto, Akinori Koukitu, Theoretical analyses of in incorporation and compositional instability in coherently grown InGaN thin films, Physica Status Solidi (C) Current Topics in Solid State Physics, 10.1002/pssc.200983475, 7, 7-8, 2249-2251, 2010.08, [URL], We performed thermodynamic analyses to calculate the relationship between the input indium molar ratio and solid composition of a coherently grown InGaN thin film that is subjected compressive or tensile stress. The theoretical approach incorporates energy loss of a thin film system due to lattice constraint from the substrate. The results show that the indium composition x of coherently grown InGaN is lower than that of stress-free InGaN. This represents the composition pulling effect. We also studied stable growth modes under various growth conditions. The results suggest the importance of control of partial pressure of NH3 to optimize growth conditions of InGaN with a unique composition..
317. Y. Kangawa, Y. Matsuo, T. Akiyama, T. Ito, K. Shiraishi, K. Kakimoto, Theoretical approach to initial growth kinetics of GaN on GaN(001), Journal of Crystal Growth, Vol.300, (2007) 62-65., 2006.12.
318. Akira Kusaba, Yoshihiro Kangawa, Yoshio Honda, Hiroshi Amano, Koichi Kakimoto, Theoretical approach to surface reconstruction of InN(0001) during raised-pressure metalorganic vapor-phase epitaxy, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.7567/JJAP.55.05FM01, 55, 5, 2016.05, [URL], We investigated the surface reconstruction of InN(0001) during raised-pressure metalorganic vapor-phase epitaxy using an ab initio-based approach. We observed that the reconstructed structure changes from In-rich surfaces such as In bilayer and monolayer surfaces to an ideal surface with increasing growth temperature. In addition, we investigated the effects of surface reconstruction on the growth process using a newly improved thermodynamic analysis method. Although no barrier is present in the growth reaction when the In-rich surfaces appear, the results suggest that the surface phase acts as a barrier in the growth reaction when the ideal surface appears. Furthermore, we discuss the growth conditions that enable high-temperature growth with a smooth reaction path..
319. Yoshihiro Kangawa, T. Akiyama, T. Ito, K. Shiraishi, Koichi Kakimoto, Theoretical approach to structural stability of GaN
How to grow cubic GaN, Journal of Crystal Growth, 10.1016/j.jcrysgro.2009.01.117, 311, 10, 3106-3109, 2009.05, [URL], We investigated the growth conditions of cubic GaN (c-GaN) by ab initio-based approach which incorporates free energy of vapor phase. It is known that a c-GaN is a metastable phase and wurtzite GaN (h-GaN), which is a stable phase of GaN, is easily incorporated in the c-GaN crystal during growth. h-GaN is formed in the area grown on {1 1 1} faceted surface. In the present study, therefore, we studied the growth conditions of {1 1 1} facet formation in order to suppress h-GaN mixing. The results suggest that we can suppress the {1 1 1} facet formation, i.e., h-GaN mixing, by controlling the growth conditions such as temperature and gallium beam equivalent pressure..
320. Tomoe Yayama, Yoshihiro Kangawa, Koichi Kakimoto, Theoretical investigation of the effect of growth orientation on indium incorporation efficiency during InGaN thin film growth by metal-organic vapor phase epitaxy, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.7567/JJAP.52.08JC02, 52, 8 PART 2, 2013.08, [URL], The effect of growth orientation on In incorporation efficiency in InGaN films grown by metal-organic vapor phase epitaxy (MOVPE) is theoretically investigated. We propose a new theoretical model that explains the role of the surface N-H layer in In incorporation based on first-principles calculations. During III-nitride MOVPE, N-terminated reconstruction with N dangling bonds passivated by H is stable. A surface N-H layer that covers a group-III (In, Ga) atomic layer prevents In atoms from desorbing and being replaced by Ga atoms. In incorporation is therefore more efficient for higher N-H layer coverage and stability. To investigate this relationship, the enthalpy change for the decomposition of a N-H layer was calculated. This enthalpy change which depends on growth orientations is in good agreement with the experimental In content..
321. Yuya Inatomi, Yoshihiro Kangawa, Tomonori Ito, Tadeusz Suski, Yoshinao Kumagai, Koichi Kakimoto, Akinori Koukitu, Theoretical study of the composition pulling effect in InGaN metalorganic vapor-phase epitaxy growth, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.7567/JJAP.56.078003, 56, 7, 2017.07, [URL], The composition pulling effect in metalorganic vapor-phase InGaN epitaxy was theoretically investigated by thermodynamic analysis. The excess energies of biaxial-strained InxGa1-xN were numerically calculated using empirical interatomic potentials considering different situations: (i) coherent growth on GaN(0001), (ii) coherent growth on In0.2Ga0.8N(0001), and (iii) bulk growth. Using the excess energies, the excess chemical potentials of InN and GaN alloys were computed. Our results show that compressive strain suppresses In incorporation, whereas tensile strain promotes it. Moreover, assuming chemical equilibrium, the relationship between the solid composition and the growth conditions was predicted. The results successfully reproduced the typical composition pulling effect..
322. Takahiro Kawamura, Daisuke Hori, Yoshihiro Kangawa, Koichi Kakimoto, Masashi Yoshimura, Yusuke Mori, Thermal conductivity of SiC calculated by molecular dynamics, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.1143/JJAP.47.8898, 47, 12, 8898-8901, 2008.12, [URL], We calculated the thermal conductivity of SiC by molecular dynamics simulation and investigated the effects of impurities on the thermal conductivity of SiC. We used Tersoff potential to express the structure of a SiC crystal. Thermal conductivity was obtained using Green-Kubo's equation. The results show that the thermal conductivities of perfect 2H-, 3C-, 4H-, and 6H-SiC polytypes were in the range of 260 to 420 W/(m·K) and that the thermal conductivity of 3C-SiC was the largest among the polytypes. The thermal conductivities of 4H-SiC decreased with an increase in impurity concentration above 1.0 × 1017 to 1.0 × 1018 1/cm 3..
323. Karolin Jiptner, Bing Gao, Hirofumi Harada, Yoshiji Miyamura, Masayuki Fukuzawa, Koichi Kakimoto, Takashi Sekiguchi, Thermal stress induced dislocation distribution in directional solidification of Si for PV application, Journal of Crystal Growth, 10.1016/j.jcrysgro.2014.09.017, 408, 1-17, 2014.12, [URL], This paper presents the limitation of the cast technique for silicon growth and the obstacle to reduce the dislocation density below 103 cm-2. The thermal stress induced dislocation density, independent of other dislocation sources, is determined and the result suggests that local dislocation densities as high as 104 cm-2 are readily introduced alone in the cooling period of the crystal growth. Areas of high residual strain and dislocation densities are identified and presented. The experimental results are correlated with numerical simulation based on a three-dimensional Haasen-Alexander-Sumino (HAS) model. The dislocation introduction is caused by an activation of different slip systems in different ingot areas..
324. Akira Nagaoka, Kenji Yoshino, Kenta Aoyagi, Takashi Minemoto, Yoshitaro Nose, Tomoyasu Taniyama, Koichi Kakimoto, Hideto Miyake, Thermo-physical properties of Cu2ZnSnS4 single crystal, Journal of Crystal Growth, 10.1016/j.jcrysgro.2013.11.077, 393, 167-170, 2014.05, [URL], The thermo-physical properties of quaternary compound Cu 2ZnSnS4 (CZTS) have been evaluated from high-quality single crystals grown by the solution method. The Debye temperature, one of the important properties, was determined from the measured heat capacity value below 7 K using the Debye function. The experimental Debye temperature is 302 K, which is a reference value for the thermo-physical understanding of CZTS. The present result can be used to stimulate future experimental and theoretical work..
325. Kazuki Sekiguchi, Hiroki Shirakawa, Kenta Chokawa, Masaaki Araidai, Yoshihiro Kangawa, Koichi Kakimoto, Kenji Shiraishi, Thermodynamic analysis of trimethylgallium decomposition during GaN metal organic vapor phase epitaxy, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.7567/JJAP.57.04FJ03, 57, 4, 2018.04, [URL], We analyzed the decomposition of Ga(CH3)3 (TMG) during the metal organic vapor phase epitaxy (MOVPE) of GaN on the basis of first-principles calculations and thermodynamic analysis. We performed activation energy calculations of TMG decomposition and determined the main reaction processes of TMG during GaN MOVPE. We found that TMG reacts with the H2 carrier gas and that (CH3)2GaH is generated after the desorption of the methyl group. Next, (CH3)2GaH decomposes into (CH3)GaH2 and this decomposes into GaH3. Finally, GaH3 becomes GaH. In the MOVPE growth of GaN, TMG decomposes into GaH by the successive desorption of its methyl groups. The results presented here concur with recent highresolution mass spectroscopy results..
326. Akira Kusaba, Yoshihiro Kangawa, Pawel Kempisty, Hubert Valencia, Kenji Shiraishi, Yoshinao Kumagai, Koichi Kakimoto, Akinori Koukitu, Thermodynamic analysis of (0001) and (0001) GaN metalorganic vapor phase epitaxy, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.7567/JJAP.56.070304, 56, 7, 2017.07, [URL], We performed a thermodynamic analysis of GaN metalorganic vapor phase epitaxy considering the (0001) and (0001) surface states. Surface reconstruction, which depends on growth conditions such as temperature and partial pressure, affects growth processes. To discuss the effects of surface states on growth processes, we investigated the driving force of precursor deposition to form the surface phase defined stoichiometrically. In both N2 and H2 carrier gas cases, we showed surface phase diagrams, calculated driving forces, and discussed the difference in growth orientation..
327. Jun Kawano, Yoshihiro Kangawa, Tomoe Yayama, Koichi Kakimoto, Akinori Koukitu, Thermodynamic analysis of coherently grown GaAsN/Ge
Effects of different gaseous sources, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.7567/JJAP.52.045601, 52, 4 PART 1, 2013.04, [URL], Thermodynamic analysis of coherently grown GaAs1-xNx on Ge with low N content was performed to determine the relationship between solid composition and growth conditions. In this study, a new algorithm for the simulation code, which is applicable to wider combinations of gaseous sources than the traditional algorithm, was developed to determine the influence of different gaseous sources on N incorporation. Using this code here we successfully compared two cases: one is a system using trimethylgallium (TMG), AsH3, and NH3, and the other uses dimethylhydrazine (DMHy) instead of NH3. It was found that the optimal N/As ratio of input gas in the system using DMHy was much lower than that using NH3. This shows that the newly developed algorithm could be a useful tool for analyzing the N incorporation during the vapor growth of GaAs1-xNx..
328. Kawano Jun, Yoshihiro Kangawa, Ito Tomonori, Koichi Kakimoto, Koukitu Akinori, Thermodynamic analysis of vapor-phase epitaxial growth of GaAsN on Ge, Journal of Crystal Growth, 10.1016/j.jcrysgro.2011.12.079, 343, 1, 105-109, 2012.03, [URL], In this paper, we use thermodynamic analysis to determine how the nitrogen (N) ratio in the source gases affects the solid composition of coherently grown GaAs1-xNx(x∼0.03). The source gases for Ga, As, and N are trimethylgallium ((CH3)3Ga), arsine (AsH3), and ammonia (NH3), respectively. The growth occurs on a Ge substrate, and the analysis includes the stress from the substratecrystal lattice mismatch. Calculation results indicate that to have just a few percent N incorporation into the grown solid, the V/III ratio in the source gases should be several thousands and the input-gas partial-pressure ratio NH 3/(NH3AsH3) should exceed 0.99. We also find that the lattice mismatch stress from the Ge substrate increases the V/III sourcegas ratio required for stable growth, whereas an increase in input Ga partial pressure ratio has the opposite effect..
329. Jun Kawano, Yoshihiro Kangawa, Tomoe Yayama, Tomonori Ito, Koichi Kakimoto, Akinori Koukitu, Thermodynamic analysis for the prediction of N composition in coherently grown GaAsN for a multi-junction solar cell, 37th IEEE Photovoltaic Specialists Conference, PVSC 2011
Program - 37th IEEE Photovoltaic Specialists Conference, PVSC 2011
, 10.1109/PVSC.2011.6186002, 496-500, 2011.12, [URL], Thermodynamic analysis was performed to investigate the coherent growth of GaAs 1-xN x thin films with low N content. In the present study, a new algorithm of the simulation code was developed to theoretically predict the relationship between solid composition and growth condition. This algorithm is applicable to wider varieties of combinations of gaseous sources than is the traditional algorithm. The system using trimethylgalllium (TMG), AsH 3, and NH 3 was analyzed with the new code, and the results showed that the required input partial pressure ratio of NH 3 to the group-V element is over 99% for incorporation of a small percent of N into a solid. It is difficult to incorporate N into the solid when the input V/III ratio is low, while in the case of a high input V/III ratio, stable growth with a small percent of N can proceed. In the case of coherently grown GaAs 1-xN x, the lattice constraint from the substrate would suppress the incorporation of nitrogen. On the other hand, a higher input Ga partial pressure ratio enhances the stable growth of GaAs 1-xN x with a small N content, though this condition tends to easily induce generation of dislocations. Furthermore, a much lower optimum N/As ratio in input gas can be achieved in the system with dimethylhydrazine (DMHy). This result confirms that the difference in gaseous sources has a great effect on N incorporation. When determining well-optimized experimental growth conditions, these influences including crystallinity should all be considered..
330. Koichi Kakimoto, B. Gao, T. Shiramomo, S. Nakano, Shinichi Nishizawa, Thermodynamic analysis of SiC polytype growth by physical vapor transport method, Journal of Crystal Growth, 10.1016/j.jcrysgro.2011.03.059, 324, 1, 78-81, 2011.06, [URL], Crystal growth of a certain polytype of SiC in a process of physical vapor transport was studied on the basis of classical thermodynamic nucleation theory in conjunction with numerical results obtained from a global model. Formation of a certain polytype in the nucleation stage is determined by the energy balance among surface energy, formation energy and supersaturation. The preferential growth condition of a certain polytype was estimated. The value of supersaturation was estimated using a numerical model obtained by a global model that includes species transport as well as heat transport in a furnace. The results of calculation showed that 4H polytype is more stable than 15R, 6H and 3C polytypes. Free energy difference between 4H and 6H polytypes decreased when total pressure in the furnace decreased..
331. Kazuki Sekiguchi, Hiroki Shirakawa, Kenta Chokawa, Masaaki Araidai, Yoshihiro Kangawa, Koichi Kakimoto, Kenji Shiraishi, Thermodynamic considerations of the vapor phase reactions in III-nitride metal organic vapor phase epitaxy, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.7567/JJAP.56.04CJ04, 56, 4, 2017.04, [URL], We analyzed the metal organic vapor phase epitaxial growth mechanism of the III-nitride semiconductors GaN, AlN, and InN by first-principles calculations and thermodynamic analyses. In these analyses, we investigated the decomposition processes of the group III source gases X(CH3)3 (X = Ga, Al, In) at finite temperatures and determined whether the (CH3)2GaNH2 adduct can be formed or not. The results of our calculations show that the (CH3)2GaNH2 adduct cannot be formed in the gas phase in GaN metal organic vapor phase epitaxy (MOVPE), whereas, in AlN MOVPE, the formation of the (CH3)2AlNH2 adduct in the gas phase is exclusive. In the case of GaN MOVPE, trimethylgallium (TMG, [Ga(CH3)3]) decomposition into Ga gas on the growth surface with the assistance of H2 carrier gas, instead of the formation of the (CH3)2GaNH2 adduct, occurs almost exclusively. Moreover, in the case of InN MOVPE, the formation of the (CH3)2InNH2 adduct does not occur and it is relatively easy to produce In gas even without H2 in the carrier gas..
332. Yoshihiro Kangawa, Koichi Kakimoto, Tomonori Ito, and Akinori Koukitu, Thermodynamic stability of In1-x-yGaxAlyN on GaN and InN, phys. stat. sol., 2006.01.
333. T. Shiramomo, B. Gao, F. Mercier, Shinichi Nishizawa, S. Nakano, Yoshihiro Kangawa, Koichi Kakimoto, Thermodynamical analysis of polytype stability during PVT growth of SiC using 2D nucleation theory, Journal of Crystal Growth, 10.1016/j.jcrysgro.2012.01.023, 352, 1, 177-180, 2012.08, [URL], We studied dependence of process parameters, such as temperature of a seed, pressure in a furnace and surface polarity of a substrate, on polytypes of SiC in a process of physical vapor transport. The analysis was based on a classical thermodynamic nucleation theory in conjunction with numerical results obtained from a global model. We investigated which polytype was more stable in the nucleation stage by a comparison of nucleation energies of each polytype. The results show that the formation of 4H-SiC was more stable than that of 6H-SiC when we used C-face SiC as a seed. Furthermore, the most stable polytype could change from 4H-SiC to 6H-SiC in a condition of higher supersaturation, with a condition of higher temperature of a seed and lower pressure in a furnace. Meanwhile, the formation of 6H-SiC was more stable than 4H-SiC when Si-face of a seed was used..
334. Hitoshi Matsuo, R. Bairava Ganesh, Satoshi Nakano, Lijun Liu, Yoshihiro Kangawa, Koji Arafune, Yoshio Ohshita, Masafumi Yamaguchi, Koichi Kakimoto, Thermodynamical analysis of oxygen incorporation from a quartz crucible during solidification of multicrystalline silicon for solar cell, Journal of Crystal Growth, 10.1016/j.jcrysgro.2008.08.045, 310, 22, 4666-4671, 2008.11, [URL], We proposed an oxygen transport model in which the reaction between a liner made of Si3N4 and a crucible made of SiO2 was taken into account to study the mechanism of oxygen incorporation in multicrystalline silicon for a solar cell grown by the unidirectional solidification method. The equilibrium oxygen concentration in the case of the unidirectional solidification method was calculated by taking into account the two interfaces between a quartz crucible and a liner of Si3N4 and between a liner of Si3N4 and silicon melt. The calculated equilibrium oxygen concentration was less than half of that in the case of the Czochralski method, in which oxygen was directly dissolved from a quartz crucible into the melt. We also calculated the distribution of oxygen concentration in a silicon crystal by using numerical calculation with global modeling. The equilibrium concentrations of oxygen in the two cases were used as boundary conditions at the interface between silicon melt and quartz crucible in the numerical calculation. The results of numerical calculation by taking into account the Si3N4 coating were found to be close to the experimental results. From these results, we concluded that oxygen was incorporated from a quartz crucible into the melt through the coating material of Si3N4 during the growth process..
335. B. Gao, S. Nakano, H. Harada, Y. Miyamura, Koichi Kakimoto, Three-dimensional analysis of dislocation multiplication during thermal process of grown silicon with different orientations, Journal of Crystal Growth, 10.1016/j.jcrysgro.2016.12.059, 474, 121-129, 2017.09, [URL], We used an advanced 3D model to study the effect of crystal orientation on the dislocation multiplication in single-crystal silicon under accurate control of the cooling history of temperature. The incorporation of the anisotropy effect of the crystal lattice into the model has been explained in detail, and an algorithm for accurate control of the temperature in the furnace has also been presented. This solver can dynamically track the history of dislocation generation for different orientations during thermal processing of single-crystal silicon. Four orientations, [001], [110], [111], and [112], have been examined, and the comparison of dislocation distributions has been provided..
336. B. Gao, Koichi Kakimoto, Three-dimensional analysis of dislocation multiplication in single-crystal silicon under accurate control of cooling history of temperature, Journal of Crystal Growth, 10.1016/j.jcrysgro.2014.03.034, 396, 7-13, 2014.06, [URL], Dislocation multiplication in single-crystal silicon during heating and cooling processes was studied by three-dimensional simulation under accurate control of the temperature history. Three different cooling temperature histories were designed. The results showed that the cooling rate in the high-temperature region has a large effect on the final dislocations and residual stress. The most effective method to reduce dislocations is to use a slow cooling rate in the high-temperature region..
337. Lijun Liu, Satoshi Nakano, Koichi Kakimoto, Three-dimensional global modeling of a unidirectional solidification furnace with square crucibles, Journal of Crystal Growth, 303 (2007) 165-169., 2007.05.
338. Xuejiang Chen, Satoshi Nakano, Koichi Kakimoto, Three-dimensional global analysis of thermal stress and dislocations in a silicon ingot during a unidirectional solidification process with a square crucible, Journal of Crystal Growth, 10.1016/j.jcrysgro.2010.08.045, 312, 22, 3261-3266, 2010.11, [URL], A three-dimensional global model was used to obtain the solution of a thermal field within the entire furnace during a unidirectional solidification process of multicrystalline silicon with a square crucible. Then the thermal stress distribution in the silicon ingot was solved. Based on the solution of thermal stress, relaxation of stress and multiplication of dislocations were performed by using the HaasenAlexanderSumino model (HAS model). The influence of crucible constraint on stress levels and dislocations was investigated. It was found that the crucible constraint had significant influence on the thermal stresses and dislocations in the ingot. The results indicated that it is important to reduce the crucible constraint in order to relax thermal stresses and reduce dislocations in a silicon ingot during the solidification process..
339. Bing Gao, Koichi Kakimoto, Three-dimensional modeling of basal plane dislocations in 4H-SiC single crystals grown by the physical vapor transport method, Crystal Growth and Design, 10.1021/cg401789g, 14, 3, 1272-1278, 2014.03, [URL], To effectively reduce basal plane dislocations (BPDs) during SiC physical vapor transport growth, a three-dimensional model for tracking the multiplication of BPDs has been developed. The distribution of BPDs inside global crystals has been shown. The effects of the convexity of the growth surface and the cooling rate have been analyzed. The results show that the convexity of the growth surface is unfavorable and can cause a large multiplication of BPDs when the crystal grows. Fast cooling during the cooling process is beneficial for the reduction of BPDs because fast cooling can result in a smaller radial flux at the high-temperature region. In addition, fast cooling can reduce the generation of stacking faults during the cooling process. Therefore, to reduce BPDs and stacking faults, it is better to maintain or reduce the convexity of the growth surface and increase the cooling rate during the cooling process..
340. Masahito Watanabe, Minoru Eguchi, Koichi Kakimoto, Taketoshi Hibiya, Three-dimensional visualization of molten silicon convection, Winter Annual Meeting of the American Society of Mechanical Engineers
Experimental and Numerical Flow Visualization
, 128, 255-260, 1991, Molten silicon convection during single crystal growth by the Czochralski method was visualized three-dimensionally by the individually developed double-beam X-ray radiography system with solid tracer method. The purpose of the present paper is to clarify the three-dimensional structure of torus-like flow pattern of molten silicon which has low Prandtl number. The root-mean-square velocity for one specific tracer was 21 mm/sec. The most impressive result was as follows; a flow field with larger azimuthal velocity than the rotational velocity of the crucible exists just beneath the crystal, while the flow field with smaller or negative azimuthal velocity exists near the crucible wall. This azimuthal flow modulation can be explained by the Coriolis force..
341. Masato Inoue, Yoshihiro Kangawa, Katsunori Wakabayashi, Hiroyuki Kageshima, Koichi Kakimoto, Tight-binding approach to initial stage of the graphitization process on a vicinal SiC surface, Japanese Journal of Applied Physics, Part 1: Regular Papers & Short Notes, 10.1143/JJAP.50.038003, 50, 3, 2011.03, [URL], We study the process of growth of graphene by the SiC surface decomposition method to improve the technique of growing graphene. In thisstudy, the initial stage of the graphitization process on a periodically faceted SiC surface is investigated by the Naval Research Laboratory tightbinding approach. The results suggest that the decomposition of the SiC surface started by the desorption of Si atoms at the step edge. It is alsofound that released C atoms are trapped at the step-edge sites and that neighboring Si atoms are subsequently desorbed. These results suggest that graphene nucleation on the SiC surface proceeds in a negative step-flow mode..
342. S. Araki, B. Gao, Shinichi Nishizawa, S. Nakano, Koichi Kakimoto, Total pressure-controlled PVT SiC growth for polytype stability during using 2D nucleation theory, Crystal Research and Technology, 10.1002/crat.201500344, 51, 5, 344-348, 2016.05, [URL], A total pressure-controlled physical vapor transport growth method that stabilizes SiC polytype is proposed. The supersaturation of carbon during SiC growth changed as a function of the growth time due to changes in the temperature difference between the surfaces of the source and the grown crystal. Supersaturation also varied as a function of the pressure inside the furnace. Therefore, modification of the pressure as a function of growth time allowed for constant supersaturation during growth. The supersaturation was calculated based on classical thermodynamic nucleation theory using data for heat and species of Si2C and SiC2 transfer in a furnace obtained from a global model. Based on this analysis, a method for polytype-stabilized SiC growth was proposed that involves decreasing the pressure as a function of growth time. The 4H-SiC prepared using this pressure-controlled method was more stable than that of 4H-SiC formed using the conventional constant-pressure method..
343. Yoo Cheol Won, Koichi Kakimoto and Hiroyuki Ozoe, Transient analysis of melt flow under inhomogeneous magnetic fields, The Second Symposium on Atomic-scale Surface and Interface Dynamics, pp.57-62, 1998.02.
344. Yoo Cheol Won, Koichi Kakimoto and Hiroyuki Ozoe, Transient three-dimensional numerical computation for silicon melt under a cusp-shaped magnetic field, 5th ASME/JSME Joint Thermal Eng. Conf, 1999.03.
345. Yoo Cheol Won, Koichi Kakimoto, Hiroyuki Ozoe, Transient three-dimensional numerical computation for unsteady oxygen concentration in a silicon melt during a Czochralski process under a cusp-shaped magnetic field, Journal of Crystal Growth, 10.1016/S0022-0248(01)01623-2, 233, 4, 622-630, 2001.12, [URL], This paper presents numerical computation for the transient oxygen concentration of a silicon melt in a Czochralski process under a cusp-shaped magnetic field. Transient three-dimensional numerical calculations were carried out for two cases of Ha = 0 and 161 for Pr = 0.013, Ra = 3.92 × 105, Recr=1329, Recu = -1596 and Sc = 5.5. The SIMPLE algorithm was employed. The oxygen concentration at a fixed point has a periodic oscillation as a function of time. The local and average oxygen concentrations in the silicon melt were less with a cusp-shaped magnetic field than those without a magnetic field. The power spectral density for the oxygen concentration fluctuation was also computed..
346. Yoo Cheol Won, Koichi Kakimoto, Hiroyuki Ozoe, Transient three-dimensional flow characteristics of Si melt in a Czochralski configuration under a cusp-shaped magnetic field, Numerical Heat Transfer; Part A: Applications, 36, 6, 551-561, 1999.11, Transient three-dimensional numerical computations were carried out for the convection of silicon melt in a Czochralski configuration under a cusp-shaped magnetic field. Numerical conditions are Ha = 0 and 161 with Pr = 0.013, Ra = 3.92×105, Recr = 1329, and Recu = -1596. Computed results show elliptic velocity and temperature profiles near the top of the melt that rotate in a circumferential direction of a crucible even under an axially symmetric cusp-shaped magnetic field at Ha = 161. Elliptic velocity and temperature distributions were stable but oscillating as a function of time. Velocity and temperature oscillation became a rather regular periodic structure under a cusp-shaped magnetic field in comparison with the nonmagnetic case..
347. Koichi Kakimoto, M. Eguchi, H. Ozoe, Use of an inhomogeneous magnetic field for silicon crystal growth, Journal of Crystal Growth, 10.1016/S0022-0248(97)00239-X, 180, 3-4, 442-449, 1997.01, [URL], The flow of liquid silicon and oxygen transfer during crystal growth under three different types of cusp-shaped magnetic field were clarified using numerical simulation, flow visualization, and infrared measurement of oxygen concentration in grown crystals. Velocity vectors obtained from numerical simulation are almost parallel to cusp-shaped magnetic fields since flow parallel to a magnetic field does not produce a Lorentz force. This parallel flow enhances homogenization of oxygen concentration along the radial direction in grown crystals. Cusp-shaped magnetic fields can control the flow velocity at the top of the melt. Since melt with a low concentration of oxygen at the top of the melt transfers directly from the free surface to the solid-liquid interface, a low concentration of oxygen in crystals can be achieved. Separation of fluid flow between the near surface and bulk can produce a spatial distribution of the concentration in the melt, and therefore a low oxygen concentration can be obtained in grown crystals..
348. Koichi Kakimoto, Kyung Woo Yi, Use of magnetic fields in crystal growth from semiconductor melts, Physica B: Condensed Matter, 10.1016/0921-4526(95)00529-3, 216, 3-4, 406-408, 1996.01, [URL], The three-dimensional pattern of a molten silicon flow under a magnetic field was revealed by X-ray radiography and large-scale three-dimensional numerical simulation. A flow visualization technique using X-ray radiography and a three-dimensional numerical simulation governed by a magneto-hydrodynamic equation revealed the pattern of the flow to be axisymmetric and under a low magnetic field, whereas the pattern becomes non-axisymmetric and three-dimensional under a high magnetic field even if an axisymmetric temperature boundary condition was applied. The result leads us to understand that the asymmetry originates in the intrinsic instability..
349. Hiroshi Yamada-kaneta, Terutaka Goto, Yasuhiro Saito, Yuichi Nemoto, Koji Sato, Koichi Kakimoto, Shintaro Nakamura, Vacancies in defect-free zone of point-defect-controlled CZ silicon observed by low -temperature ultrasonic measurements, Materials Science and Engineering B, Vol.134, 240-243., 2006.10.
350. Yoo Cheol Won, Koichi Kakimoto and Hiroyuki Ozoe, Visualization of the heat and mass transfer as well as the melt convection under a cusp-shaped magnetic field, The Eleventh Symposium on Chemical Engineering, Kyushu-Taejon/Chungnam, pp.327-328, 1998.10.
351. 柿本浩一,. Gao Bing, 中野智, 寒川義裕, 原田博文, “特集スクウェアタイプの太陽電池用Si結晶の作製総合報告高効率シリコン太陽電池の実現に向けて, 日本結品成長学会誌, 39, 3, 135(27)-141(33), Vol. 39, No. 3 (2012) 135(27)-141(33), 2012.10.
352. 牛王剛, 向井楠宏, 白石裕, 日比谷孟俊, 柿本浩一, 小山正人, シリコン融液の表面張力に及ぼす酸素分圧の影響, 日本結晶成長学会誌, Vol.23, No.5, 374-381, 1996.12.
353. 日比谷孟俊, 中村新, 柿本浩一, 今石宜之, 西澤伸一, 平田彰, 松井捷明, 横田孝夫, 依田真一, 中村富久, 足立聡, 鮫島浩人 , シリコンメルト液柱におけるマランゴニ対流の温度振動, 日本マイクログラピティ応用学会誌, Vol.13, No.2, 1996, 105(39)-109(43), 1996.03, [URL].
354. 牛正剛, 向井楠宏, 白石裕, 日比谷孟俊, 柿本浩一, 小山正人, シリコン融液の表面張力に及ぼす酸素と温度の影響, 日本結晶成長学会誌, Vol.24, No.4, 369-378, 1997.10.
355. 牛正剛, 向井楠宏, 白石裕, 日比谷孟俊, 柿本浩一, 小山正人, シリコン融液の表面張力に及ぼす酸素と温度の影響, Japanese Association for Crystal Growth (JACG), 1997.08.
356. 柿本浩一, 一方向性凝固法によるSi多結晶の育成と評価, 月刊「マテリアルインテグレーション」, 22, 12, 37-42, 2009.12.
357. 柿本浩一、野口真一郎、尾添紘之, 分子動力学法による半導体中の欠陥の拡散挙動解析, 日本機械学会熱工学講演会論文集, N0.01-9, 2001.11.
358. 柿本浩一,北嶋具教, 分子動力学法によるGaAs結晶中の空孔と格子間原子の拡散挙動, 結晶成長学会誌, Vol.29, No.2, p86, 2002.01.
359. 柿本浩一, 分子動力学法による溶融シリコンの輸送現象の理解, 熱物性, Vol.8, No.4, 220-225, 1994.10.
360. 平田学,柿本浩一,尾添紘之, 半導体溶液成長におけるゼーベック効果, 九州大学機能物質科学研究所報告, 第14巻,第2号,pp.149-155, 2000.12.
361. 柿本浩一、田代昭正、石井秀夫、篠崎高茂、橋本良夫, 半導体製造プロセスにおける電磁力の応用・マクロとナノスケール融合, 第15回計算機力学講演会講演論文集, No.02-02, pp743-744, 2002.01.
362. 日比谷孟俊, 中村新, 柿本浩一, 今石宜之, 西澤伸—, 平田彰, 向井楠宏, 松井捷明, 横田孝夫, 依田真一, 森田知二, 微小重力状態を利用した半導体シリコンメルトのマランゴニ対流の温度振動の精密測定とマランゴニ対流モード, Japanese Association for Crystal Growth (JACG), Vol.23, No.3, 139 (13)-139 (13), 1996.07.
363. 柿本浩一, 液体金属シリコンの対流不安定性, 日本物理学会誌, Vol.52, No.2, 90-96, 1997.02.
364. 柿本浩一、Gao Bing、中野 智、寒川義裕, 特集 どのように結晶成長現象をモデル化するか? 総合報告:半導体バルク結晶成長における熱と物質の輸送と成長速度との関係, 日本結晶成長学会誌, Vol.38, No.2, 86-92, 2011.07.
365. 寒川義裕、秋山 亨、伊藤智徳、白石賢二、柿本浩一, 特集 安定・準安定:閃亜鉛鉱構造とウルツ鉱構造 総合報告「立方晶GaNの成長過程と構造安定性」, 日本結晶成長学会誌, Vol.34, No.4, (2008) 213-217., 2008.01.
366. 寒川 義裕, 草場彰, 白石賢二, 柿本 浩一, 纐纈明伯, 窒化物半導体 MOVPE の熱力学解析: 面方位依存性 (特集 エピタキシーの基礎: ステップダイナミクスと熱力学的考察), 日本結晶成長学会誌, 43, (4), 233-238, 2017.01.
367. 柿本浩一,梅原猛,尾添紘之, 等圧下におけるシリコン中の点欠陥の輸送現象, 九州大学機能物質科学研究所報告, 第13巻,第2号,pp.87-91, 1999.11.
368. 柿本浩一,末永英俊,尾添紘之, 等温等圧下におけるシリコンの物性のシミュレーション, 九州大学機能物質科学研究所報告, 第12巻第1号,pp.7-10, 1998.07.
369. 柿本 浩一、篠崎 高茂、田代 昭正、石井 秀夫, 電磁攪拌によるシリコン結晶育成時の融液流動解析, 第52回理論応用力学講演会講演論文集, pp523-524, 2003.01.
370. 北嶋具教、柿本浩一、北村健二, 2重坩堝ACRT法におけるLiNbO3融液の対流解析, 第47回人工結晶討論会講演要旨集, pp97-98, 2002.01.
371. 北嶋具教、柿本浩一, 2重坩堝法を用いたニオブ酸リチウム(LiNbO3)の融液対流解析, 日本結晶成長学会誌, Vol.29 No.2, 2002.01.
372. 柿本浩一、王育人, X線回折によるシリコン融解凝固過程のその場観察, 第47回人工結晶討論会講演要旨集, pp60-70, 2002.01.

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