| 1. |
Qing Wang, Yongpeng Tang, Asuka Miura, Koji Miyazaki, Zenji Horita, Satoshi Iikubo, Improving thermoelectric properties of Bi2Te3 by straining under high
pressure: Experiment and DFT calculation, Scripta Materialia, 243, 115991, 2024.01.  |
| 2. |
Shota Hayakawa, Toshiharu Chono, Kosuke Watanabe, Shoya Kawano, Kazuma Nakamura, Koji Miyazaki, Ab initio calculation for electronic structure and optical property of tungsten carbide in a TiCN-based cermet for solar thermal applications, Scientific Reports, 13, 9407, 2023.06. |
| 3. |
D. Liu , H. Li, Y. Li, T. Toyoda, K. Miyazaki, S. Hayase, C. Ding, Q. Shen, Simultaneous Characterization of Optical, Electronic, and Thermal Properties of Perovskite Single Crystals Using a Photoacoustic Technique, ACS Photonics, 10, 265-273, 2023.01. |
| 4. |
Y. Amma, K. Miura, S. Nagata, T. Nishi, S. Miyake, K. Miyazaki, M. Takashiri, Ultra-long air-stability of n-type carbon nanotube films with low thermal conductivity and all-carbon thermoelectric generators, Scientific Reports, 12, 21603, 2022.12. |
| 5. |
Shota Yajima, Nanako Io, Koji Miyazaki, Tomohide Yabuki, Heat flux partitioning and macrolayer observation in pool boiling of water on a surface with artificial nucleation sites, International Journal of Heat and Mass Transfer, 194, 122924, 2022.09. |
| 6. |
Ajay Kumar Baranwal, Shrikant Saini, Yoshitaka Sanehira, Gaurav Kapil, Muhammad Akmal Kamarudin, Chao Ding, Shahrir Razey Sahamir, Tomohide Yabuki, Satoshi Iikubo, Qing Shen, Koji Miyazaki, Shuzi Hayase, Unveiling the role of metal oxide/Sn perovskite interface leading to low efficiency of Sn-perovskite solar cells but providing high thermoelectric properties, ACS Applied Energy Materials , https://doi.org/10.1021/acsaem.2c01437, 5, 8, 9750-9758, 2022.08. |
| 7. |
Ryo Abe, Yuki Sekimoto, Shirkant Saini, Koji Miyazaki, Qinyi Li, Dawei Li, Koji Takahashi, Takashi Yagi, Masakazu Nakamura, Round Robin Study on the Thermal Conductivity/Diffusivity of a Gold Wire with a Diameter of 30 μm Tested via Five Measurement Methods, Journal of Thermal Science, 31, 1037-1051, 2022.05. |
| 8. |
Ajay Kumar Baranwal, Kohei Nishimura, Dong Liu, Muhammad Akmal Kamarudin, Gaurav Kapil, Shrikant Saini, Tomohide Yabuki, Satoshi Iikubo, Takashi Minemoto, Kenji Yoshino, Koji Miyazaki, Qing Shen, Shuzi Hayase, Relationship between Carrier Density and Precursor Solution Stirring for Lead-Free Tin Halide Perovskite Solar Cells Performance, ACS Applied Energy Materials, 5, 4, 4002-4007, 2022.04. |
| 9. |
Masayuki Morimoto, Shoya Kawano, Shotaro Miyamoto, Koji Miyazaki, Shuzi Hayase, Satoshi Iikubo, Electronic structure and thermal conductance of the MASnI3/Bi2Te3 interface: a first-principles study, Scientific Report, 12, 217, 2022.01. |
| 10. |
Oga Norimasa, Masataka Hase, Ryotaro Mori, Mai Hayamizu, Hiroshi Murotani, Koji Miyazaki, Masayuki Takashiri, Determination of group velocity based on nanoindentation using Si and SiO2 /Si wafers, AIP Advances, https://doi.org/10.1063/5.0055581, 11, 075216, 2021.07. |
| 11. |
Yihang Jiao, Koji Miyazaki, Tomohide Yabuki, Measurement of thermal boundary resistance between water and superhydrophobic surfaces by the bi-directional differential 3ω method, International Communications in Heat and Mass Transfer, https://doi.org/10.1016/j.icheatmasstransfer.2021.105404, 126, 105404, 2021.07. |
| 12. |
Shiying Liu, Guojian Li, Mingdi Lan, Miaoyong Zhu, Koji Miyazaki, Qiang Wang, Role of intrinsic defects on thermoelectric properties of ZnO:Al films, Ceramics International, https://doi.org/10.1016/j.ceramint.2021.03.098, 47, 12, 17760-17767, 2021.06. |
| 13. |
Rauf Khan, Michitaka Ohtaki, Satoshi Hata, Koji Miyazaki, Reiji Hattori, Thermal conductivity of nano-crystallized indium-gallium-zinc oxide thin films determined by differential three-omega method, Nanomaterials, 11, 6, 1547, 2021.06. |
| 14. |
Takanori Tanaka, Koji Miyazaki, Tomohide Yabuki, Observation of heat transfer mechanisms in saturated pool boiling of water by high-speed infrared thermometry, International Journal of Heat and Mass Transfer, https://doi.org/10.1016/j.ijheatmasstransfer.2021.121006, 170, 121006, 2021.05. |
| 15. |
Masanori Morisaki, Shota Minami, Koji Miyazaki, Tomohide Yabuki, Direct local heat flux measurement during water flow boiling in a rectangular minichannel using a MEMS heat flux sensor, Experimental Thermal and Fluid Science, https://doi.org/10.1016/j.expthermflusci.2020.110285, 121, 110285, 2021.02. |
| 16. |
Masayuki Morimoto, Shoya Kawano, Koji Miyazaki, Satoshi Iikubo, Structural stability and electronic property evaluations for different Bi2Te3 (0 0 1) termination surfaces, Applied Surface Science, https://doi.org/10.1016/j.apsusc.2020.146454, 525, 146454, 2020.09. |
| 17. |
Takanori Tanaka, Koji Miyazaki, Tomohide Yabuki, Electrolytic Bubble Nucleation Activation in Pool Boiling of Water: Heat Transfer Enhancement and Reduction of Incipient Boiling Superheat, International Journal of Heat and Mass Transfer, https://doi.org/10.1016/j.ijheatmasstransfer.2020.119755, 157, 119755, 2020.08. |
| 18. |
Shirikant Saini, Ajay Kumar Baranwal, Tomohide Yabuki, Shuzi Hayase, Koji MIyazaki, Uni-leg thermoelectric module comprised by coated hybridperovskite thin film, Journal of Heat Transfer, https://doi.org/10.1115/1.4047360, 142, 7, 074502, 2020.07. |
| 19. |
Mohamed Atwa, 中川鉄水, 與那嶺亮, David C. Lloyd, Makoto Schreiber, 宮崎 康次, 竹内恒博, 岡田佳憲, Top-down approach using supercritical carbon dioxide ball milling for producing sub-10 nm Bi2Te3 grains, Applied Physics Express, 10.35848/1882-0786/ab91d2, 13, 6, 067002-1-067002-5, 2020.05. |
| 20. |
S. Liu, G. Li, M. Lan, Y. Piao, K. Miyazaki and Q. Wang, Effect of growth modes on electrical and thermal transport of thermoelectric ZnO:Al films, Acta. Crystal B: Structural Science, Crystal Engineering and Materials, https://doi.org/10.1107/S2052520620002383, 76, 259-266, 2020.04. |
| 21. |
Shirikant Saini, Ajay Kumar Baranwal, Tomohide Yabuki, Shuzi Hayase, Koji Miyazaki, Hybrid-Halide Perovskite Thin Film Growth for Thermoelectric Applications, Journal of Electronic Materials, 10.1007/s11664-020-07958-6, 2020.01. |
| 22. |
Ajay Kumar Baranwal, Shirikant Saini, Zhen Wang, Kengo Hamada, Daisuke Hirotani, Kohei Nishimura, Muhammad Akmal Kamarudin, Gaurav Kapil, Tomohide Yabuki, Satoshi Iikubo, Qing Shen, Koji Miyazaki, Shuzi Hayase, Effect of Precursor Solution Aging on the Thermoelectric Performance of CsSnI3 Thin Film, Journal of Electronic Materials, 10.1007/s11664-019-07846-8, 49, 5, 2698-2703, 2019.12, ICT2019発表特集号. |
| 23. |
Yanqiong Zheng, Jie Tang, Weiguang Li, Junle yu, Bin Wei, Xifeng Li, Jifeng Shi, Koji Miyazaki, Control of the pore size of honeycomb polymer film from micrometers to nanometers via substrate-temperature regulation and its application to photovoltaic and heat-resistant polymer films, Nanotechnology, 10.1088/1361-6528/ab4521, 31, 015301, 2019.10. |
| 24. |
Ajay Kumar Baranwal, Shirikant Saini, Zhen Wang, Daisuke Hirotani, Tomohide Yabuki, Satoshi Iikubo, Koji Miyazaki, Shuzi Hayase, Interface engineering using Y2O3 scaffold to enhance the thermoelectric performance of CsSnI3 thin film, Organic Electronics, 10.1016/j.orgel.2019.105488, 76, 105488, 2019.10. |
| 25. |
Shirikant Saini, Paolo Mele, Takafumi Oyake, Junichiro Shiomi, Janne-Petteri Niemel, Maarit Kappinen, Koji Miyazaki, Chaoyang Li, Toshiyuki Kawaharamura, Ataru Ichinose, Leopoldo Molina-Luna, Porosity-tuned thermal conductivity in thermoelectric Al-doped ZnO thin films grown by mist-chemical vapor deposition, Thin Solid Films, 10.1016/j.tsf.2019.06.010, 685, 180-185, 2019.09. |
| 26. |
Laurent Tranchant, Satoki Hamamura, Jose Ordonez-Miranda, Tomohide Yabuki, Alejandro Vega-Flick, Fernando Cervantes-Alvarez, Juan Jose, Alvarado-Gil, Sebastian Volz, Koji Miyazaki, Two-Dimensional Phonon Polariton Heat Transport, Nano Letters, 10.1021/acs.nanolett.9b02214, 19, 10, 6924-6930, 2019.09, 大学よりプレスリリース. |
| 27. |
Shirikant Saini, Ajay Kumar Baranwal, Tomohide Yabuki, Shuzi Hayase, Koji Miyazaki, Growth of halide perovskites thin films for thermoelectric applications, MRS Advances, 10.1557/adv.2019.279, 2019.06. |
| 28. |
Measurement of Thermal Boundary Resistance of Organic-Inorganic Materials. |
| 29. |
Koji Miyazaki, Kou Kuriyama, Tomohide Yabuki, Printed Thermoelectric Device, Proceedings of PowerMEMS2018, 2018.12. |
| 30. |
Laurent Tranchant, Satoki Hamamura, Jose Ordonez-Miranda, Sebastian Volz, Koji Miyazaki, Experimental study of the in-plane thermal conductivity enhancement of suspended glass thin films due to long range surface phonon-polaritons, Proceedings of the 16th international heat transfer conference, IHTC16-23810, 2018.08. |
| 31. |
Koji Miyazaki, Kou Kuriyama Tomohide Yabuki, Interfacial thermal resistance between Bismuth Telluride and PEDOT:PSS, Proceedings of 37th International and 16th European Conference on Thermoelectrics, 266, 2018.07. |
| 32. |
Koji Miyazaki, Printed Flexible Thermoelectric Device of the Organic/Inorganic composite, Proceedings of ICOT2018, 2018.02, ICOT
International Conference on Organic and Hybrid Thermoelectrics. |
| 33. |
Tsubasa Matuso, Tomohide Yabuki, Laurent Tranchant, Koji Miyazaki, Normal Emittance of Metal Coated Silica Spheres Array, Proceedings of the Ninth JSME-KSME Thermal and Fluids Engineering Conferece, 2017.10. |
| 34. |
Laurent Tranchant, Jose Ordonez-Miranda, Sebastian Volz, Koji Miyazaki, Experimental Investigation of the Enhanced Thermal Conductivity of Silica Suspended Thin Films due to Long-Range Surface Phonon-Polaritons, Proceedings of Nanorad2017, 2017.06. |
| 35. |
Shota Hama, Kou Kuriyama, Laurent Tranchant, Tomohide Yabuki, Koji Miyazaki, In-plane Thermal Conductivity of Bismuth Telluride Thin Films, Proceedings of Asian Conference on Thermal Sciences 2017, 2017.03. |
| 36. |
P. Mele, S. Saini, A. Tiwari, P. E. Hopkins, K. Miyazaki, A. Ichinose, J. Niemela, M. Karppinen, Thermoelectric and Structural Characterization of Al-Doped ZnO/Y2O3 Multilayers, JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY, 10.1166/jnn.2017.13717, 17, 3, 1616-1621, 2017.03, The influence of Y2O3 nanolayers on thermoelectric performance and structure of 2% Al-doped ZnO (AZO) thin films has been studied. Multilayers based on five 50 nm thick AZO layers alternated with few nanometers thick Y2O3 layers were prepared by pulsed laser deposition on Al2O3 single crystals by alternate ablation of AZO target and Y2O3 target. The number of laser shots on Y2O3 target was maintained very low (5, 10 and 15 pulses in three separate experiments. The main phase (AZO) presents polycrystalline orientation and typical columnar growth not affected by the presence of Y2O3 nanolayers. The multilayer with 15 laser shots of Y2O3 showed best thermoelectric performance with electrical conductivity sigma = 48 S/cm and Seebeck coefficient S=-82 mu V/K, which estimate power factor (S-2.sigma) about 0.03 x 10(-3) W m(-1) K-2 at 600 K. The value of thermal conductivity (kappa) was found 10.03 W m(-1) K-1 at 300 K, which is one third of typical value previously reported for bulk AZO. The figure of merit, ZT = S-2 .sigma . T/kappa, is calculated 9.6 x 10(-4) at 600 K. These results demonstrated the feasibility of nanoengineered defects insertion for the depression of thermal conductivity.. |
| 37. |
Laurent Tranchant, JoseOrdonez-Miranda,Taihei Matsumoto, Sebastian Volz, Koji Miyazaki, Experimental Detection of Enhanced Thermal Properties of Glass Thin Films due to Long Range Surface Phonon-Polaritons, Proceedings of the 4th International Forum on Heat Transfer, 1966, 2016.11, Tranchant助教主担当. |
| 38. |
Takanori Tanaka, Tomohide Yabuki, Koji Miyazaki, Pool Boiling CHF Enhanced with Superhydrophilic Micro/Nano Structures Fabricated by Thermal Spray and Chemical Oxidation, Proceedings of the 4th International Forum on Heat Transfer, 1991, 2016.11, 矢吹助教主担当. |
| 39. |
Zhuoya Zheng, Tomohide Yabuki, Laurent Tranchant, Atsushi Sakurai, Koji Miyazaki, Thermal Radiation of Spectrally Selective Solar Absorber Based on MOD Method, Proceedings of the 4th International Forum on Heat Transfer, 1937, 2016.11. |
| 40. |
Laurent Tranchant, Jose Ordonez-Miranda, Taihei Matsumoto, Sebastian Volz, Koji Miyazaki, Experimental detection of the enhanced longitudinal propagation of surface phonon-polaritons on SiO2 thin films, Proceedings of the 11th Asian Thermophysical Properties Conference, 2016.10. |
| 41. |
S. Ikeuchi, K. Shimada, S. Tanaka, T. Yabuki, K. Miyazaki, 2 omega and 3 omega thermal conductivity measurements for thin dielectric films, Proceedings of the 27th International Symposium on Transport Phenomena, 2016.09. |
| 42. |
Yuta Kage, Harutoshi Hagino, Ryoto Yanagisawa, Jeremie Maire, Koji Miyazaki, Masahiro Nomura, Thermal phonon transport in Si thin film with dog-leg shaped asymmetric nanostructures, JAPANESE JOURNAL OF APPLIED PHYSICS, 10.7567/JJAP.55.085201, 55, 8, 085201, 2016.08, Thermal phonon transport in single-crystalline Si thin films with dog-leg shaped nanostructures was investigated. Thermal conductivities for the forward and backward directions were measured and compared at 5 and 295K by micro thermoreflectance. The Si thin film with dog-leg shaped nanostructures showed lower thermal conductivities than those of nanowires and two-dimensional phononic crystals with circular holes at the same surface-to-volume ratio. However, asymmetric thermal conductivity was not observed at small temperature gradient condition in spite of the highly asymmetric shape though the size of the pattern is within thermal phonon mean free path range. We conclude that strong temperature dependent thermal conductivity is required to observe the asymmetric thermal phonon conduction in monolithic materials with asymmetric nanostructures. (C) 2016 The Japan Society of Applied Physics. |
| 43. |
Yoshiyuki Nonoguchi, Motohiro Nakano, Tomoko Murayama, Harutoshi Hagino, Shota Hama, Koji Miyazaki, Ryosuke Matsubara, Masakazu Nakamura, Tsuyoshi Kawai, Simple Salt-Coordinated n-Type Nanocarbon Materials Stable in Air, ADVANCED FUNCTIONAL MATERIALS, 10.1002/adfm.201600179, 26, 18, 3021-3028, 2016.05, After more than three decades of molecular and carbon-based electronics, the creation of air-and thermally stable n-type materials remains a challenge in the development of future p/n junction devices such as solar cells and thermoelectric modules. Here a series of ordinary salts are reported such as sodium chloride (NaCl), sodium hydroxide (NaOH), and potassium hydroxide (KOH) with crown ethers as new doping reagents for converting single-walled carbon nanotubes to stable n-type materials. Thermoelectric analyses reveal that these new n-type single-walled carbon nanotubes display remarkable air stability even at 100 degrees C for more than 1 month. Their thermoelectric properties with a dimensionless fi gure-of-merit (ZT) of 0.1 make these new n-type single-walled carbon nanotubes a most promising candidate for future n-type carbon-based thermoelectric materials.. |
| 44. |
S. Saini, P. Mele, H. Honda, T. Suzuki, K. Matsumoto, K. Miyazaki, A. Ichinose, L. Molina Luna, R. Carlini, A. Tiwari, Effect of self-grown seed layer on thermoelectric properties of ZnO thin films, THIN SOLID FILMS, 10.1016/j.tsf.2015.09.060, 605, 289-294, 2016.04, The influence of self-grown seed has been studied on thermoelectric performance of 2% Al-doped ZnO(AZO) thin films. The thickness and orientation of c-axis domains in seed layer change on different substrates while other deposition conditions were kept unchanged for a comparable study. The changes occur because of the different nucleation process of thin film growth on substrate interface and the different lattice mismatch between AZO and substrate. Thin films are grown by pulsed laser deposition on single crystals (SrTiO3 (STO) and Al2O3) and cheap amorphous fused silica (FS) substrates at 400 degrees C. All thin films are c-axis oriented. The grains are highly connected and elongated in shape which leads to high thermoelectric properties. The thicker self-grown seed layer is found in thin film deposited on FS substrates which shows best performance: electrical conductivity sigma = 93 S/cm and Seebeck coefficient S = -203 mu V/K, which estimate power factor (S-2.sigma) about 0.37 x 10(-3) Wm(-1)K(-2) at 600 K. The value of thermal conductivity (kappa) was found lowest (4.89 Wm(-1)K(-1)) for thin film deposited on FS than the other thin films (6.9 Wm(-1)K(-1) on Al2O3 and 6.55 Wm(-1)K(-1) on STO) at 300 K. The figure of merit, ZT = S-2.sigma.T/kappa, is calculated 0.046 at 600 K, 5 times larger than the ZT of our previous reported bulk AZO, which is promising for practical applications of thermoelectric oxide thin films. (C) 2015 Elsevier B.V. All rights reserved.. |
| 45. |
S. Saini, P. Mele, K. Miyazaki, A. Tiwari, On-chip thermoelectric module comprised of oxide thin film legs, ENERGY CONVERSION AND MANAGEMENT, 10.1016/j.enconman.2016.02.001, 114, 251-257, 2016.04, On-chip thermoelectric thin film modules containing 5 legs of n-type (Al0.02Zn0.98O) and 5 legs of p-type (Ca3Co4O9) were fabricated on Al2O3, SrTiO3 single crystal, and fused silica substrates by pulsed laser deposition technique. Performance of modules was evaluated using ad hoc customized system where the module was set vertically for temperature gradient. The maximum output power (P-max) was obtained on Al2O3 (0001) single crystal substrate with temperature difference (Delta T) = 230 degrees C (T-h = 300 degrees C): P-max = 29.9 pW. The value of maximum output power increases with increase of temperature difference (Delta T) These results are encouraging for the practical applications of thermoelectric oxide thin films. (C) 2016 Elsevier Ltd. All rights reserved.. |
| 46. |
Koji Miyazaki, Enhanced Figure of Merit of a Self-assembled Micro-porous Bismuth Telluride Thin Films, Proceedings of the First Pacific Rim Thermal Engineering Conference, PRTEC-1KL17, 2016.03. |
| 47. |
Harutoshi Hagino, Saburo Tanaka, Naoki Tanimura, Koji Miyazaki, Thermal and Electrical Conductivities of Porous Si Membranes, INTERNATIONAL JOURNAL OF THERMOPHYSICS, 10.1007/s10765-014-1643-z, 36, 10-11, 2548-2564, 2015.11, The microstructure of materials affects thermal and electrical transport as well as the physical properties. The effects of the microstructure on both thermal and electrical transport in silicon membranes with periodic microporous structures produced from silicon-on-insulator wafers using microfabrication processes were studied. The in-plane thermal and electrical conductivities of the Si membranes were measured simultaneously by using a self-heating method. The measured thermal conductivity was compared with the result from the periodically laser-heating method. The thermal and electrical conductivities were much lower in the porous membranes than in the non-porous membrane. The measured thermal conductivity was much lower than expected based on values determined using classical models. A significant phonon size effect was observed even in microsized structures, and the mean free path for phonons was very long. It was concluded that phonon transport is quasi-ballistic and electron transport is diffuse in microporous Si structures. It was suggested that the microstructure had a different effect on thermal and electrical transport.. |
| 48. |
Masayuki Takashiri, Kensuke Kurita, Harutoshi Hagino, Saburo Tanaka, Koji Miyazaki, Enhanced thermoelectric properties of phase-separating bismuth selenium telluride thin films via a two-step method, JOURNAL OF APPLIED PHYSICS, 10.1063/1.4928311, 118, 6, 065301, 2015.08, A two-step method that combines homogeneous electron beam (EB) irradiation and thermal annealing has been developed to enhance the thermoelectric properties of nanocrystalline bismuth selenium telluride thin films. The thin films, prepared using a flash evaporation method, were treated with EB irradiation in a N-2 atmosphere at room temperature and an acceleration voltage of 0.17 MeV. Thermal annealing was performed under Ar/H-2 (5%) at 300 degrees C for 60 min. X-ray diffraction was used to determine that compositional phase separation between bismuth telluride and bismuth selenium telluride developed in the thin films exposed to higher EB doses and thermal annealing. We propose that the phase separation was induced by fluctuations in the distribution of selenium atoms after EB irradiation, followed by the migration of selenium atoms to more stable sites during thermal annealing. As a result, thin film crystallinity improved and mobility was significantly enhanced. This indicates that the phase separation resulting from the two-step method enhanced, rather than disturbed, the electron transport. Both the electrical conductivity and the Seebeck coefficient were improved following the two-step method. Consequently, the power factor of thin films that underwent the two-step method was enhanced to 20 times (from 0.96 to 21.0 mu W/(cmK(2)) that of the thin films treated with EB irradiation alone. (C) 2015 AIP Publishing LLC.. |
| 49. |
S. Kudo, H. Hagino, S. Tanaka, K. Miyazaki, M. Takashiri, Determining the Thermal Conductivity of Nanocrystalline Bismuth Telluride Thin Films Using the Differential 3 omega Method While Accounting for Thermal Contact Resistance, JOURNAL OF ELECTRONIC MATERIALS, 10.1007/s11664-015-3646-3, 44, 6, 2021-2025, 2015.06, We have estimated the thermal conductivity of nanocrystalline bismuth telluride thin films using the differential 3 omega method, taking into account the thermal contact resistance (TCR) between the substrate and thin-film layers. The thin films were prepared on alumina substrates by radio-frequency (RF) magnetron sputtering at temperature of 200A degrees C. Film thickness varied between 0.8 mu m and 3.1 mu m. The structural properties of the films were analyzed using x-ray diffraction analysis. Their electrical conductivity, Seebeck coefficient, and power factor were evaluated. For measurement of thermal properties by the differential 3 omega method, SiO2 thin films were deposited onto the samples, to act as insulating layers. Thin aluminum wire was then patterned onto the SiO2 layer. The observed variations in temperature amplitude as a function of film thickness indicated that the TCR contribution was very small and could therefore be neglected when estimating the thermal conductivity of the thin films. The thermal conductivity of the nanocrystalline bismuth telluride thin films with thickness of 0.8 mu m and 2.1 mu m were determined to be 0.55 W/(m K) and 0.48 W/(m K), respectively.. |
| 50. |
D. Zheng, S. Tanaka, K. Miyazaki, M. Takashiri, Evaluation of Specific Heat, Sound Velocity and Lattice Thermal Conductivity of Strained Nanocrystalline Bismuth Antimony Telluride Thin Films, JOURNAL OF ELECTRONIC MATERIALS, 10.1007/s11664-014-3518-2, 44, 6, 1679-1687, 2015.06, To investigate the effect of strain on specific heat, sound velocity and lattice thermal conductivity of nanocrystalline bismuth antimony telluride thin films, we performed both experimental study and modeling. The nanocrystalline thin films had mostly preferred crystal orientation along c-axis, and strains in the both directions of c-axis and a-b-axis. It was found that the thermal conductivity of nanocrystalline thin films decreased greatly as compared with that of bulk alloys. To gain insight into the thermal transport in the strained nanocrystalline thin films, we estimated the lattice thermal conductivity based on the phonon transport model of full distribution of mean free paths accounting for the effects of grain size and strain which was influenced to both the sound velocity and the specific heat. As a result, the lattice thermal conductivity was increased when the strain was shifted from compressive to tensile direction. We also confirmed that the strain was influenced by the lattice thermal conductivity but the reduction of the lattice thermal conductivity of thin films can be mainly attributed to the nano-size effect rather than the strain effect. Finally, it was found that the measured lattice thermal conductivities were in good agreement with modeling.. |
| 51. |
S. Saini, P. Mele, H. Honda, K. Matsumoto, K. Miyazaki, L. Molina Luna, P. E. Hopkins, Influence of Postdeposition Cooling Atmosphere on Thermoelectric Properties of 2% Al-Doped ZnO Thin Films Grown by Pulsed Laser Deposition, JOURNAL OF ELECTRONIC MATERIALS, 10.1007/s11664-014-3471-0, 44, 6, 1547-1553, 2015.06, We have investigated the thermoelectric properties of 2% Al-doped ZnO (AZO) thin films depending on the postdeposition cooling atmosphere [in oxygen pressure (AZO-O) or vacuum (AZO-V)]. Thin films were grown by pulsed laser deposition on sapphire () substrates at various deposition temperatures ( to ). All films were c-axis oriented. The electrical conductivity of AZO-V thin films was higher than that of AZO-O thin films across the whole temperature range from 300 K to 600 K, due to the optimal carrier concentration () of AZO-V samples. Furthermore, the thermoelectric performance of AZO-V films increased with the deposition temperature; for instance, the highest power factor of and dimensionless figure of merit of 0.07 at 600 K were found for AZO-V thin film deposited at .. |
| 52. |
K. Kusagaya, H. Hagino, S. Tanaka, K. Miyazaki, M. Takashiri, Structural and Thermoelectric Properties of Nanocrystalline Bismuth Telluride Thin Films Under Compressive and Tensile Strain, JOURNAL OF ELECTRONIC MATERIALS, 10.1007/s11664-014-3496-4, 44, 6, 1632-1636, 2015.06, To investigate the effect of strain on bismuth telluride films, we applied different compressive and tensile strains to thin films by changing the bending radius of a flexible substrate so the strain ranged from -0.3% (compressive) to +0.3% (tensile). The structural properties of the strained thin films, composed of nanosized grains, were analyzed by x-ray diffraction and scanning electron microscopy. For all samples the main peak was the (015) diffraction peak; crystal orientation along the (015) growth direction was slightly enhanced by application of compressive strain. The thermoelectric properties of strained bismuth telluride thin films were evaluated by measurement of electrical conductivity, Seebeck coefficient, and power factor. The magnitude and direction of the applied strain did not significantly affect the power factor, because when the strain changed from compressive to tensile the electrical conductivity increased and the absolute Seebeck coefficient decreased.. |
| 53. |
Kunihisa Kato, Tsuyoshi Muto, Takeshi Kondo, Koji Miyazaki, Fabrication of flexible thermoelectric thin film module using micro porous structure, IEEE CPMT Symposium Japan 2014 - The Leading International Components, Packaging, and Manufacturing Technology Symposium: "Packaging for Future Optoelectronics, RF/High-Speed Electronics and Bioelectronics", ICSJ 2014, 10.1109/ICSJ.2014.7009640, 182-185, 2015.01, We investigated effects of the submicron structured thermoelectric thin films and module on their performance. The output power of the submicron structured module was 1.5 times greater than that of a smooth structured module.. |
| 54. |
Masayuki Takashiri, Kazuo Imai, Masato Uyama, Harutoshi Hagino, Saburo Tanaka, Koji Miyazaki, Yoshitake Nishi, Effects of homogeneous irradiation of electron beam on crystal growth and thermoelectric properties of nanocrystalline bismuth selenium telluride thin films, JOURNAL OF ALLOYS AND COMPOUNDS, 10.1016/j.jallcom.2014.05.146, 612, 98-102, 2014.11, The effects of homogeneous irradiation of electron beam (EB) on the crystal growth and thermoelectric properties of nanocrystalline bismuth selenium telluride thin films were investigated. The thin films were prepared using a flash evaporation method, after which EB irradiation was performed under N-2 at room temperature at an accelerated voltage of 0.17 MeV. SEM revealed that the untreated thin film was composed of a large quantity of rice-like nanostructures. With increasing the EB irradiation dose, a number of nanodots with diameters of less than 10 nm became visible on the surface of the rice-like nanostructures. The crystallinity and the crystal orientation were enhanced with increasing EB irradiation dose while the average crystal grain size remained almost the same size as that of the untreated thin film. In terms of thermoelectric properties, the mobility of the thin films was enhanced as the EB irradiation dose was increased while the carrier concentration was not greatly changed. As a result, both the electrical conductivity and the Seebeck coefficient were improved with increasing EB irradiation dose. Consequently, even though there is still room for further improvement, the power factor was enhanced around sevenfold (from 0.14 to 0.96 mu W/cm/K-2) by the EB irradiation treatment. (C) 2014 Elsevier B.V. All rights reserved.. |
| 55. |
Kimito Ishihara, Makoto Kashiwagi, Tubasa Matsuo, Minoru Iwata, Koji Miyazaki, Enhanced Emittance of a Silica Photonic Crystal, ISTP-25, 2014.11. |
| 56. |
Harutoshi Hagino, Koji Miyazaki, Thermal Rectifier by Using Semi-ballistic Transfer of Phonons in Asymmetric Liner Structures, ISTP-25, 2014.11. |
| 57. |
Masayuki Takashiri, Saburo Tanaka, Harutoshi Hagino, Koji Miyazaki, Strain and grain size effects on thermal transport in highly-oriented nanocrystalline bismuth antimony telluride thin films, INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, 10.1016/j.ijheatmasstransfer.2014.04.048, 76, 376-384, 2014.09, We investigated the effects of strain and grain size on the thermal transport of highly-oriented nanocrystalline bismuth antimony telluride thin films using both experimental studies and modeling. The fabricated thin films had preferred crystal orientation along the c-axis, average grain sizes of 30 |
| 58. |
Masayuki Takashiri, Kazuo Imai, Masato Uyama, Harutoshi Hagino, Saburo Tanaka, Koji Miyazaki, Yoshitake Nishi, Comparison of crystal growth and thermoelectric properties of n-type Bi-Se-Te and p-type Bi-Sb-Te nanocrystalline thin films: Effects of homogeneous irradiation with an electron beam, JOURNAL OF APPLIED PHYSICS, 10.1063/1.4881676, 115, 21, 214311, 2014.06, The effects of homogenous electron beam (EB) irradiation on the crystal growth and thermoelectric properties of n-type Bi-Se-Te and p-type Bi-Sb-Te thin films were investigated. Both types of thin films were prepared by flash evaporation, after which homogeneous EB irradiation was performed at an acceleration voltage of 0.17MeV. For the n-type thin films, nanodots with a diameter of less than 10nm were observed on the surface of rice-like nanostructures, and crystallization and crystal orientation were improved by EB irradiation. The resulting enhancement of mobility led to increased electrical conductivity and thermoelectric power factor for the n-type thin films. In contrast, the crystallization and crystal orientation of the p-type thin films were not influenced by EB irradiation. The carrier concentration increased and mobility decreased with increased EB irradiation dose, possibly because of the generation of defects. As a result, the thermoelectric power factor of p-type thin films was not improved by EB irradiation. The different crystallization behavior of the n-type and p-type thin films is attributed to atomic rearrangement during EB irradiation. Selenium in the n-type thin films is more likely to undergo atomic rearrangement than the other atoms present, so only the crystallinity of the n-type Bi-Se-Te thin films was enhanced. (C) 2014 AIP Publishing LLC.. |
| 59. |
M. Takashiri, S. Tanaka, K. Miyazaki, Determination of the Origin of Crystal Orientation for Nanocrystalline Bismuth Telluride-Based Thin Films Prepared by Use of the Flash Evaporation Method, JOURNAL OF ELECTRONIC MATERIALS, 10.1007/s11664-013-2896-1, 43, 6, 1881-1889, 2014.06, We have investigated the origin of crystal orientation for nanocrystalline bismuth telluride-based thin films. Thin films of p-type bismuth telluride antimony (Bi-Te-Sb) and n-type bismuth telluride selenide (Bi-Te-Se) were fabricated by a flash evaporation method, with exactly the same deposition conditions except for the elemental composition of the starting powders. For p-type Bi-Te-Sb thin films the main x-ray diffraction (XRD) peaks were from the c-axis (I {00l} pound/I {hkl} pound = 0.88) whereas n-type Bi-Te-Se thin films were randomly oriented (I {00l} pound/I {hkl} pound = 0.40). Crystal orientation, crystallinity, and crystallite size were improved for both types of thin film by sintering. For p-type Bi-Te-Sb thin films, especially, high-quality structures were obtained compared with those of n-type Bi-Te-Se thin films. We also estimated the thermoelectric properties of the as-grown and sintered thin films. The power factor was enhanced by sintering; maximum values were 34.9 mu W/cm K-2 for p-type Bi-Te-Sb thin films at a sintering temperature of 300A degrees C and 23.9 mu W/cm K-2 for n-type Bi-Te-Se thin films at a sintering temperature of 350A degrees C. The exact mechanisms of film growth are not yet clear but we deduce the crystal orientation originates from the size of nano-clusters generated on the tungsten boat during flash evaporation.. |
| 60. |
Shrikant Saini, Paolo Mele, Hiroaki Honda, Dave J. Henry, Patrick E. Hopkins, Leopoldo Molina-Luna, Kaname Matsumoto, Koji Miyazaki, Ataru Ichinose, Enhanced thermoelectric performance of Al-doped ZnO thin films on amorphous substrate, JAPANESE JOURNAL OF APPLIED PHYSICS, 10.7567/JJAP.53.060306, 53, 6, 060306-1-060306-4, 2014.06, 2% Al-doped ZnO (AZO) thin films fabricated at 300 C by pulsed laser deposition (PLD) on amorphous fused silica demonstrated the high quality crystallinity and grain connection, which correlates to the high thermoelectric performance: electrical conductivity sigma = 923S/cm and Seebeck coefficient S = -111 mu V/K at 600 K. Its power factor (S-2 center dot sigma) is 1.2 x 10(-3)Wm(-1)K(-2), twofold better than films deposited on crystalline SrTiO3 under the same experimental conditions. Using our measured thermal conductivity (kappa) at 300K (4.89Wm(-1)K(-1)), the figure of merit, ZT = (S-2 center dot sigma center dot T/kappa), is calculated as 0.045 at 600 K, 5 times larger than ZT of our previously reported bulk ZnO. (C) 2014 The Japan Society of Applied Physics. |
| 61. |
Kunihisa Kato, Yoshika Hatasako, Makoto Kashiwagi, Harutoshi Hagino, Chihaya Adachi, Koji Miyazaki, Fabrication of a Flexible Bismuth Telluride Power Generation Module Using Microporous Polyimide Films as Substrates, JOURNAL OF ELECTRONIC MATERIALS, 10.1007/s11664-013-2852-0, 43, 6, 1733-1739, 2014.06, In this study, we investigated the effect of the structure of microporous p-type (Bi0.4Te3Sb1.6) and n-type (Bi2.0Te2.7Se0.3) BiTe-based thin films on their thermoelectric performance. High-aspect-ratio porous thin films with pore depth greater than 1 mu m and pore diameter ranging from 300 nm to 500 nm were prepared by oxygen plasma etching of polyimide (PI) layers capped with a heat-resistant block copolymer, which acted as the template. The cross-plane thermal conductivities of the porous p- and n-type thin films were 0.4 W m(-1) K-1 and 0.42 W m(-1) K-1, respectively, and the dimensionless figures of merit, ZT, of the p- and n-type BiTe films were estimated as 1.0 and 1.0, respectively, at room temperature. A prototype thermoelectric module consisting of 20 pairs of p- and n-type strips over an area of 3 cm x 5 cm was fabricated on the porous PI substrate. This module produced an output power of 0.1 mW and an output voltage of 0.6 V for a temperature difference of 130A degrees C. The output power of the submicrostructured module was 1.5 times greater than that of a module based on smooth BiTe-based thin films. Thus, the thermoelectric performance of the thin films was improved owing to their submicroscale structure.. |
| 62. |
Makoto Kashiwagi, Zhouya Zheng, Kimito Ishihara, Makoto Egami, Koji Miyazaki, Spectral Absorptance Enhancement of a Gold Coated Micro-particle Array, Proceedings of NanoRad 2014, 2014.06. |
| 63. |
S. L Saini, P. Mele, H. Honda, K. Matsumoto, K. Miyazaki, A. Ichinose, Thermoelectric Properties of Al-Doped ZnO Thin Films, JOURNAL OF ELECTRONIC MATERIALS, 10.1007/s11664-014-2992-x, 43, 6, 2145-2150, 2014.06, We have prepared 2 % Al-doped ZnO (AZO) thin films on SrTiO3 substrates by a pulsed laser deposition technique at various deposition temperatures (T (dep) = 300-600 A degrees C). The thermoelectric properties of AZO thin films were studied in a low temperature range (300-600 K). Thin film deposited at 300 A degrees C is fully c-axis-oriented and presents electrical conductivity 310 S/cm with Seebeck coefficient -65 mu V/K and power factor 0.13 x 10(-3) Wm(-1) K-2 at 300 K. The performance of thin films increases with temperature. For instance, the power factor is enhanced up to 0.55 x 10(-3) Wm(-1) K-2 at 600 K, surpassing the best AZO film previously reported in the literature.. |
| 64. |
Kunihisa Kato, Yoshika Hatasako, Michitaka Uchino, Yasukazu Nakata, Yoshinori Suzuki, Teruaki Hayakawa, Chihaya Adachi, Koji Miyazaki, Flexible Porous Bismuth Telluride Thin Films with Enhanced Figure of Merit using Micro-Phase Separation of Block Copolymer, ADVANCED MATERIALS INTERFACES, 10.1002/admi.201300015, 1, 2, 2014.04. |
| 65. |
Paolo Mele, Hiroyuki Kamei, Hiroyuki Yasumune, Kaname Matsumoto, Koji Miyazaki, Development of thermoelectric module based on dense Ca3Co4O9 and Zn0.98Al0.02O legs, METALS AND MATERIALS INTERNATIONAL, 10.1007/s12540-014-2024-7, 20, 2, 389-397, 2014.03, Ca3Co4O9 (p-type) and Zn0.98Al0.02O (n-type) pellets were prepared by conventional sintering (CS) and Spark Plasma sintering (SPS) starting from the oxides. The best p-type sample was SPS Ca3Co4O9 obtained from pre-sintered pellets, with electrical conductivity sigma = 144 S/cm and Seebeck coefficient S = 172 mu V/K at 800 A degrees C, while thermal conductivity kappa = 2.00 W/mxK and figure of merit ZT = 0.23. The best n-type sample was CS Zn0.98Al0.02O showing sigma = 83 S/cm and S = -268 mu V/K at 800 A degrees C, while = 5.03 W/mxK and ZT = 0.127. The output power of a module based on SPS Ca3Co4O9 and CS Zn0.98Al0.02O legs was 2.26 mW (with T = 500 A degrees C, Delta T = 248 A degrees C).. |
| 66. |
Harutoshi Hagino, Masahiro Hokazono, Koji Miyazaki, Hiroaki Anno, Naoki Toshima, In-plane thermal conductivity of PEDOT-PSS thin films, (ISTP-24）, 2013.11. |
| 67. |
Kunihisa Kato, Hisashi Iwata, Koji Miyazaki, Thermoelectric Properties of Printed Bismuth Telluride Films, (第25回相変化研究会シンポジウム), 2013.11. |
| 68. |
Kunihisa Kato, Hisashi Iwata, Tsuyoshi Muto, Takeshi Kondo, Koji Miyazaki, High Performance Printable Thermoelectric Compound Using Heat Resistant Resin and Conductive Additive, Proceedings of ISMNT-4, 2013.10. |
| 69. |
Koji Miyazaki, Nano-porous thermoelectric thin films, （International Symposium on Applied Engineering & Sciences）, 2013.09. |
| 70. |
Harutoshi Hagino, Saburo Tanaka, Koji Miyazaki, Thermal and Electrical Conductivities of Porous Si Thin Films, (The 10th Asian Thermophysical Properties Confernce), 2013.09. |
| 71. |
M. Uchino, K. Kato, H. Hagino, K. Miyazaki, Fabrication by Coaxial-Type Vacuum Arc Evaporation Method and Characterization of Bismuth Telluride Thin Films, JOURNAL OF ELECTRONIC MATERIALS, 10.1007/s11664-012-2438-2, 42, 7, 1814-1819, 2013.07, We prepared both n- and p-type bismuth telluride thin films by using a coaxial-type vacuum arc evaporation method. The atomic compositions of the as-grown thin films and several annealed thin films were comparable to that of bulk bismuth telluride. Their thermoelectric properties were measured and found to be comparable to those of bulk materials. The Seebeck coefficient and electrical conductivity of the as-grown thin films were improved by the annealing process. The measured figures of merit (ZT) of the films were 0.86 for the n-type and 0.41 for the p-type at 300 K for annealing temperatures of 573 K and 523 K, respectively.. |
| 72. |
Kunihisa Kato, Harutoshi Hagino, Koji Miyazaki, Fabrication of bismuth telluride thermoelectric films containing conductive polymers using a printing method, Journal of Electronic Materials, 10.1007/s11664-012-2420-z, 42, 7, 1313-1318, 2013.07, We prepared a mixture of thermoelectric bismuth telluride particles, a conductive polymer [poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)], poly(acrylic acid) (PAA) and several organic additives to fabricate thermoelectric films using printing or coating techniques. In the mixture, the organic components (PEDOT:PSS, PAA and an additive) act as a binder to connect bismuth telluride particles mechanically and electrically. Among the organic additives used, glycerol significantly enhanced the electrical conductivity and bismuth telluride particle dispersibility in the mixture. Bi0.4Te3.0Sb1.6 films fabricated by spin-coating the mixture showed a thermoelectric figure of merit (ZT) of 0.2 at 300 K when the Bi0.4Te3Sb1.6 particle diameter was 2.8 μm and its concentration in the elastic films was 95 wt.%. © 2013 TMS.. |
| 73. |
P. Mele, S. Saini, H. Honda, K. Matsumoto, K. Miyazaki, H. Hagino, A. Ichinose, Effect of substrate on thermoelectric properties of Al-doped ZnO thin films, Applied Physics Letters, 10.1063/1.4812401, 102, 25, 2013.06, We have prepared 2% Al doped ZnO (AZO) thin films on SrTiO3 (STO) and Al2O3 substrates by Pulsed Laser Deposition technique at various deposition temperatures (Tdep = 300°C-600°C). Transport and thermoelectric properties of AZO thin films were studied in low temperature range (300 K-600 K). AZO/STO films present superior performance respect to AZO/Al2O3 films deposited at the same temperature, except for films deposited at 400°C. Best film is the fully c-axis oriented AZO/STO deposited at 300°C, which epitaxial strain and dislocation density are the lowest: electrical conductivity 310 S/cm, Seebeck coefficient -65 μV/K, and power factor 0.13 × 10-3 W m-1 K-2 at 300 K. Its performance increases with temperature. For instance, power factor is enhanced up to 0.55 × 10 -3 W m-1 K-2 at 600 K, surpassing the best AZO film previously reported in literature. © 2013 AIP Publishing LLC.. |
| 74. |
Masayuki Takashiri, Saburo Tanaka, Koji Miyazaki, Growth of single-crystalline bismuth antimony telluride nanoplates on the surface of nanoparticle thin films, JOURNAL OF CRYSTAL GROWTH, 10.1016/j.jcrysgro.2013.03.028, 372, 199-204, 2013.06, We have reported the growth of single-crystalline bismuth antimony telluride nanoplates on the surface of nanoparticle thin films using a simple sintering process. We prepared two types of bismuth antimony telluride thin films, one comprising nanoparticles and the other submicron particles. The nanoplates were found to grow only on thin films comprising nanoparticles. The structure, composition, and morphology of nanoplates were investigated by using X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray analysis. The obtained nanoplates were of length 0.5-1 mu m and thickness less than 100 nm. The atomic composition of the nanoplates was almost the same as that of the nanoparticles in the thin films. The nanoplates were found to be single crystalline, while the nanoparticles in the thin films were polycrystalline in nature. The growth of nanoplates on the surface of the thin films was due to the partial melting and evaporation of nanoparticles during the sintering process. As a result, the evaporated materials formed nuclei on the surface of the films, which then crystallized to form nanoplates. (C) 2013 Elsevier B.V. All rights reserved.. |
| 75. |
Michitaka Uchino, Akihiro Yamamoto, Kunihisa Kato, Koji Miyazaki, Bismuth-telluride thermoelectric thin films prepared by coaxial type vacuum arc evaporation method, (IFHT2012), 2012.11. |
| 76. |
Kunihisa Kato, Yoshika Hatasako, Michitaka Uchino, Yasukazu Nakata, Yoshinori Suzuki, Teruaki Hayakawa, Chihaya Adachi, Koji Miyazaki, Fabrication of porous bismuth telluride thin films using micro-phase separation of block copolymer, (IFHT2012), 2012.11. |
| 77. |
Yosuke Kawahara, Harutoshi Hagino, Hisashi Iwata, Koji Miyazaki, In-plane Thermal and Electrical Conductivity of Si Thin Film with Periodic Microporous, (IFHT2012), 2012.11. |
| 78. |
Masayuki Takashiri, Saburo Tanaka, Harutoshi Hagino, Koji Miyazaki, Combined effect of nanoscale grain size and porosity on lattice thermal conductivity of bismuth-telluride-based bulk alloys, JOURNAL OF APPLIED PHYSICS, 10.1063/1.4759326, 112, 8, 084315, 2012.10, Here, we investigate the combined effect of the nanoscale crystal grains and porosity on the lattice thermal conductivity of bismuth-telluride-based bulk alloys using both experimental studies and modeling. The fabricated bulk alloys exhibit average grain sizes of 30 |
| 79. |
Harutoshi Hagino, Yousuke Kawahara, Hisashi Iwata, Koji Miyazaki, Effects of Micro-Structures on In-plane Thermal Conductivity and Electrical Conductivity of Silicon Thin Film, (EIGHTEENTH SYMPOSIUM ON THERMOPHYSICAL PROPERTIES), 2012.06. |
| 80. |
Akihiro Yamamoto, Harutoshi Hagino, Yoshihiro Hashimoto, Koji Miyazaki, The Effects of Thermoelectric Film Thickness on Performance of In-Plane Thermoelectric Modules, JOURNAL OF ELECTRONIC MATERIALS, 10.1007/s11664-012-2067-9, 41, 6, 1799-1804, 2012.06, We fabricated in-plane thermoelectric modules (4 mm x 4 mm) on a 4-m-thick substrate using a vacuum deposition process through a shadow mask. In this study, a thermoelectric - pair was established using multilayered films of and thermoelectric thin films and an insulator film with a hole at the center. The output power was 58 nW at 443 K using the multilayered microgenerator. We discuss the effects of device thickness on the efficiency of the microgenerator to increase the output electric power. We evaluated the output power of the in-plane thermoelectric generator with a substrate using a one-dimensional heat conduction model, and it was found to depend on the thickness of the thermoelectric film. If the thermoelectric film is very thin, the power factor is more important than the nondimensional figure of merit, . Metal thin films with high power factor are more efficient than semiconductors with low power factors even though their thermal conductivities are high. When the thermoelectric thin film is thick, should be higher for larger output power of the device.. |
| 81. |
Koji Miyazaki, Saburo Tanaka, Daisuke Nagai, Heat Conduction of a Porous Material, JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME, 10.1115/1.4005709, 134, 5, 051018-1-051018-7, 2012.05, In this study, we introduce our numerical and experimental works for the thermal conductivity reduction by using a porous material. Recently thermal conductivity reduction has been one of the key technologies to enhance the figure of merit (ZT) of a thermoelectric material. We carry out numerical calculations of heat conduction in porous materials, such as phonon Boltzmann transport (BTE) and molecular dynamics (MD) simulations, in order to investigate the mechanism of the thermal conductivity reduction of a porous material. In the BTE, we applied the periodic boundary conditions with constant heat flux to calculate the effective thermal conductivity of porous materials.In the MD simulation, we calculated the phonon properties of Si by using the Stillinger-Weber potential at constant temperature with periodic boundary conditions in the x, y, and z directions. Phonon dispersion curves of single crystal of Si calculated from MD results by time-space 2D FFT are agreed well with reference data. Moreover, the effects of nanoporous structures on both the phonon group velocity and the phonon density of states (DOS) are discussed. At last, we made a porous p-type Bi2Te3 by nanoparticles prepared by a beads milling method. The thermal conductivity is one-fifth of that of a bulk material as well as keeping the same Seebeck coefficient as the bulk value. However, electrical conductivity was much reduced, and the ZT was only 0.048. [DOI: 10.1115/1.4005709]. |
| 82. |
Koji Miyazaki, Hiroki Osawa, Reflectance of Photonic Crystals of Self-assembled Silica Particles, Proceedings of International Workshop on Nano-Micro Thermal Radiation, 44-45, 2012.05. |
| 83. |
Hiroki Osawa, Ryota Nakano, Kazune Takubo, Koji Miyazaki, Spectral Absorptance of Micro-structures of Self-assembled Silica Particles, Proceedings of International Workshop on Nano-Micro Thermal Radiation, 120-121, 2012.05. |
| 84. |
Harutoshi Hagino, Yousuke Kawahara, Aimi Goto, Toru Hiwada, Koji Miyazaki, In-Plane Thermal Conductivity and Electrical Conductivity Measurements of Silicon Thin Film, Proceedings of The Eighth KSME-JSME Thermal and Fluids Engineering Conference, 2012.03. |
| 85. |
Kunihisa Kato, Yoshika Hatasako, Yasukazu Nakata, Yoshinori Suzuki, Teruaki Hayakawa, Chihaya Adachi, Koji Miyazaki, Thermal Conductivity of Bismuth Antimony Telluride Thin Films formed on Porous Films Prepared from Block Copolymer, Proceedings of The Eighth KSME-JSME Thermal and Fluids Engineering Conference, 2012.03. |
| 86. |
Harutoshi Hagino, Yosuke Kawahara, Aimi Goto, Koji Miyazaki, Effects of Micro-Structures on Thermal Conductivity and Electrical Conductivity, (6th EEIGM International Confernce Advanced Materials Research), 2011.11. |
| 87. |
Mao Sumino, Kentaro Harada, Masaaki Ikeda, Saburo Tanaka, Koji Miyazaki, Chihaya Adachi, Thermoelectric Properties of n-type C60 Thin Films and Their Application in Organic Thermovoltaic Devices (共著）, Applied Physics Letters, 10.1063/1.3631633, 99, 9, 093308, 2011.08. |
| 88. |
Koji Miyazaki, Enhanced Figure of Merit of a Porous Thin Film of Bismuth Antimony Telluride, The 5th KOREA-JAPAN Joint Seminar on Heat Transfer, 127-141, 2011.05. |
| 89. |
Makoto Kashiwagi, Shuzo Hirata, Kentaro Harada, Yanqiong Zheng, Koji Miyazaki, Masayuki Yahiro, Chihaya Adachi, Enhanced Figure of Merit of a Porous Thin Film of Bismuth Antimony Telluride （共著）, Applied Physics Letters, 10.1063/1.3543852, 98, 2, 023114, 2011.01. |
| 90. |
Yanqiong Zheng, Yuki Kubowaki, Makoto Kashiwagi, Koji Miyazaki, Process Optimization of Preparing Honeycomb-patterned Polystyrene Films by Breath Figure Method （共著）, Journal of Mechanical Science and Technology, 10.1007/s12206-010-1010-3, 25, 1, 33-36, 2011.01. |
| 91. |
Masayuki Takashiri, Saburo Tanaka, Koji Miyazaki, Improved Thermoelectric Performance of Highly-oriented Nanocrystalline Bismuth Antimony Telluride Thin Films （共著）, Thin Solid Films, 10.1016/j.tsf.2010.08.013, 519, 2, 619-624, 2010.11. |
| 92. |
Kentaro Harada, Mao Sumino, Chihaya Adachi, Saburo Tanaka, Koji Miyazaki, Improved Thermoelectric Performance of Organic Thin-film Elements Utilizing a Bilayer Structure of Pentacene and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimetane(F4-TCNQ) （共著）, Applied Physics Letters, 10.1063/1.3456394, 96, 25, 253304, 2010.06. |
| 93. |
Masayuki Takashiri, Saburo Tanaka, Koji Miyazaki, Hiroshi Tsukamoto, Cross-plane thermal conductivity of highly oriented nanocrystalline bismuth antimony telluride thin films, JOURNAL OF ALLOYS AND COMPOUNDS, 10.1016/j.jallcom.2009.10.117, 490, 1-2, L44-L47, 2010.02, The cross-plane thermal conductivity of highly oriented nanocrystalline bismuth antimony telluride thin films is investigated. The thin film was deposited by a flash evaporation method. The resulting film was oriented with the c-axis to the substrate, and was composed of fine grains with an average grain size of 150 nm. The cross-plane thermal conductivity of the film was measured by a 3 omega method at room temperature, and was determined to be 0.6 W m(-1) K(-1). Compared to the single crystal bulk alloy of nearly the same composition and carrier concentration, the thin film exhibited a 20% reduction in the thermal conductivity. (c) 2009 Elsevier B.V. All rights reserved.. |
| 94. |
Takatoshi Nishio, Makoto Kashiwagi, Koji Miyazaki, Masayuki Yahiro, Chihaya Adachi, Preparation of Nano-Porous Polymer Films having the Smallest Size of 80nm under High Humidity Conditions, 2009 MRS Fall meeting, 2009.12. |
| 95. |
Yuki Kubowaki, Koji Miyazaki, Numerical Calculation of A Nano-Porous Polymer Film Processing, 5th Taiwan-Japan Workshop on Mechanical and Aerospace Engineering, 111-115, 2009.10. |
| 96. |
Yuki Kubowaki, Koji Miyazaki, Numerical Calculation for Fabrication of a Nano-Porous Polymer Film, Proceedings of 1st Asian Conference on Organic Electronics(A-COE), 128-129, 2009.09. |
| 97. |
Satoaki Ikeuchi, Saburo Tanaka, Koji Miyazaki, Evaluation of Thermal Conductivity in BiTe Thin Film, Proceedings of International Conference on Thermoelectrics, 2009.07. |
| 98. |
J. Kurosaki, A. Yamamoto, S. Tanaka, J. Cannon, K. Miyazaki, H. Tsukamoto, Fabrication and Evaluation of a Thermoelectric Microdevice on a Free-Standing Substrate, JOURNAL OF ELECTRONIC MATERIALS, 10.1007/s11664-009-0819-y, 38, 7, 1326-1330, 2009.07, Using shadow masks prepared by standard microfabrication processes, we fabricated in-plane thermoelectric microdevices (4 mm x 4 mm) made of bismuth telluride thin films, and evaluated their performance. We used Bi0.4Te3.0Sb1.6 as the p-type semiconductor and Bi2.0Te2.7Se0.3 as the n-type semiconductor. We deposited p- and n-type thermoelectric thin films on a free-standing thin film of Si3N4 (4 mm x 4 mm x 4 mu m) on a Si wafer, and measured the output voltages of the microdevices while heating at the bottom of the Si substrate. The maximum output voltage of the thermoelectric device was 48 mV at 373 K.. |
| 99. |
Saburo Tanaka, Koji Miyazaki, Hiroshi Tsukamoto, Thermal Conductivity of Nano-porous Bismuth Telluride Thin Films, 17th Symposium on Thermophysical Properties, 398-398, 2009.06. |
| 100. |
Kei Ishikawa, Saburo Tanaka, Koji Miyazaki, Jun-ichiro Shiomi, Shigeo Maruyama, Thermal conductivity of vertically-aligned single-walled carbon nanotube film measured by 3 omega method, 2009 Material Research Society Spring Meeting, 4-4, 2009.04. |
| 101. |
Masahiro Kihara, Koji Miyazaki, Hiroshi Tsukamoto, Spectral Reflectance of the Close-Packed Structure of Silica Microspheres, INTERNATIONAL JOURNAL OF THERMOPHYSICS, 10.1007/s10765-008-0483-0, 29, 6, 2136-2148, 2008.12, The spectral reflectance of microperiodic structures of silica microspheres was investigated. The electromagnetic dispersion relation in a close-packed structure of silica spheres is computed. The three-dimensional close-packed structures, self-assembled with silica microspheres (2 mu m and 3 mu m), were rapidly fabricated over a large area. Specular reflectance was measured by using Fourier transform-infrared spectroscopy (FT-IR). The experimental results were evaluated by a modification of Bragg's law, taking into account Snell's law of refraction, and calculations of multiple reflections and the scalar wave approximation method. In addition, to expand the reflection wavelength range, a double-layered sample was fabricated, and its spectral reflectance was determined.. |
| 102. |
Visualization and Numerical Analysis of Unsteady Flow in Pump Sump
Numerical and experimental studies were done on unsteady flow in a pump sump to study the generation of air core vortex and submerged vortex, which cause vibration and acoustic noise. The geometry of the free surface in the test pump sump was visualized by Moire method, and velocities near pump suction were measured by PIV. Unsteady flow in the pump sump was calculated using VOF method in a commercial CFD software, and calculated velocities as well as free surface geometry were compared with measured ones. The present study showed that CFD can capture unsteady flow in a pump sump with a reasonable accuracy, and that the air core vortex as well as submerged vortex can be predicted by CFD.. |
| 103. |
M. Takashiri, K. Miyazaki, S. Tanaka, J. Kurosaki, D. Nagai, H. Tsukamoto, Effect of grain size on thermoelectric properties of n-type nanocrystalline bismuth-telluride based thin films, JOURNAL OF APPLIED PHYSICS, 10.1063/1.2990774, 104, 8, 084302-1 - 084302, 2008.10, The effect of grain size on the thermoelectric properties of n-type nanocrystalline bismuth-telluride based thin films is investigated. We prepare the nanocrystalline thin films with average grain sizes of 10, 27, and 60 nm by a flash-evaporation method followed by a hydrogen annealing process. The thermoelectric properties, in terms of the thermal conductivity by a differential 3 omega method, the electrical conductivity, and the Seebeck coefficient are measured at room temperature and used to evaluate the figure of merit. The minimum thermal conductivity is 0.61 W m(-1) K(-1) at the average grain size of 10 nm. We also estimate the lattice thermal conductivity of the nanocrystalline thin films and compare it with a simplified theory of phonon scattering on grain boundaries. For nanosized grains, the lattice thermal conductivity of nanocrystalline thin films decreases rapidly for smaller grains, corresponding to the theoretical calculation. The figure of merit is also decreased as the grain size decreases, which is attributed to the increased number of defects at the grain boundaries. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.2990774]. |
| 104. |
Seiichi Tanaka, Shun Moriyama, Hiroshi Tsukamoto, Koji Miyazaki, Effects of Channel Geometry for a Diffuser/Nozzle Valveless Micropump, The Seventh JSME-KSME Thermal and Fluids EngineeringConfernce, 158-158, 2008.10. |
| 105. |
Young-Joon Kim, Koji Miyazaki, Hiroshi Tsukamoto, Leak detection in pipe using transient flow and genetic algorithm, JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY, 10.1007/s12206-008-0735-8, 22, 10, 1930-1936, 2008.10, An inverse transient method with genetic algorithm (GA) was applied to leak detection in pipeline. Transient flow caused by valve operation was calculated using the characteristics method. The location and discharge of leak were determined so that the difference of the calculated pressure may be minimized from the reference pressure calculated under a given leak condition. Calculations were done for the leak at one and two locations in pipeline. Furthermore, the effect of noise in pressure data was discussed, and the leak locations and leak discharges can he predicted precisely even in the case of noisy data.. |
| 106. |
Saburo Tanaka, Yousuke Shimizu, Koji Miyazaki, Hiroshi Tsukamoto, Thermal Conductivity of Nano-Structured Bismuth Telluride Thin Films, The Seventh JSME-KSME Thermal and Fluids EngineeringConfernce, 19-19, 2008.10. |
| 107. |
Daisuke Nagai, Naohiro Otani, Koji Miyazaki, Hiroshi Tsukamoto, Zone folding effects of heat conduction in nano-porous silicon, The Seventh JSME-KSME Thermal and Fluids EngineeringConfernce, 6-6, 2008.10. |
| 108. |
黒崎潤一郎, 山本明宏, 田中三郎, 宮崎康次, 塚本寛, In-Plane Termoelectric Micro-Generator on a Free StandingG Si_3N_4 Thin Film, Proceedings of the 2nd International Forum on Heat Transfer, 5-5, 2008.09. |
| 109. |
田中誠一, 森山瞬, 塚本寛, 宮崎康次, Scale effect for diffuser/nozzle valveless micropump, Proceedings of the 2nd International Forum on Heat Transfer, 7-7, 2008.09. |
| 110. |
永井大資, 城戸陽平, 宮崎康次, 塚本寛, Thermal Conduction of Si Nano-porous Structure, Proceedings of the 2nd International Forum on Heat Transfer, 23-23, 2008.09. |
| 111. |
石川桂, 田中三郎, 宮崎康次, 塩見淳一郎, 丸山茂夫, Thermal conductivity characterization of vertically-aligned single-walled carbon nanotube films, Proceedings of the 2nd International Forum on Heat Transfer, 2008.09. |
| 112. |
田中三郎, 高尻雅之, 宮崎康次, 塚本寛, Thermoelectric Properties of Nano-Structured Bismuth TellurideThin Films, Proceedings of the 2nd International Forum on Heat Transfer, 114-114, 2008.09. |
| 113. |
M. Takashiri, S. Tanaka, M. Takiishi, M. Kihara, K. Miyazaki, H. Tsukamoto, Preparation and characterization of Bi0.4Te3.0Sb1.6 nanoparticles and their thin films, JOURNAL OF ALLOYS AND COMPOUNDS, 10.1016/j.jallcom.2007.08.054, 462, 1-2, 351-355, 2008.08, In this article, we perform a preliminary study to assemble micro-size thermoelectric devices with low-cost fabrication by a preparation of nanoparticles and their thin films. Bi0.4TC3.0Sb1.6 nanoparticles with an average size of approximately 50nm are fabricated by a beads-milling method. The nanoparticle solution is prepared by mixing with toluene and a surfactant, and thin films with 1 mu m thick are deposited on Al2O3 substrates by a printing method. The thin films are sintered at temperatures ranging from 300 to 500 degrees C for 60 min in hydrogen ambient. We investigate the thin film structures and the thermoelectric properties at room temperature. As the sintering temperature increases, hexagonal-shaped crystals are grown on the film surface while the atomic composition is almost constant throughout all the sintering temperatures. The XRD patterns indicate that all the nanoparticle thin films are found to mostly exhibit the same XRD intensities and have multiple peaks correspond to each other. The in-plane electrical conductivity of the thin films increases but. the Seebeck coefficient decreases as the sintering temperature increases. As a result, the best performance of the thermoelectric power factor of 1.3 mu W/(cm K-2) is achieved at a sintering temperature of 350 degrees C. (C) 2007 Elsevier B.V. All rights reserved.. |
| 114. |
Jun-ichiro Kurosaki, Akihiro Yamamoto, Saburo Tanaka, Koji Miyazaki, Hiroshi Tsukamoto, The fabrication and evaluation of the thermoelectric micro-generator on a free-standing substrate, 27th International conference on thermoelectrics, 6 pages, 2008.08, 主要論文集（会議）. |
| 115. |
M. Takashiri, K. Miyazaki, H. Tsukamoto, Structural and thermoelectric properties of fine-grained Bi(0.4)Te(3.0)Sb(1.6) thin films with preferred orientation deposited by flash evaporation method, THIN SOLID FILMS, 10.1016/j.tsf.2007.12.130, 516, 18, 6336-6343, 2008.07, Structural and thermoelectric properties of p-type fine-grained Bi(0.4)Te(3.0)Sb(1.6) thin films are investigated. The films are deposited by a flash evaporation method and exhibit a preferred orientation in the c-axis direction. By optimizing deposition conditions, we achieve thin films with clean surfaces. Then in order to enhance the crystallinity with preferred orientation, as well as the thermoelectric properties of the thin films, they are annealed in hydrogen ambient at atmospheric pressure and at temperatures ranging from 200 to 350 'C. The cross-section microstructure and crystallinity of the thin films are investigated by scanning electron microscopy and X-ray diffraction, respectively. The electrical conductivity, Seebeck coefficient, and thermoelectric power factor are measured at room temperature. We confirm that the grain growth and the crystallization along the c-axis are enhanced as the annealing temperature increases. The highest performance of p-type Bi(0.4)Te(3.0)Sb(1.6) thin films observed in this study have an annealing temperature of 300 degrees C, resulting in a thennoelectric power factor of 34.9 mu W cm(-1) K(-2) at the average grain size of 88 nm. We consider that the synthesis conditions reduce the number of potential scattering sites at grain boundaries and defects, thus improving the thermoelectric power factor. (c) 2007 Elsevier B.V All rights reserved.. |
| 116. |
Leak Detection in Pipe Using Genetic Algorithm and Inverse Transient Method : (2nd Report, Leaks at Two Points)
Leak detection for leaks at two points was done using the inverse transient method and genetic algorithm. The locations and discharges of each leak were selected as GA parameters for leaks at two points in pipeline. The steady pressures and leak discharges at all nodes were calculated using Newton iteration method. Calculations under assumption of two leaks points were done for not only leaks at two points but also leak at one point in pipeline. Furthermore, the effect of noise in pressure data was discussed, and the leak locations and leak discharges can be predicted precisely even in the .... |
| 117. |
Kei Ishikawa, Saburo Tanaka, Koji Miyazaki, Jun-ichiro Shiomi, Shigeo Maruyama, Thermal conductivity of vertically-aligned single-walled carbon nanotube film measured by 3omega method, APS March Meeting, D24.00008-D24.00008, 2008.03. |
| 118. |
Leak Detection in Pipe Using Genetic Algorithm and Inverse Transient Method. |
| 119. |
非対称流路を利用したバルブレスマイクロポンプ. |
| 120. |
Saburo Tanaka, Koji Miyazaki, Hiroshi Tsukamoto, Masayuki Takashiri, Fabrication of Nanoparitcle P-type Bismuth Telluride Thin Films and Their Thermoelectric Properties, 7th Pacific RIM conference on ceramic and glass technology, 2007.11. |
| 121. |
Masahiro Kihara, Ryosuke Sameshima, Koji Miyazaki, Hiroshi Tsukamoto, Directional Spectral Emittance of Close-packed Silica Micro-Spheres, Proceedings of the Asian Thermophysical Properties Conference, 102-102, 2007.08. |
| 122. |
M. Takashiri, T. Shirakawa, K. Miyazaki, H. Tsukamoto, Fabrication and characterization of bismuth-telluride-based alloy thin film thermoelectric generators by flash evaporation method, SENSORS AND ACTUATORS A-PHYSICAL, 10.1016/j.sna.2007.05.030, 138, 2, 329-334, 2007.08, Bismuth-telluride-based alloy thin film thermoelectric generators are fabricated by a flash evaporation method. We prepare Bi0.4Te3.0Sb1.6 (P-type) and Bi2.0Te2.7Se0.3 (n-type) powders for the fabrication of the flash evaporated thin films. The overall size of the thin film thermoelectric generators, which consist of seven pairs of legs connected by aluminum electrodes, is 20 mm by 15 mm. Each leg is 15 turn long, 1 turn wide and 1 mu m thick. We measure the output voltage and estimate the maximum output power near room temperature as a function of the temperature difference between hot and cold junctions of the thin film thermoelectric generators. In order to improve the performance of the generators, a hydrogen annealing process is carried out at several temperatures from 25 degrees C to 250 degrees C. The highest output voltage of 83.3 mV and estimated Output power of 0.21 mu W are obtained from a hydrogen annealing temperature of T-a = 250 degrees C and a temperature difference of Delta T = 30 K. The hydrogen annealing temperature of T-a = 250 degrees C also results in the best electrical performance for both p-type thin film (Seebeck coefficient= 254.4 mu V/K, resistivity = 4.1 m Omega cm, power factor = 15.9 mu W/cm K-2) and n-type thin film (- 179.3 mu V/K, 1.5 m Omega cm, 21.5 mu W/cm K-2). (C) 2007 Elsevier B.V. All rights reserved.. |
| 123. |
M. Takashiri, T. Shirakawa, K. Miyazaki, H. Tsukamoto, Fabrication and characterization of Bi0.4Te3.0Sb1.6 thin films by flash evaporation method, JOURNAL OF ALLOYS AND COMPOUNDS, 10.1016/j.jallcom.2006.09.136, 441, 1-2, 246-250, 2007.08, Bi0.4Te3.0Sb1.6 thin films on glass substrates are fabricated by a flash evaporation method. In order to enhance the transport properties of the thin films, annealing in argon ambient at atmospheric pressure is carried out for 1 h in the temperature range from 200 to 400 degrees C. The structure of the thin films, in terms of homogeneous composition and crystallinity, is investigated by energy dispersive X-ray spectroscopy and X-ray diffraction, respectively. The microstructure of the thin films is examined using scanning electron microscopy. We confirm that as-deposited Bi0.4Te3.0Sb1.6 thin films have a mostly homogeneous structure except for a few extra stuck particles. At higher annealing temperatures, the crystallinity of the thin films is improved and the size of crystal grains increases to the same size as the film thickness. However, excessive high annealing temperatures cause porous thin films due to the evaporation of tellurium. The transport properties of the thin films, in terms of the electrical resistivity, the Seebeck coefficient and the thermoelectric power factor are determined at room temperature. By optimizing the annealing conditions, it is possible to obtain a high-performance thin film with a thermoelectric power factor of 12.2 mu W cm(-1) K-2. We consider that the performance of the thin films is enhanced for optimized annealing because of reductions in the importance of grain boundary scattering. (C) 2006 Elsevier B.V. All rights reserved.. |
| 124. |
Koji Miyazaki, Yoshizumi Iida, Daisuke Nagai, Hiroshi Tsukamoto, Numerical Analysis of Heat Conduction in Nanostructured Silicon, Proceedings of the Asian Thermophysical Properties Conference, 147-152, 2007.08. |
| 125. |
Atsushi Sakurai, Shigenao Maruyama, Koji Miyazaki, Atsuki Komiya, Phonon Transport Simulation for Nano/Microscale Heat Conduction, Proceedings of the Asian Thermophysical Properties Conference, 100-105, 2007.08. |
| 126. |
M. Takashiri, M. Takiishi, S. Tanaka, K. Miyazaki, H. Tsukamoto, Thermoelectric properties of n-type nanocrystalline bismuth-telluride-based thin films deposited by flash evaporation, JOURNAL OF APPLIED PHYSICS, 10.1063/1.2717867, 101, 7, 074301.1-074301.5, 2007.04, The thermal conductivity of n-type nanocrystalline bismuth-telluride-based thin films (Bi2.0Te2.7Se0.3) is investigated by a differential 3 omega method at room temperature. The nanocrystalline thin films are grown on a glass substrate by a flash evaporation method, followed by hydrogen annealing at 250 degrees C. The structure of the thin films is studied by means of atomic force microscopy, x-ray diffraction, and energy-dispersive x-ray spectroscopy. The thin films exhibit an average grain size of 60 nm and a cross-plane thermal conductivity of 0.8 W/m K. The in-plane electrical conductivity and in-plane Seebeck coefficient are also investigated. Assuming that the in-plane thermal conductivity of the thin films is identical to that of the cross-plane direction, the in-plane figure of merit of the thin films is estimated to be ZT=0.7. As compared with a sintered bulk sample with average grain size of 30 mu m and nearly the same composition as the thin films, the nanocrystalline thin films show approximately a 50% reduction in the thermal conductivity, but the electrical conductivity also falls 40%. The reduced thermal and electrical conductivities are attributed to increased carrier trapping and scattering in the nanocrystalline film. (c) 2007 American Institute of Physics.. |
| 127. |
Atsushi Sakurai, Shigenao Maruyama, Koji Miyazaki, Atsuki Komiya, Micro-Scale Heat Transport Modeling Using Equation of Phonon Radiative Transfer, Third International Conference on Flow Dynamics, 61-62, 2006.11. |
| 128. |
Masahiro Kihara, Koji Miyazaki, Hiroshi Tsukamoto, Reflectivity of Micro Periodic Structure with Silica Spheres, 17th International Symposium on Transport Phenomena, 2006.09. |
| 129. |
M. Takashiri, T. Borca-Tasciuc, A. Jacquot, K. Miyazaki, G. Chen, Structure and thermoelectric properties of boron doped nanocrystalline Si0.8Ge0.2 thin film, JOURNAL OF APPLIED PHYSICS, 10.1063/1.2337392, 100, 5, 054315-1, 2006.09, The structure and thermoelectric properties of boron doped nanocrystalline Si0.8Ge0.2 thin films are investigated for potential application in microthermoelectric devices. Nanocrystalline Si0.8Ge0.2 thin films are grown by low-pressure chemical vapor deposition on a sandwich of Si3N4/SiO2/Si3N4 films deposited on a Si (100) substrate. The Si0.8Ge0.2 film is doped with boron by ion implantation. The structure of the thin film is studied by means of atomic force microscopy, x-ray diffraction, and transmission electron microscopy. It is found that the film has column-shaped crystal grains similar to 100 nm in diameter oriented along the thickness of the film. The electrical conductivity and Seebeck coefficient are measured in the temperature range between 80-300 and 130-300 K, respectively. The thermal conductivity is measured at room temperature by a 3 omega method. As compared with bulk silicon-germanium and microcrystalline film alloys of nearly the same Si/Ge ratio and doping concentrations, the Si0.8Ge0.2 nanocrystalline film exhibits a twofold reduction in the thermal conductivitity, an enhancement in the Seebeck coefficient, and a reduction in the electrical conductivity. Enhanced heat carrier scattering due to the nanocrystalline structure of the films and a combined effect of boron segregation and carrier trapping at grain boundaries are believed to be responsible for the measured reductions in the thermal and electrical conductivities, respectively. (c) 2006 American Institute of Physics.. |
| 130. |
Kihara Masahiro, Koji Miyazaki, Hiroshi Tsukamoto, Reflectivity of Micro Periodic Structure Generated with Silica Microspheres, 16th Symposium on Thermophysical Properties, 2006.08. |
| 131. |
Koji Miyazaki, Toyotaka Arashi, Daisuke Makino, Hiroshi Tsukamoto, Heat conduction in microstructured materials, IEEE TRANSACTIONS ON COMPONENTS AND PACKAGING TECHNOLOGIES, 10.1109/TCAPT.2006.875905, 29, 2, 247-253, 2006.06, The phonon Boltzmann equation is solved numerically in order to study the phonon thermal conductivity of micro/nanostructured thin films with open holes in a host material. We focused on the size effect of embedded pores and film thickness on the decrease in thermal conductivity of the film. Simulations have revealed that the temperature profiles in the micro/nanostructured materials are very different from those in their bulk counterparts, due to the ballistic nature of the microscale phonon transport. These simulations clearly demonstrate that the conventional Fourier beat conduction equation cannot be applied to study heat conduction in solids at microscale. The effective thermal conductivity of thin films with micro/nanoholes is calculated from the applied temperature difference and the heat flux. In the present paper, the effective thermal conductivity is shown as a function of the size of the micro/nanoholes and the film thickness. For example, when the size of the hole becomes. approximately 1/20th the phonon mean free path in a film, the thickness is 1/10th the mean free path of phonons and the effective thermal conductivity decreases to as low as 6% of the bulk value. The distribution of holes also affects the reduction in the effective thermal conductivity. Thin films embedded with staggered-hole arrays have slightly lower effective thermal conductivities than films with aligned-hole arrays. The cross-sectional area in the thermal transport direction is a significant parameter with respect to the reduction of thermal conductivity. The results of the present study may prove useful in the development of artificial micro/nanostructured materials, including thermoelectrics and low-k dielectrics.. |
| 132. |
Masahiro Kihara, Koji Miyazaki, Hiroshi Tsukamoto, Reflectivity of Silica Micro Periodic Structures, Proceedings of ISMNT-2, 349-352, 2006.03. |
| 133. |
Hiroshi Tsukamoto, Koji Miyazaki, Development of an active controlled airfoil preventing flow separation, Proceedings of the 7th International Symposium on experimental and computational aerothermodynamics of internal flows, 259-264, 2005.09. |
| 134. |
Koji Miyazaki, Hiroshi Tsukamoto, Ronguii Yang, Gang Chen, Thermal conductivity of a nano-structured material, Proceedings of the fifth international conference on enhanced, compact and ultra-compact heat exchangers: Science, engineering and technology, 6-6, 2005.09. |
| 135. |
Koji Miyazaki, Alexandre Jaquot, Toshiteru Shirakawa, Masayuki Kozasa, Hiroshi Tsukamoto, n-type Bi2Te3 Thin Film Fabrication by Using a Flash Vapor Deposition Method, Proceedings of the 3rd Europeen Conference on Thermoelectrics, 116-118, 2005.09. |
| 136. |
Koji Miyazaki, Masahiro Kihara, Hiroshi Tsukamoto, Thermal Radiative Properties of Photonic Cryatals, 2005 ASME/Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems(InterPACK2005), 4-4, 2005.07. |
| 137. |
Masahiro Kihara, Koji Miyazaki, Hiroshi Tsukamoto, Measurement of the spectral directional reflectivity of silica photonic crystals, Proceedings of the Sixth World Conference on Experimental Heat Transfer, 144-145, 2005.04. |
| 138. |
Masahiro Kihara, Koji Miyazaki, Hiroshi Tsukamoto, Measurement of the spectral directional reflectivity of silica photonic crystals, Proceedings of the 6th KSME-JSME Thermal & Fluids Engineering Conference, 2005.03. |
| 139. |
Koji Miyazaki, Daisuke Makino, Hiroshi Tsukamoto, Gang Chen, Numerical simulations of Heat transfer in Nanoscopic area, Proceedings of the 6th KSME-JSME Thermal & Fluids Engineering Conference, 2005.03. |
| 140. |
Makoto Kidera, Kenta Toh, Hiroshi Tsukamoto, Koji Miyazaki, Numerical study on Y-shaped Valve-less Micro-pump, Proceedings of the 6th KSME-JSME Thermal & Fluids Engineering Conference, 2005.03. |
| 141. |
Koji Miyazaki, Hiroshi Tsukamoto, Gang Chen, Thermal conductivities of nano-structured materials, Proceedings of the 1st International Forum on Heat Transfer, 215-216, 2004.11. |
| 142. |
Hiroshi TSUKAMOTO, Koji MIYAZAKI, Tsutomu IWAKO, Hiroshi FUNAKOSHI, Hong WANG, Study on Diffuser Pump Instability at Off-Desing Conditions, 22nd IAHR Symposium on Hydraulic Machinery and Systems June 29-July 2,2004 Stockholm-Sweden, B, B10-1.doc-1-B10-1.doc-10, 2004.07. |
| 143. |
Toyotaka Arashi, Koji Miyazaki, Hiroshi Tsukamoto, Numerical Simulations of Boltzmann Equations for Heat transfer at Microscopic Area, Thermal Science & Engineering, 12, 4, 71-72, 2004.04. |
| 144. |
Koji Miyazaki, Gang Chen, Hiroshi Tsukamoto, Fabrication of Photonic Crystals for the Control of the Radiative Properties, Proceedings of The first International Symposium on Micro & Nano Technology, 2004.03. |
| 145. |
Soichi Niino, Hiroshi Tsukamoto, Koji Miyazaki, Numerical Simulation of Centrifugal Blood Pumps for the Improvement of Antithrombogenecity, Proceedings of International Symposium on Bio-inspired Systems 2004, 2, 101-105, 2004.01. |
| 146. |
Masahiro Kihara, Koji Miyazaki, Hiroshi Tsukamoto, Radiative Properties of Bio-mimetic Photonic Crystals, Proceedings of International Symposium on Bio-inspired Systems 2004, 2, 106-109, 2004.01. |
| 147. |
Koji Miyazaki, Hiroshi Tsukamoto, Shinichi Hirano, Motoki Ozaki, Molecular dynamics simulations on the thermal conductivity of Si-Ge superlattices, Proceedings of the International Symposium on Micro-Mechanical Engineering, 2003, 494-498, 2003.12, We conducted molecular dynamics (MD) simulations on heat transfer in Si-Ge superlattices to investigate the effects of nano-structures on thermal conductivities. Both the perpendicular thermal conductivity to the interfaces (cross-plane) and the parallel one to the interfaces (in-plane) were calculated. The layered system had a lower conductivity than the uniform system. When the number of layers was increased while keeping the total sample thickness constant, the cross-plane thermal conductivity decreased. We calculated the kinetic energy profile to investigate the mechanism of this decrease. The motions of atoms at the boundaries between Si and Ge were suppressed, and it became thermal resistance.. |
| 148. |
Koji MIYAZAKI, Hiroshi TSUKAMOTO, Toshiaki TAKAMIYA, Kazuya TAKAO, Temperature measurements with micro-TFTCs, The International Symposium on Micro-Mechanical Engineering, 2003, 461-466, 2003.12, We fabricate metal thin film thermocouples (TFTCs). Au-Pt, Cu-Ni, and W-Ni are deposited on a glass plate using standard thin film processes. The dimension of thermocouple junction is 30μm×300μm. The thermoelectric powers of TFTCs are different from those of bulk because diffusion of electrons is restricted by the very thin film. However TFTCs are still useful for temperature measurements because the thermoelectric voltage is proportional to measured temperature at thermocouple junction. The response time of Au-Pt TFTCs is about 30ns when the surface of the glass is heated by a YAG pulsed laser. The result compares favorably with measurements by a thermoreflectance method. We also describe W-Ni nano-TFTCs with micro-heater fabricated by Focused Ion Beam for the measurement of absolute temperature distribution in 10 micron area. In order to reduce the size of the TFTCs we employ a 3-dimensional structure.. |
| 149. |
Makoto KIDERA, Koji MIYAZAKI, Hiroshi TSUKAMOTO, Development of a Valve-less Micro-pump with an Asymmetric Micro-Channel, The 7th International Conference on Fluid Machinery, CDROM, 2003.10. |
| 150. |
Hiroshi Funakoshi, Hiroshi Tsukamoto, Koji Miyazaki, Kazuyoshi Miyagawa, Experimental study on unstable characteristics of mixed-flow pump at low flow-rates, ASME 2003 Fluids Engineering Division Summer Meeting, 10.1115/fedsm2003-45103, CDROM, 609-614, 2003.07. |
| 151. |
Ming ZHANG, Li-Jun LIU, Koji MIYAZAKI, Hiroshi TSUKAMOTO, Effect of Impeller Tip Leakage Flow on Hydrodynamic Forces, The Fifth JSME-KSME Fluids Engineering Conference, 1579-1584, 2002.11. |
| 152. |
Hong WANG, Makoto TAKAHASHI, Koji MIYAZAKI, Hiroshi TSUKAMOTO, Experimental Study of Unsteady Phenomena in a Diffuser Pump at Off-design Conditions, The Fifth JSME-KSME Fluids Engineering Conference, 1573-1578, 2002.11. |
| 153. |
K Miyazaki, T Inoue, Genetic algorithm simulation for deposited structure of atoms, SURFACE SCIENCE, 501, 1-2, 93-101, 2002.03, Molecular simulations using a genetic algorithm are conducted to investigate stable structures of clusters and deposited atoms on substrates. First, the stable structures of N-atom clusters are calculated. where an icosahedron is found to be the most stable form of a 13-atom cluster. Secondly, stable structures of deposited atoms on a solid surface are investigated. The simulation shows that deposited atoms have either an island or a layer structure, depending on the combination of intermolecular potentials between the deposited and substrate atoms. The present simulation is based on statics, which demands little computing power. (C) 2001 Elsevier Science B.V. All rights reserved.. |
| 154. |
Motoki Ozaki, Koji Miyazaki, Hiroshi Tsukamoto, Molecular dynamics simulation on the vibration of atoms in Si-Ge superlattices, Proceedings of ICEC 2001, CDROM, 2001.09. |
| 155. |
Koji MIYAZAKI, Kenji Seki, Akira Sugihara, Hiroshi Tsukamoto, Development of a bubble actuated micro pump, Proceedings of ASME Fluids Engineering Division Summer Meeting 2001, CDROM, 3, 176-181, 2001.06. |
| 156. |
Koji Miyazaki, Bao Yang, Arvind, Narayanaswamy, Gang Chen, Photonic and Radiative Properties of Bubble Arrays, Proceedings of 2001 ASME International Mechanical Engineering Congress, CDROM, 2001.04. |
| 157. |
Takayoshi Inoue, Yoshimasa Takahashi, Koji Miyazaki, Kunio Hijikata, Condensation Dynamic on a solid surface in Thin Film prcessing, Molecular and Micro-scale Heat transfer in Material Processing and other Applications, 119-128, 1997.04. |
| 158. |
Takao Nagasaki, Kunio Hijikata, Koji Miyazaki, Hirokazu Kaneko, Hiroki Itoh, Fundamental study on the Formation of Mctal Clusters, Molecular and Micro-scale Heat transfer in Material Processing and other Applications, 97-108, 1997.04. |
| 159. |
Koji Miyazaki, Kunio Hijikata, Takayoshi Inoue, Genetic Algorithm Simulation for Deposited Atoms, Proceedings of ASME IMECE, Micreelectro mechanical Systems (MEMS), PSC.62-HTP354, 199-204, 1997.04. |
| 160. |
Kunio Hijikata, Koji Miyazaki, Takayoshi Inoue, Osamu Nakabeppu, Nucleation in Thin Film Processing, Proceeding of ASME IMECE, Transport phenomena in Materials Processing and Manufacturing, HTP336-FEP240, 137-142, 1996.04. |
