| 1. |
Shinjiro Ono, Sung Hwa Hwang, Takamasa Okumura, Kunihiro Kamataki, Naoto Yamashita, Naho Itagaki, Kazunori Koga, Masaharu Shiratani, Jun-Seok Oh, Susumu Takabayashi, Tatsuyuki Nakatani, Raman spectral analysis of the as-deposited a-C:H films prepared by CH4+ Ar plasma CVD, MRS ADVANCES, 10.1557/s43580-022-00310-6, 7, 30, 718-722, 2022.11, Applicability of precise Raman spectral analysis of a-C:H films deposited using a plasma chemical vapor deposition (CVD) method has been discussed based on the sensitivity to initial conditions in peak separation. The spectral analysis offers to deconvolute the spectra into five peaks, while the as-deposited films prepared by plasma CVD is difficult to the five-peak separation. We found the peak position and the peak height ratio of the D-band to the G(+)-band can be employed to discuss the structure of the as-deposited films. We examined the structural difference between the films deposited at the powered electrode and that at grounded electrode. We found graphene nanoribbon-like structures may be formed in the films deposited on the grounded substrate. This result suggests that the substrate position is an important factor to form the graphene nanoribbon-like structure.. |
| 2. |
Susumu Toko, Masashi Ideguchi, Taiki Haseagawa, Takamasa Okumura, Kunihiro Kamataki, Kosuke Takenaka, Kazunori Koga, Masaharu Shiratani, Yuichi Setsuhara, Effect of gas flow rate and discharge volume on CO2 methanation with plasma catalysis, Japanese Journal of Applied Physics, 10.35848/1347-4065/ac4822, 2022.01. |
| 3. |
S. H. Hwang, R. Iwamoto, T. Okumura, K. Kamataki, N. Itagaki, K. Koga, T. Nakatani, M. Shiratani, Comparison between Ar+CH4 Cathode and Anode Coupled Capacitively Coupled Plasma Chemical Vapor Deposition of Hydrogenated Amorphous Carbon Films, Thin Solid Films, 10.1016/j.tsf.2021.138701, 729, 138701, 2021.07. |
| 4. |
S. H. Hwang, R. Iwamoto, T. Okumura, K. Kamataki, N. Itagaki, K. Koga, T. Nakatani, M. Shiratani, Comparison between Ar+CH4 Cathode and Anode Coupled Capacitively Coupled Plasma Chemical Vapor Deposition of Hydrogenated Amorphous Carbon Films, Thin Solid Films, 10.1016/j.tsf.2021.138701, 729, 2021.07. |
| 5. |
F. L. Chawarambwa, T. E. Putri, K. Kamataki, M. Shiratani, K. Koga, N. Itagaki, D. Nakamura, Synthesis of Yb3+/Ho3+ co-doped Y2O3 nanoparticles and its application to dye sensitized solar cells, J. Mol. Struct., 10.1016/j.molstruc.2020.129479, 1228, 129479, 2021.03. |
| 6. |
C. Suriyasak, K. Hatanaka, H. Tanaka, T. Okumura, D. Yamashita, P. Attri, K. Koga, M. Shiratani, N. Hamaoka, Y. Ishibashi, Alterations of DNA Methylation Caused by Cold Plasma Treatment Restore Delayed Germination of Heat-Stressed Rice (Oryza sativa L.) Seeds, ACS Agric. Sci. Technol., 10.1021/acsagscitech.0c00070, 1, 1, 5-10, 2021.02. |
| 7. |
P. Attri, K. Ishikawa, T. Okumura, K. Koga, M. Shiratani, V. Mildaziene, Impact of seed color and storage time on the radish seed germination and sprout growth in plasma agriculture, Sci. Rep., 10.1038/s41598-021-81175-x, 11, 1, 1-10, 2021.01. |
| 8. |
P. Attri, K. Koga, M. Shiratani, Possible impact of plasma oxidation on the structure of C-terminal domain of SARS-CoV-2 spike protein: a computational study, Jpn. J. Appl. Phys., 10.35848/1882-0786/abd717, 14, 2, 2021.01. |
| 9. |
T. E. Putri, Y. Hao, F. L. Chawarambwa, H. Seo, Min-Kyu Son, K. Kamataki, N. Itagaki, K. Koga, M. Shiratani, Effects of Activated Carbon Counter Electrode On Bifacial Dye Sensitized Solar Cells (DSSCs), Mater. Sci. Forum, 10.4028/www.scientific.net/MSF.1016.863, 1016, 863-868, 2021.01. |
| 10. |
V. Sirgedaitė‐Šėžienė , V. Mildažienė, P. Žemaitis , A. Ivankov , K. Koga, M. Shiratani, V. Baliuckas, Long-term response of Norway spruce to seed treatment with cold plasma: dependence of the effects on the genotype, Plasma Process Polym, 10.1002/ppap.202000159, 2020.12. |
| 11. |
T. Kawasaki, K. Koga, M. Shiratani, Experimental identification of the reactive oxygen species transported into a liquid by plasma irradiation, Jpn. J. Appl. Phys., 10.35848/1347-4065/abc3a1, 59, 11, 110502, 2020.11. |
| 12. |
F. L. Chawarambwa, T. E. Putri, M. K. Son, K. Kamataki, N. Itagaki, K. Koga, M. Shiratani, Graphene-Si3N4 nanocomposite blended polymer counter electrode for low-cost dye-sensitized solar cells, Chem. Phys. Lett., 10.1016/j.cplett.2020.137920, 758, 137920, 2020.11. |
| 13. |
S. H. Hwang, T. Okumura, K. Kamataki, N. Itagaki, K. Koga, M. Shiratani, Size and flux of carbon nanoparticles synthesized by Ar+CH4 multi-hollow plasma chemical vapor deposition, Diam Relat Mater, 10.1016/j.diamond.2020.108050, 109, 108050, 2020.11. |
| 14. |
F. L. Chawarambwa, T. E. Putri, K. Kamataki, M. Shiratani, K. Koga, N. Itagaki, D. Nakamura, Synthesis of Yb3+/Ho3+ co-doped Y2O3 nanoparticles and its application to dye sensitized solar cells, J. Mol. Struct., 10.1016/j.molstruc.2020.129479, 129479, 2020.10. |
| 15. |
R. Narishige, K. Kaneshima, D. Yamashita, K. Kamataki, K. Koga, M. Shiratani, N. Itagaki, Impact of surface morphologies of substrates on the epitaxial growth of magnetron sputtered (ZnO)x(InN)1-x films, Jpn. J. Appl. Phys., 10.35848/1347-4065/abba0c, 60, SA, SAAB02, 2020.10. |
| 16. |
I. Tamošiūnė, D. Gelvonauskienė, P. Haimi, V. Mildažienė, K. Koga, M. Shiratani, D. Baniulis, Cold plasma treatment of sunflower seeds modulates plant-associated microbiome and stimulates root and lateral organ growth, Front. Plant Sci., 10.3389/fpls.2020.568924, 11, 1347, 2020.08. |
| 17. |
S. Nunomura, I. Sakata, H. Sakakita, K. Koga, M. Shiratani, Real-time monitoring of surface passivationof crystalline silicon during growth of amorphous and epitaxial silicon layer, J. Appl. Phys., 10.1063/5.0011563, 128, 3, 2020.07. |
| 18. |
I. Tamošiūnė, D. Gelvonauskienė, L. Ragauskaitė, K. Koga, M. Shiratani, D. Baniulis, Cold plasma treatment of Arabidopsis thaliana (L.) seeds modulates plant-associated microbiome composition, Applied Physics Express, 10.35848/1882-0786/ab9712, 13, 076001, 2020.05. |
| 19. |
N. Itagaki, Y. Nakamura, R. Narishige, K. Takeda, K. Kamataki, K. Koga, M. Hori, M. Shiratani, Growth of single crystalline films on lattice-mismatched substrates through 3D to 2D mode transition, Sci. Rep., 10.1038/s41598-020-61596-w, 10, 1, 4669, 2020.03, Regarding crystalline film growth on large lattice-mismatched substrates, there are two primary modes by which thin films grow on a crystal surface or interface. They are Volmer-Weber (VW: island formation) mode and Stranski-Krastanov (SK: layer-plus-island) mode. Since both growth modes end up in the formation of three-dimensional (3D) islands, fabrication of single crystalline films on lattice-mismatched substrates has been challenging. Here, we demonstrate another growth mode, where a buffer layer consisting of 3D islands initially forms and a relaxed two-dimensional (2D) layer subsequently grows on the buffer layer. This 3D-2D mode transition has been realized using impurities. We observed the 3D-2D mode transition for the case of ZnO film growth on 18%-lattice-mismatched sapphire substrates. First, nano-sized 3D islands grow with the help of nitrogen impurities. Then, the islands coalesce to form a 2D layer after cessation of the nitrogen supply, whereupon an increase in the surface energy may provide a driving force for the coalescence. Finally, the films grow in 2D mode, forming atomically flat terraces. We believe that our findings will offer new opportunities for highquality film growth of a wide variety of materials that have no lattice-matched substrates.. |
| 20. |
K. Koga, P. Attri, K. Kamataki, N. Itagaki, M. Shiratani, V. Mildaziene, Impact of radish sprouts seeds coat color on the electron paramagnetic resonance signals after plasma treatment, Jpn. J. Appl. Phys., 10.35848/1347-4065/ab7698, 59, SH, SHHF01, 2020.03, Recently, cold atmospheric plasma (CAP) treatment on seed germination has emerged as a useful technique to increase agriculture production, although, the mechanism of the cold plasma in seed germination is still under investigation. In this work, we studied the role of pigments in the seed coat of radish sprouts on the electron spin resonance (ESR) signals before and after CAP treatment. Radish sprouts seeds having gray color show enhanced ESR signals after the CAP treatment, whereas, no increased ESR signals were observed for brown color seeds of radish sprouts as compared to their respective control seeds. These results reveal that seeds from the same harvest year having different seed coat colors show different responses to the plasma treatment. Although ESR signal intensity can vary with the harvest year, the change in ESR signal intensity after plasma treatment depends on the seed coat color. Independently on the harvest year (2017 and 2018), CAP increased ESR signals stronger in the grey seeds in comparison to the brown ones. The results indicated that seed coat color may be an important variable for understanding differences in the extent of CAP effects on seeds. (C) 2020 The Japan Society of Applied Physics.. |
| 21. |
T. Kawasaki, K. Nishida, G. Uchida, F. Mitsugi, K. Takenaka, K. Koga, Y. Setsuhara, M. Shiratani, Effects of surrounding gas on plasma-induced downward liquid flow, Jpn. J. Appl. Phys., 10.35848/1347-4065/ab71dc, 59, SH, SHHF02, 2020.03, © 2020 The Japan Society of Applied Physics. Understanding the mechanisms behind plasma-induced liquid flow is important for the transport of reactive species in liquid. In this study, we studied the effects of the surrounding gas compositions of a plasma-jet on the plasma-induced downward liquid flow using particle image velocimetry. Nitrogen (N2) and oxygen (O2) mixtures in different mixing ratios were supplied as surrounding gas around a helium (He) plasma jet at a constant flow rate. The results clearly indicated that O2 in the surrounding gas plays a key role in enhancing the downward flow. Increasing the O2 concentration increased the downward flow in the depth direction. An emission spectroscopy analysis suggested that reactive species related to excited atomic O were considered to be important for inducing downward flows. The relationship between the downward flows and oxidation reactions on a liquid target were discussed to determine the reasons responsible for the driving forces.. |
| 22. |
L. D. Fomins, G. Pauzaite, R. Zukiene, V. Mildaziene, K. Koga, M. Shiratani, Relationship between cold plasma treatment-induced changes in radish seed germination and phytohormone balance, Jpn. J. Appl. Phys., 10.7567/1347-4065/ab656c, 59, SH1001, 2020.02. |
| 23. |
R. Zukiene, Z. Nauciene, I. Januskaitiene, G. Pauzaite, V. Mildaziene, K. Koga, M. Shiratani, Dielectric barrier discharge plasma treatment-induced changes in sunflower seed germination, phytohormone balance, and seedling growth, Appl. Phys. Express, 10.7567/1882-0786/ab5491, 12, 12, 126003, 2019.11. |
| 24. |
K. Tanaka, H. Hara, S. Nagaishi, L. Shi, D. Yamashita, K. Kamataki, N. Itagaki, K. Koga, M. Shiratani, Identification and Suppression of Si-H2 Bond Formation at P/I Interface in a-Si:H Films Deposited by SiH4 Plasma CVD, Plasma Fusion Res., 10.1585/pfr.14.4406141, 14, 4406141, 2019.09. |
| 25. |
L. Shi, K. Tanaka, H. Hara, S. Nagaishi, D. Yamashita, K. Kamataki, N. Itagaki, K. Koga, M. Shiratani, Effect of Higher-Order Silane Deposition on Spatial Profile of Si-H2/Si-H Bond Density Ratio of a-Si:H Films, Plasma Fusion Res., 10.1585/pfr.14.4406144, 14, 4406144, 2019.09. |
| 26. |
S. H. Hwang, K. Kamataki, N. Itagaki, K. Koga, M. Shiratani, Effects of Gas Pressure on the Size Distribution and Structure of Carbon Nanoparticles Using Ar + CH4 Multi-Hollow Discharged Plasma Chemical Vapor Deposition, Plasma Fusion Res., 10.1585/pfr.14.4406115, 14, 4406115, 2019.09. |
| 27. |
R. Zhou, K. Kamataki, H. Ohtomo, D. Yamashita, N. Itagaki, K. Koga, M. Shiratani, Spatial-Structure of Fluctuation of Amount of Nanoparticles in Amplitude-Modulated VHF Discharge Reactive Plasma, Plasma Fusion Res., 10.1585/pfr.14.4406120, 14, 4406120, 2019.09. |
| 28. |
Toshiyuki Kawasaki, Fumiaki Mitsugi, Kazunori Koga, Masaharu Shiratani, Local supply of reactive oxygen species into a tissue model by atmospheric-pressure plasma-jet exposure, Journal of Applied Physics, 10.1063/1.5091740, 125, 213303, 2019.06, © 2019 Author(s). The supply of reactive oxygen species (ROSs) into a tissue by plasmas must be controlled for the safe and effective use of plasma technologies in biomedical applications. In this study, the two-dimensional distributions of ROSs after passing through an agarose tissue model by the plasma-jet exposures were visualized using a KI-starch gel reagent to evaluate the local ROS supply. Partial ROS supply on the tissue model surface induced the local ROS supply in a pointlike shape just under the plasma-exposed spot. The O3-containing gas exposure without direct plasma contact could not induce the local ROS supply. Therefore, the local ROS supply was assumed to be induced by plasma-specific effects. However, the results also indicated that the plasma jet coming in direct contact with the tissue model surface did not necessarily induce the local ROS supply. The effects of the tissue model thickness on the local ROS supply were also studied; the local ROS supply could penetrate to a depth of 2 mm in the tissue model under the given experimental conditions.. |
| 29. |
T. Iwase, Y. Kamaji, S. Y. Kang, K. Koga, N. Kuboi, M. Nakamura, N. Negishi, T. Nozaki, S. Nunomura, D. Ogawa, M. Omura, T. Shimizu, K. Shinoda, Y. Sonoda, H. Suzuki, K. Takahashi, T. Tsutsumi, K. Yoshikawa, T. Ishijima, K. Ishikawa, Progress and perspectives in dry processes for emerging multidisciplinary applications: how can we improve our use of dry processes?, Jpn. J. Appl. Phys. , 10.7567/1347-4065/ab163a, 58, SE0803 , 2019.06. |
| 30. |
Taku Iwase, Yoshito Kamaji, Song Yun Kang, Kazunori Koga, Nobuyuki Kuboi, Moritaka Nakamura, Nobuyuki Negishi, Tomohiro Nozaki, Shota Nunomura, Daisuke Ogawa, Mitsuhiro Omura, Tetsuji Shimizu, Kazunori Shinoda, Yasushi Sonoda, Haruka Suzuki, Kazuo Takahashi, Takayoshi Tsutsumi, Kenichi Yoshikawa, Tatsuo Ishijima, Kenji Ishikawa, Progress and perspectives in dry processes for nanoscale feature fabrication: toward intelligent processes and virtual product development, Japanese Journal of Physics, Vol. 58, pp. SE0804(21pp), 2019.05. |
| 31. |
Sputter Epitaxy of (ZnO)x(InN)1-x films on Lattice-mismatched Sapphire Substrate
We have recently developed a novel semiconductor, (ZnO)x(InN)1-x (abbreviated to ZION). In this study, we have succeeded in direct epitaxial growth of ZION films on 19?21%-lattice-mismatched c-plane sapphire by radio-frequency (RF) magnetron sputtering. X-ray diffraction analysis showed that there is no epitaxial relationship between ZION films fabricated at room-temperature (RT) and the sapphire substrates, while the films fabricated at 450oC grow epitaxially on the sapphire substrates. From the analysis of time evolution of the surface morphology, the process for the epitaxial growth of ZION on sapphire is found to consist of three stages. They are (i) initial nucleation of ZION crystallites with crystal axis aligned to the sapphire substrate, (ii) island growth from the initially formed nuclei and subsequent nucleation (secondary nucleation) of ZION crystallites, and (iii) lateral growth of ZION islands originated from initially formed nuclei. On the other hand, non-epitaxial ZION films fabricated at RT just grow in 3D mode. From these results, we conclude that the substrate temperature is the key to control of nucleation and subsequent epitaxial growth of ZION films on the lattice-mismatched substrate.. |
| 32. |
Effects of nitrogen impurity on zno crystal growth on Si substrates
Effects of nitrogen impurity on ZnO crystal growth on Si substrates have been investigated. The quantitative analysis on the surface morphology deriving height-height correlation function indicates that adsorbed nitrogen atoms suppress the secondary nucleation and enhance adatom migration. The resultant films have smooth surface as well as large grain size up to 24 nm even for small thickness of 10 nm. ZnO films fabricated by using such films as buffer layers possess high crystal quality, where the full width at half maximum of (002) rocking curve is 0.68°, one-fourth of that for films fabricated without nitrogen.. |
| 33. |
Room-temperature fabrication of amorphous In2O3:Sn films with high electron mobility via nitrogen mediated amorphization. |
| 34. |
Spatial correlation between density fluctuations of high energy electrons and nanoparticles in amplitude modulated capactively coupled plasma. |
| 35. |
Photoluminescence of (ZnO)0.82(InN)0.18 films -Incident light angle dependence-
We have fabricated a new semiconducting material, (ZnO)x(InN)1-x (called ZION hereafter), which is a pseudo-binary alloy of wurtzite ZnO (band gap: 3.4 eV) and wurtzite InN (band gap: 0.7 eV). We have succeeded in fabricating epitaxial (ZnO)0.82(InN)0.18 films on ZnO templates by RF magnetron sputtering. XRD measurements show that the full width at half maximum of the rocking curves from (101) plane and (002) plane are significantly small of 0.11 ? and 0.16 ?, respectively, indicating good in-plane and out-of-plane crystal alignment. High crystal quality of the films was also proved by deducing the defect density from XRD analysis showing that the edge type dislocation density is low of 8.2×108 cm-2. Furthermore, we observed room temperature photoluminescence from ZION films as a parameter of incident angle of He-Cd laser light. The results indicate that an emission peak of 2.79 eV is originated from ZION.. |
| 36. |
Effects of sputtering pressure on (ZnO)x(InN)1-x crystal film growth at 450?C
We studied effects of sputtering pressure on growth of (ZnO)x(InN)1-x crystal films deposited at 450°C by rf magnetron sputtering. Epitaxial growth of (ZnO)x(InN)1-x films was realized on single-crystalline ZnO template. X-ray diffraction measurements show that full width at half maximum of the rocking curves from the (101) plane of the films reaches minimum value of 0.11? at 0.5 Pa. The sputtering gas pressure is a key tuning knob for controlling the crystal quality of ZION films.. |
| 37. |
Cross correlation analysis of fluctuation of interactions between nanoparticles and low pressure reactive plasmas
We analyzed fluctuations of interactions between low pressure reactive plasmas and nanoparticles formed in the plasmas, to shed light on origins of fluctuations of interactions and to control fluctuations in plasma processes. Spatiotemporal fluctuations of nanoparticle density develop not only in a linear way but also in a nonlinear way. The results suggest nonlinear interactions potentially induce spatial and temporal process fluctuations.. |
| 38. |
The effect of the H2/(H2 + Ar) flow-rate ratio on hydrogenated amorphous carbon films grown using Ar/H2/C7H8 plasma chemical vapor deposition
© 2018 Elsevier B.V. To produce hydrogenated amorphous carbon (a-C:H) films with high mass density at a high deposition rate and low substrate bias voltage, we deposited these films on a Si substrate by plasma chemical vapor deposition, using toluene as a source compound and varying the gas flow-rate ratio of H2/(H2 + Ar). By decreasing the gas flow-rate ratio from 55% to 11%, the hydrogen content in the films decreased, and the density of sp3 carbon atoms in the films increased, whereas their surface roughness increased. At the gas flow-rate ratio of 11%, we produced a-C:H films with a high bulk density of 1830 kg/m3 at a high deposition rate of 81.1 nm/min.. |
| 39. |
T. Kojima, S. Toko, K. Tanaka, H. Seo, N. Itagaki, K. Koga, M. Shiratani, Effects of gas velocity on deposition rate and amount of cluster incorporation into a-Si:H films fabricated by SiH4 plasma chemical vapor deposition, Plasma Fusion Res., 10.1585/pfr.13.1406082, 13, 1406082, 2018.06. |
| 40. |
S. Toko, R. Katayama, K. Koga, E. Leal-Quiros, M. Shiratani, Dependence of CO2 Conversion to CH4 on CO2 Flow Rate in Helicon Discharge Plasma, Sci. Adv. Mater., 10.1166/sam.2018.3141, 10, 5, 655-659, 2018.05. |
| 41. |
Catalytic enhancement of polymer counter electrode in dye-sensitized solar cells
A counter electrode of dye-sensitized solar cells plays a significant role in the reduction of tri-iodide with electrolyte as a catalyst. Thus, the counter electrode of dye-sensitized solar cells is an important component, which often limits the cell performance. Some materials such as carbon, graphene, carbon nano-tube, transition metal and compounds, and polymer have been investigated as counter electrode materials. However, Pt is still the dominant counter electrode material despite its high cost. This work focused on a low-cost polymer as a counter electrode material of dye-sensitized solar cells. Poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) was applied for the counter electrode. As similar to previous studies on PEDOT:PSS counter electrode, initial photovoltaic performance of dye-sensitized solar cells based on PEDOT:PSS counter electrode was lower than that of Pt counter electrode. Especially, fill factor of dye-sensitized solar cells was significantly decreased from Pt to PEDOT:PSS counter electrodes. To improve the catalytic properties of polymer counter electrodes, this work introduced nanoparticles into polymer layer. Nanoparticle addition increased the surface area of polymer counter electrode and activated the catalytic reactions. Consequently, we have realized the dye-sensitized solar cells with the polymer nanocomposite counter electrode containing PEDOT:PSS and nanoparticles exhibiting higher efficiency and photocurrent than the dye-sensitized solar cells based on Pt counter electrode.. |
| 42. |
Sota Tanami, Daiki Ichida, Shinji Hashimoto, Hyunwoong Seo, Daisuke Yamashita, Naho Itagaki, Kazunori Koga, Masaharu Shiratani, Low temperature rapid formation of Au-induced crystalline Ge films using sputtering deposition, THIN SOLID FILMS, 10.1016/j.tsf.2017.02.067, 641, 59-64, 2017.11, We report low temperature (100-170 degrees C) and rapid (10 min) formation of crystalline Ge films between Au catalyst film and quartz glass substrate using a radio frequencymagnetron sputtering deposition. The formation rate of crystalline Ge films between Au catalyst film and quartz glass substrate is proportional to the deposition rate of Ge film, namely the flux of Ge atoms. To obtain insights on the formation mechanism of crystalline Ge films, we studied dependence of grain size of Au films on annealing temperature and Au film thickness. CrystallineGe films formed belowAu films have randomcrystalline orientationwith in-plane grain size frombelow1 mu m. Small crystalline grain size of Au films is needed to form rapidly Au induced crystalline Ge films. (C) 2017 Elsevier B.V. All rights reserved.. |
| 43. |
Synthesis of nanoparticles using low temperature plasmas and its application to solar cells
We have succeeded in continuously fabricating size-controlled crystalline silicon nanoparticles by using low temperature plasma. For controlling size and structure, gas pressure and H2 dilution ratio of SiH4 are key parameters. We fabricated Schottky cells using synthesized Si nanoparticles which shows multiple exciton generation for photon energy with 3 times larger than their band gap. We utilized the particles to nanoparticle-sensitized solar cells which show the world best efficiency. Moreover, we found the nanoparticle composite polymer counter electrode is promising to low-cost and high performance solar cells.. |
| 44. |
Susumu Toko, Yoshihiro Torigoe, Kimitaka Keya, Takashi Kojima, Hyunwoong Seo, Naho Itagaki, Kazunori Koga, Masaharu Shiratani, Hysteresis in volume fraction of clusters incorporated into a-Si:H films deposited by SiH 4 plasma chemical vapor deposition, Surface and Coatings Technology, 10.1016/j.surfcoat.2017.01.034, 326, 388-394, 2017.10, © 2017 Elsevier B.V. Suppressing cluster incorporation into hydrogenated amorphous silicon films deposited by SiH4discharge plasma is the key to better film stability, because cluster incorporation contributes significantly to the formation of SiH2bonds which are closely related to light-induced degradation of the films. Here, we report hysteresis in the deposition rate and the volume fraction of clusters incorporated into a-Si:H films deposited by SiH4plasma CVD; the deposition rate and the volume fraction show looping behaviors when sequentially changing the discharge power, because clusters formed in the previous condition tend to remain in plasma and affect significantly the deposition rate and the volume fraction. The hysteresis is also shown as a function of SiH* emission intensity, being proportional to the radical generation rate due to electron impact dissociation of SiH4. By utilizing the hysteresis phenomenon, the volume fraction of clusters in films can be reduced significantly. We propose a model of plasma containing clusters, in which clusters play a key role in the hysteresis, namely the nonlinear behavior of the deposition rate and the volume fraction of clusters in films. Eventually, we deposited a-Si:H films of low cluster incorporation at a high deposition rate of 0.09 nm/s utilizing the hysteresis phenomena.. |
| 45. |
Pankaj Attri, Minsup Kim, Eun Ha Choi, Art E. Cho, Kazunori Koga, Masaharu Shiratani, Impact of an ionic liquid on protein thermodynamics in the presence of cold atmospheric plasma and gamma rays, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 10.1039/c7cp04083k, 19, 37, 25277-25288, 2017.10, Cold atmospheric plasma and gamma rays are known to have anticancer properties, even though their specific mechanisms and roles as co-solvents during their action are still not clearly understood. Despite the use of gamma rays in cancer therapy, they have oncogenic potential, whereas this has not been observed for plasma treatment (to date). To gain a better understanding, we studied the action of dielectric barrier discharge (DBD) plasma and gamma rays on the myoglobin protein. We analyzed the secondary structure and thermodynamic properties of myoglobin after both treatments. In addition, in the last few years, ammonium ionic liquids (ILs) have revealed their important role in protein folding as co-solvents. In this work, we treated the protein with ammonium ILs such as triethylammonium methanesulfonate (TEMS) and tetrabutylammonium methanesulfonate (TBMS) and later treated this IL-protein solution with DBD plasma and gamma rays. In this study, we show the chemical and thermal denaturation of the protein after plasma and gamma treatments in the presence and absence of ILs using circular dichroism (CD) and UV-vis spectroscopy. Furthermore, we also show the influence of plasma and gamma rays on the secondary structure of myoglobin in the absence and presence of ILs or ILs + urea using CD. Finally, molecular dynamic simulations were conducted to gain deeper insight into how the ILs behave to protect the protein against the hydrogen peroxide generated by the DBD plasma and gamma rays.. |
| 46. |
Y. Takeiri, T. Morisaki, M. Osakabe, M. Yokoyama, S. Sakakibara, H. Takahashi, Y. Nakamura, T. Oishi, G. Motojima, S. Murakami, K. Ito, A. Ejiri, S. Imagawa, S. Inagaki, M. Isobe, S. Kubo, S. Masamune, T. Mito, I. Murakami, K. Nagaoka, K. Nagasaki, K. Nishimura, M. Sakamoto, R. Sakamoto, T. Shimozuma, K. Shinohara, H. Sugama, K. Y. Watanabe, J. W. Ahn, N. Akata, T. Akiyama, N. Ashikawa, J. Baldzuhn, T. Bando, E. Bernard, F. Castejon, H. Chikaraishi, M. Emoto, T. Evans, N. Ezumi, K. Fujii, H. Funaba, M. Goto, T. Goto, D. Gradic, Y. Gunsu, S. Hamaguchi, H. Hasegawa, Y. Hayashi, C. Hidalgo, T. Higashiguchi, Y. Hirooka, Y. Hishinuma, R. Horiuchi, K. Ichiguchi, K. Ida, T. Ido, H. Igami, K. Ikeda, S. Ishiguro, R. Ishizaki, A. Ishizawa, A. Ito, Y. Ito, A. Iwamoto, S. Kamio, K. Kamiya, O. Kaneko, R. Kanno, H. Kasahara, D. Kato, T. Kato, K. Kawahata, G. Kawamura, M. Kisaki, S. Kitajima, W. H. Ko, M. Kobayashi, S. Kobayashi, T. Kobayashi, K. Koga, A. Kohyama, R. Kumazawa, J. H. Lee, D. Lopez-Bruna, R. Makino, S. Masuzaki, Y. Matsumoto, H. Matsuura, O. Mitarai, H. Miura, J. Miyazawa, N. Mizuguchi, C. Moon, S. Morita, T. Moritaka, K. Mukai, T. Muroga, S. Muto, T. Mutoh, T. Nagasaka, Y. Nagayama, N. Nakajima, Y. Nakamura, H. Nakanishi, H. Nakano, M. Nakata, Y. Narushima, D. Nishijima, A. Nishimura, S. Nishimura, T. Nishitani, M. Nishiura, Y. Nobuta, H. Noto, M. Nunami, T. Obana, K. Ogawa, S. Ohdachi, M. Ohno, N. Ohno, H. Ohtani, M. Okamoto, Y. Oya, T. Ozaki, B. J. Peterson, M. Preynas, S. Sagara, K. Saito, H. Sakaue, A. Sanpei, S. Satake, M. Sato, T. Saze, O. Schmitz, R. Seki, T. Seki, I. Sharov, A. Shimizu, M. Shiratani, M. Shoji, C. Skinner, R. Soga, T. Stange, C. Suzuki, Y. Suzuki, S. Takada, K. Takahata, A. Takayama, S. Takayama, Y. Takemura, Y. Takeuchi, H. Tamura, N. Tamura, H. Tanaka, K. Tanaka, M. Tanaka, T. Tanaka, Y. Tanaka, S. Toda, Y. Todo, K. Toi, M. Toida, M. Tokitani, T. Tokuzawa, H. Tsuchiya, T. Tsujimura, K. Tsumori, S. Usami, J. L. Velasco, H. Wang, T. -H. Watanabe, T. Watanabe, J. Yagi, M. Yajima, H. Yamada, I. Yamada, O. Yamagishi, N. Yamaguchi, Y. Yamamoto, N. Yanagi, R. Yasuhara, E. Yatsuka, N. Yoshida, M. Yoshinuma, S. Yoshimura, Y. Yoshimura, Extension of the operational regime of the LHD towards a deuterium experiment, NUCLEAR FUSION, 10.1088/1741-4326/aa7fc2, 57, 10, 2017.10, As the finalization of a hydrogen experiment towards the deuterium phase, the exploration of the best performance of hydrogen plasma was intensively performed in the large helical device. High ion and electron temperatures, T-i and T-e, of more than 6 keV were simultaneously achieved by superimposing high-power electron cyclotron resonance heating onneutral beam injection (NBI) heated plasma. Although flattening of the ion temperature profile in the core region was observed during the discharges, one could avoid degradation by increasing the electron density. Another key parameter to present plasma performance is an averaged beta value . The high regime around 4% was extended to an order of magnitude lower than the earlier collisional regime. Impurity behaviour in hydrogen discharges with NBI heating was also classified with a wide range of edge plasma parameters. The existence of a no impurity accumulation regime, where the high performance plasma is maintained with high power heating > 10 MW, was identified. Wide parameter scan experiments suggest that the toroidal rotation and the turbulence are the candidates for expelling impurities from the core region.. |
| 47. |
Hyunwoong Seo, Chandu V. V. M. Gopi, Hee-Je Kim, Naho Itagaki, Kazunori Koga, Masaharu Shiratani, Performance enhancement of quantum dot-sensitized solar cells based on polymer nano-composite catalyst, ELECTROCHIMICA ACTA, 10.1016/j.electacta.2017.08.030, 249, 337-342, 2017.09, Polymer nano-composite composed of poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) and TiO2 nano-particles was deposited on fluorine-doped tin oxide substrate and applied as an alternative to Au counter electrode of quantum dot-sensitized solar cell (QDSC). It became surface-richer with the increase in nano-particle amount so that catalytic reaction was increased by widened catalytic interface. Electrochemical impedance spectroscopy and cyclic voltammetry clearly demonstrated the enhancement of polymer nano-composite counter electrode. A QDSC based on polymer nano-composite counter electrode showed 0.56 V of V-OC, 12.24 mA cm(-2) of J(SC), 0.57 of FF, and 3.87% of efficiency and this photovoltaic performance was higher than that of QDSC based on Au counter electrode (3.75%). (C) 2017 Elsevier Ltd. All rights reserved.. |
| 48. |
Pankaj Attri, Minsup Kim, Thapanut Sarinont, Eun Ha Choi, Hyunwoong Seo, Art E. Cho, Kazunori Koga, Masaharu Shiratani, The protective action of osmolytes on the deleterious effects of gamma rays and atmospheric pressure plasma on protein conformational changes, SCIENTIFIC REPORTS, 10.1038/s41598-017-08643-1, 7, 8698, 2017.08, Both gamma rays and atmospheric pressure plasma are known to have anticancer properties. While their mechanism actions are still not clear, in some contexts they work in similar manner, while in other contexts they work differently. So to understand these relationships, we have studied Myoglobin protein after the treatment of gamma rays and dielectric barrier discharge (DBD) plasma, and analyzed the changes in thermodynamic properties and changes in the secondary structure of protein after both treatments. The thermodynamic properties were analyzed using chemical and thermal denaturation after both treatments. We have also studied the action of gamma rays and DBD plasma on myoglobin in the presence of osmolytes, such as sorbitol and trehalose. For deep understanding of the action of gamma rays and DBD plasma, we have analyzed the reactive species generated by them in buffer at all treatment conditions. Finally, we have used molecular dynamic simulation to understand the hydrogen peroxide action on myoglobin with or without osmolytes, to gain deeper insight into how the osmolytes can protect the protein structure from the reactive species generated by gamma rays and DBD plasma.. |
| 49. |
K. Koga, H. Seo, A. Tanaka, N. Itagaki, M. Shiratani, Synthesis of Nanoparticles using Low Temperature Plasmas and Its Application to Solar Cells and Tracers in Living Body , ECS Transactions, 10.1149/07703.0017ecst, 77, 3, 17-24, 2017.05. |
| 50. |
Synthesis of nanoparticles using low temperature plasmas and its application to solar cells. |
| 51. |
Koichi Matsushima, Tomoaki Ide, Keigo Takeda, Masaru Hori, Daisuke Yamashita, Hyunwoong Seo, Kazunori Koga, Masaharu Shiratani, Naho Itagaki, Densities and Surface Reaction Probabilities of Oxygen and Nitrogen Atoms During Sputter Deposition of ZnInON on ZnO, IEEE TRANSACTIONS ON PLASMA SCIENCE, 10.1109/TPS.2016.2632124, 45, 2, 323-327, 2017.03, We report densities and surface reaction probabilities of O and N atoms during sputter deposition of ZnInON films on ZnO templates, measured via vacuum ultraviolet absorption spectroscopy. O density is almost constant of 4.5 x 10(11) cm(-3) irrespective of O-2 gas flow rate, whereas N density increases sharply from 2.7x10(11) cm(-3) for O-2 gas sccm to 7.7 x 10(11) cm(-3) for 0.6 sccm and it increases gradually 10(11) cm(-3) for 5 sccm. The surface reaction probability beta(O) of O atoms on ZnInON increases significantly from 0.022 to 0.404 with increasing O-2 gas flow rate from 0 to 5 sccm, whereas beta(N) of N atoms on ZnInON decreases slightly from 0.018 to 0.006. The stoichiometric chemical compositional ratio of ZnInON films with [Zn]/([Zn] + [In]) = [O]/([O] + [N]) = 94% is obtained at beta(O) = 0.404 of O atoms. This stoichiometric compositional ZnInON films grow coherently on ZnO templates, while nonstoichiometric films do not. The stoichiometric chemical composition is the key to coherent growth of ZnInON films.. |
| 52. |
T. Sarinont, R. Katayama, Y. Wada, K. Koga, M. Shiratani, Plant Growth Enhancement of Seeds Immersed in Plasma Activated Water, MRS Adv., 10.1557/adv.2017.178, 2, 18, 995-1000, 2017.02. |
| 53. |
T. Sarinont, Y. Wada, K. Koga, M. Shiratani, Response of Silkworm Larvae to Atmospheric Pressure Non-thermal Plasma Irradiation, Plasma Medicine, 10.1615/PlasmaMed.2017019137 , 6, 3-4, 2017.01. |
| 54. |
Influence of plasma irradiation on silkworm
© 2017 by Begell House, Inc. Silkworms have recently been proposed as an animal model for safety testing in basic research. We propose using silkworms for in vivo trials of direct plasma treatment. In this study, the influence of plasma irradiation on silkworms was investigated using a non-thermal atmospheric pressure plasma. Silkworm survival rate decreased with increasing low-frequency voltage and plasma irradiation period. Further investigation of the plasma-generated agents (oxygen related radicals, UV light, and charged particles), revealed that the contribution of charged particles significantly increases silkworm mortality.. |
| 55. |
K. Iwasaki, K. Matsushima, D. Yamashita, H. Seo, K. Koga, M. Shiratani, N. Itagaki , Effects of sputtering gas pressure dependence of surface morphology of ZnO films fabricated via nitrogen mediated crystallization, MRS Adv., 10.1557/adv.2016.617, 2, 5, 265-270, 2016.12. |
| 56. |
K. Matsushima, K. Iwasaki, N. Miyahara, D. Yamashita, H. Seo, K. Koga, M. Shiratani, N. Itagaki, Blue Photoluminescence of (ZnO)0.92(InN)0.08, MRS Adv., 10.1557/adv.2016.625, 2, 5, 277-282, 2016.12. |
| 57. |
Giichiro Uchida, Atsushi Nakajima, Taiki Ito, Kosuke Takenaka, Toshiyuki Kawasaki, Kazunori Koga, Masaharu Shiratani, Yuichi Setsuhara, Effects of nonthermal plasma jet irradiation on the selective production of H2O2 and NO2- in liquid water, JOURNAL OF APPLIED PHYSICS, 10.1063/1.4968568, 120, 20, 203302-1 - 203302-9, 2016.11, We present the effects of the application of a nonthermal plasma jet to a liquid surface on H2O2 and NO2- generation in the liquid. Two distinct plasma irradiation conditions, with plasma contact and with no observable plasma contact with the liquid surface, were precisely compared. When the plasma was made to touch the liquid surface, the H2O2 concentration of the plasma-treated water was much higher than the NO2- concentration. In contrast, when no observable contact of the plasma with the liquid surface occurred, the ratio of the NO2- to H2O2 concentration became over 1 and NO2- became more dominant than H2O2 in the plasma-treated water. Our experiments clearly show that reactive oxygen and nitrogen species can be selectively produced in liquid using appropriate plasma-irradiation conditions of the liquid surface. The ratio of NO2- to H2O2 was controlled within a wide range of 0.02-1.2 simply by changing the plasma-irradiation distance from the liquid surface. Published by AIP Publishing.. |
| 58. |
M. Shiratani, M. Soejima, H. Seo, N. Itagaki, K. Koga , Fluctuation of Position and Energy of a Fine Particle in Plasma Nanofabrication, Materials Science Forum, 10.4028/www.scientific.net/MSF.879.1772, 879, 1772-1777 , 2016.11. |
| 59. |
Susumu Toko, Yoshinori Kanemitsu, Hyunwoong Seo, Naho Itagaki, Kazunori Koga, Masaharu Shiratani, Optical Bandgap Energy of Si Nanoparticle Composite Films Deposited by a Multi-Hollow Discharge Plasma Chemical Vapor Deposition Method, JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY, 10.1166/jnn.2016.13233, 16, 10, 10753-10757, 2016.10, Semiconductor nanoparticles have significant potential for optoelectronic applications such as solar cells and light-emitting diodes. We are developing semiconductor nanoparticle composite films with a wide bandgap to be used as the window layer of solar cells because the bandgap energy increases with a decrease in the size of particles in the nanometer size range due to the quantum size effect. A multi-hollow discharge plasma chemical vapor deposition (CVD) method was used to fabricate Si nanoparticle composite films and control the volume fraction of nanoparticles in the films. The bandgap energy was increased from 2 eV for a crystalline volume fraction X-c of 0.2 to 2.5 eV for X-c = 0.6 and then decreased to 1.1 eV for X-c = 1. The photo and dark conductivity of films indicate high stability against light soaking. Si nanoparticle composite films with bandgap energies above 2.2 eV are thus promising candidate materials for the window layer of thin-film solar cells.. |
| 60. |
Thapanut Sarinont, Takaaki Amano, Pankaj Attri, Kazunori Koga, Nobuya Hayashi, Masaharu Shiratani, Effects of plasma irradiation using various feeding gases on growth of Raphanus sativus L., ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS, 10.1016/j.abb.2016.03.024, 605, 129-140, 2016.09, In this work, we have studied the action of dielectric barrier discharge (DBD) plasma irradiation using various feeding gases on seeds of Raphanus sativus L. and analysis their growth. Our experimental data shows that Air, O-2, and NO(10%)+N-2 feeding gases plasma irradiation enhanced plant growth, whereas N-2, He and Ar feeding gases plasma irradiation had little influence on plant growth. Moreover, humid air plasma irradiation was more effective in growth enhancement than dry one. More than 2.3 times faster growth was observed by 3 min air plasma irradiation with 40-90% relative humidity. The reactive species generated by plasma in gas phase were detected using optical emission spectroscopy and in liquid phase by electron spin resonance (ESR) spectroscopy. We concluded that OH and O radicals were key species for plant growth enhancement. (C) 2016 Elsevier Inc. All rights reserved.. |
| 61. |
Hyunwoong Seo, Min-Kyu Son, Shinji Hashimoto, Toshiyuki Takasaki, Naho Itagaki, Kazunori Koga, Masaharu Shiratani, Surface Modification of Polymer Counter Electrode for Low Cost Dye-sensitized Solar Cells, ELECTROCHIMICA ACTA, 10.1016/j.electacta.2016.06.020, 210, 880-887, 2016.08, Poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) was already used as a counter electrode material of dye-sensitized solar cells (DSCs) in other previous researches but its low catalytic activity has been a sticking point. Here we report the catalytic activation of PEDOT:PSS counter electrode by the surface modification using nano-particles. Nano-particle addition contributes to widening catalytic interface and improving catalytic characteristics of PEDOT:PSS counter electrode. However, only a few materials are applicable although various nano-particle materials were applied for the counter electrode of DSC. Catalytic characteristics of PEDOT:PSS counter electrodes with nano-particles are analyzed by cyclic voltammetry and electrochemical impedance spectroscopy. Finally, a DSC based on catalytically enhanced polymer counter electrode achieves 0.71 V of V-OC, 12.60 mA cm(-2) of J(SC), 0.75 of FF, and 6.65% of efficiency, and it is higher than 5.60% of efficiency of a DSC based on conventional Pt counter electrode. (C) 2016 Elsevier Ltd. All rights reserved.. |
| 62. |
Hyunwoong Seo, Sang-Hun Nam, Naho Itagaki, Kazunori Koga, Masaharu Shiratani, Jin-Hyo Boo, Effect of Sulfur Doped TiO2 on Photovoltaic Properties of Dye-Sensitized Solar Cells, ELECTRONIC MATERIALS LETTERS, 10.1007/s13391-016-4018-8, 12, 4, 530-536, 2016.07, In a dye-sensitized solar cell (DSC), a nano-porous semiconductor layer plays an important role in the performance. It determines open-circuit voltage and it affects the dye adsorption capacity and charge transfer, which are closely associated with photocurrent and overall performance. TiO2 is the most proper material for nano-porous layer since the first development of DSCs. This work focuses on the enhancement of TiO2 by doping. Sulfur (S) doping enhances charge transfer and the photo-conversion of TiO2. Therefore, the increase in photocurrent and efficiency is expected by S doping. S is doped into TiO2 by hydrolysis method. The amount of S is varied and their photo-responses are verified. The most effective S doped TiO2 is applied to DSCs. Overall performance of DSC is enhanced by the addition of S doped TiO2. Especially, the photocurrent is much increased by the improvement on charge transfer, electron lifetime, and photo-conversion. The photovoltaic properties of DSCs are investigated with various ratios of undoped and S doped TiO2. Finally, a DSC based on undoped and S doped TiO2 ratio of 1:1 has the highest efficiency, better than that of a standard DSC based on undoped TiO2.. |
| 63. |
Kimitaka Keya, Takashi Kojima, Yoshihiro Torigoe, Susumu Toko, Daisuke Yamashita, Hyunwoong Seo, Naho Itagaki, Kazunori Koga, Masaharu Shiratani, Correlation between SiH2/SiH and light-induced degradation of p-i-n hydrogenated amorphous silicon solar cells, JAPANESE JOURNAL OF APPLIED PHYSICS, 10.7567/JJAP.55.07LE03, 55, 7, 07LE03, 2016.07, We have measured the hydrogen content ratio ISiH2/ISiH associated with Si-H-2 and Si-H bonds in p-i-n (PIN) a-Si:H solar cells by Raman spectroscopy. With decreasing ISiH2/ISiH, the efficiency, short-circuit current density, open-circuit voltage, and fill factor of PIN a-Si: H solar cells after light soaking tend to increase. Namely, ISiH2/ISiH correlates well with light-induced degradation of the cells. While a single I-layer has a low ISiH2/ISiH of 0.03-0.09, a PIN cell has ISiH2/ISiH = 0.18 because many Si-H-2 bonds exist in the P-layer and at the P/I interface of the PIN solar cells. To realize PIN solar cells with higher stability, we must suppress Si-H-2 bond formation in the P-layer and at the P/I interface. (C) 2016 The Japan Society of Applied Physics. |
| 64. |
Toshiyuki Kawasaki, Akihiro Sato, Shota Kusumegi, Akihiro Kudo, Tomohiro Sakanoshita, Takuya Tsurumaru, Giichiro Uchida, Kazunori Koga, Masaharu Shiratani, Two-dimensional concentration distribution of reactive oxygen species transported through a tissue phantom by atmospheric-pressure plasma-jet irradiation, APPLIED PHYSICS EXPRESS, 10.7567/APEX.9.076202, 9, 7, 2016.07, The two-dimensional concentration distribution of reactive oxygen species (ROSs) transported through an agarose-film tissue phantom by atmospheric-pressure plasma-jet irradiation is visualized using a KI-starch gel reagent. Oxygen addition to helium enhances ROS transportation through the film. A radial ROS distribution pattern at the plasma-irradiated film surface changes into a doughnut-shaped pattern after passing through the film. The ROS transportation speed is 0.14-0.2mm/min. We suggest that there are two types of ROS transportation pathways in the plasma-irradiated film: linear and circular. The majority of ROSs are transported through the circular pathway. ROS concentration distributions changed markedly with irradiation distance. Diffusive ROS transportation due to a concentration gradient is negligible in plasma-irradiated films. (C) 2016 The Japan Society of Applied Physics. |
| 65. |
Keya Kimitaka, Kojima Takashi, Torigoe Yoshihiro, Toko Susumu, Yamashita Daisuke, Seo Hyunwoong, Itagaki Naho, Koga Kazunori, Shiratani Masaharu, Correlation between SiH, Jpn. J. Appl. Phys., 10.7567/JJAP.55.07LE03, 55, 7, 07LE03, 2016.06, We have measured the hydrogen content ratio ISiH2/ISiHassociated with Si–H2and Si–H bonds in p–i–n (PIN) a-Si:H solar cells by Raman spectroscopy. With decreasing ISiH2/ISiH, the efficiency, short-circuit current density, open-circuit voltage, and fill factor of PIN a-Si:H solar cells after light soaking tend to increase. Namely, ISiH2/ISiHcorrelates well with light-induced degradation of the cells. While a single I-layer has a low ISiH2/ISiHof 0.03–0.09, a PIN cell has ISiH2/ISiH= 0.18 because many Si–H2bonds exist in the P-layer and at the P/I interface of the PIN solar cells. To realize PIN solar cells with higher stability, we must suppress Si–H2bond formation in the P-layer and at the P/I interface.. |
| 66. |
Hyunwoong Seo, Daiki Ichida, Shinji Hashimoto, Naho Itagaki, Kazunori Koga, Masaharu Shiratani, Sang-Hun Nam, Jin-Hyo Boo, Improvement of Charge Transportation in Si Quantum Dot-Sensitized Solar Cells Using Vanadium Doped TiO2, JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY, 10.1166/jnn.2016.12210, 16, 5, 4875-4879, 2016.05, The multiple exciton generation characteristics of quantum dots have been expected to enhance the performance of photochemical solar cells. In previous work, we first introduced Si quantum dot for sensitized solar cells. The Si quantum dots were fabricated by multi-hollow discharge plasma chemical vapor deposition, and were characterized optically and morphologically. The Si quantum dot-sensitized solar cells had poor performance due to significant electron loss by charge recombination. Although the large Si particle size resulted in the exposure of a large TiO2 surface area, there was a limit to ho much the particle size could be decreased due to the reduced absorbance of small particles. Therefore, this work focused on decreasing the internal impedance to improve charge transfer. TiO2 was electronically modified by doping with vanadium, which can improve electron transfer in the TiO2 network, and which is stable in the redox electrolyte. Photogenerated electrons can more easily arrive at the conductive electrode due to the decreased internal impedance. The dark photovoltaic properties confirmed the reduction of charge recombination, and the photon-to-current conversion efficiency reflected the improved electron transfer. Impedance analysis confirmed a decrease in internal impedance and an increased electron lifetime. Consequently, these improvements by vanadium doping enhanced the overall performance of Si quantum dot-sensitized solar cells.. |
| 67. |
Toshiyuki Kawasaki, Shota Kusumegi, Akihiro Kudo, Tomohiro Sakanoshita, Takuya Tsurumaru, Akihiro Sato, Giichiro Uchida, Kazunori Koga, Masaharu Shiratani, Effects of irradiation distance on supply of reactive oxygen species to the bottom of a Petri dish filled with liquid by an atmospheric O-2/He plasma jet, JOURNAL OF APPLIED PHYSICS, 10.1063/1.4948430, 119, 17, 173301, 2016.05, The impact of irradiation distances on plasma jet-induced specific effects on the supply of reactive oxygen species (ROS) to the bottom of a Petri dish filled with liquid was investigated using a KI-starch gel reagent that can be employed as a ROS indicator even in water. O-3 exposure experiments without plasma irradiation were also performed to elucidate the specific effects of the plasma jet. Relative concentrations of ROS transported to the bottom were evaluated using absorbance measurements. The results indicated that ROS supply to the bottom is markedly enhanced by the plasma jet irradiation at shorter irradiation distances, whereas similar results could not be obtained for the O-3 exposure. In these cases, the liquid mixing in the depth direction was also enhanced by the plasma jet irradiation only, and the supply of reactive atomic oxygen to the liquid surface was markedly increased as well. Published by AIP Publishing.. |
| 68. |
M. Shiratani, T. Sarinont, K. Koga and N. Hayashi, R&D status of agricultural applications of high voltage and plasma in Japan, Proc. Workshop on Application of Advanced Plasma Technologies in CE Agriculture, 29-30, 2016.04. |
| 69. |
H. Seo, G. Uchida, N. Itagaki, K. Koga, and M. Shiratani , Quantum Characterization of Si Nano-Particles Fabricated by Multi-Hollow Discharge Plasma Chemical Vapor Deposition, Sci. Adv. Mater., 10.1166/sam.2016.2520, 8, 3, 636-639, 2016.03. |
| 70. |
Hyunwoong Seo, Min-Kyu Son, Naho Itagaki, Kazunori Koga, Masaharu Shiratani, Polymer counter electrode of poly(3,4-ethylenedioxythiophene):Poly(4-styrenesulfonate) containing TiO2 nano-particles for dye-sensitized solar cells, JOURNAL OF POWER SOURCES, 10.1016/j.jpowsour.2015.12.112, 307, 25-30, 2016.03, A counter electrode of dye-sensitized solar cells (DSC) is an important component, which often limits the cell performance. Here we report a low-cost and high-performance polymer counter electrode of poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) containing TiO2 nano-particles for dye-sensitized solar cells. Catalytic characteristics of the counter electrode are significantly improved by adding TiO2 nano-particles to PEDOT:PSS. This improvement is attributed to catalytic activation due to an increase in the surface area of the counter electrode and an increase in conductivity of PEDOT:PSS due to its structural change. A dye-sensitized solar cell using the polymer counter electrode shows 8.27% of efficiency and 16.39 mA cm(-2) of short circuit current density, higher than 7.59% of efficiency and 14.75 mA cm(-2) of short circuit current density of a cell with the conventional Pt counter electrode. (C) 2015 Elsevier B.V. All rights reserved.. |
| 71. |
Hyunwoong Seo, Giichiro Uchida, Naho Itagaki, Kazunori Koga, Masaharu Shiratani, Quantum Characterization of Si Nano-Particles Fabricated by Multi-Hollow Discharge Plasma Chemical Vapor Deposition, SCIENCE OF ADVANCED MATERIALS, 10.1166/sam.2016.2520, 8, 3, 636-639, 2016.03, Si is currently the most widely used material in the photovoltaics. Since the first development of Si photovoltaics, various types of Si solar cells, such as single-crystal and multicrystalline, amorphous and thin film, have been developed and commercialized. The present work focused on Si quantum dots as another route to Si photovoltaics. To apply Si quantum dots to photovoltaic devices, the quantum characteristics of Si nano particles should be verified, and so 4 nm crystalline Si nano-particles were fabricated by multi-hollow discharge plasma chemical vapor deposition. The size and distribution of these particles were determined by transmission electron microscopy and compared against theoretically calculated values. These particles were applied to the fabrication of a Schottky cell and the quantum efficiency of the Si quantum dot layer was measured as a function of the incident photon energy. The quantum efficiency was found to exceed 100% and so multiple exciton generation from the Si quantum dots was clearly realized.. |
| 72. |
K. Matsushima, T. Ide, D. Yamashita, H. Seo, K. Koga, M. Shiratani, N. Itagaki, Room Temperature Fabrication of (ZnO)x(InN)1-x films with Step-Terrace Structure by RF Magnetron Sputtering, MRS Advances, 10.1557/adv.2015.59, 1, 2, 115-119, 2016.01. |
| 73. |
Susumu Toko, Yoshihiro Torigoe, Kimitaka Keya, Hyunwoong Seo, Naho Itagaki, Kazunori Koga, Masaharu Shiratani, Effects of gas flow rate on deposition rate and number of Si clusters incorporated into a-Si:H films, JAPANESE JOURNAL OF APPLIED PHYSICS, 10.7567/JJAP.55.01AA19, 55, 1, 01AA19, 2016.01, The suppression of cluster incorporation into a-Si: H films is the key to better film stability, because incorporated clusters contribute to the formation of SiH2 bonds and hence lead to light-induced degradation of the films. To deposit stable a-Si: H solar cells at a high deposition rate (DR), we studied the effects of the gas flow rate on DR and the number of Si clusters incorporated into a-Si: H films with discharge power as a parameter, using a multihollow discharge-plasma chemical vapor deposition method. We succeeded in depositing high-quality a-Si: H films with the incorporation of few clusters at DR of 0.1nm/s. We also found that, under a low gas flow rate and a high discharge power, high-density clusters exist in plasma and hence DR is reduced as a result of radical loss to the clusters. (C) 2016 The Japan Society of Applied Physics. |
| 74. |
Xiao Dong, Kazunori Koga, Daisuke Yamashita, Hyunwoong Seo, Naho Itagaki, Masaharu Shiratani, Yuichi Setsuhara, Makoto Sekine, Masaru Hori, Effects of deposition rate and ion bombardment on properties of a-C:H films deposited by H-assisted plasma CVD method, JAPANESE JOURNAL OF APPLIED PHYSICS, 10.7567/JJAP.55.01AA11, 55, 1, 01AA11, 2016.01, In our previous study, we realized conformal, subconformal, and anisotropic deposition profiles of hydrogenated amorphous carbon (a-C:H) films formed on trench substrates by plasma CVD using toluene. To obtain information on the film structures, we investigated the effects of deposition rate and ion bombardment on hydrogen bonding configurations and hydrogen content in the a-C: H films deposited by plasma CVD using toluene. The structure of a-C: H films transforms from polymer-like a-C:H (PLCH) for the ion energy |
| 75. |
T. Amano, T. Sarinont, K. Koga, M. Hirata, A. Tanaka, M. Shiratani, Production of In, Au, and Pt nanoparticles by discharge plasmas in water for assessment of their bio-compatibility and toxicity, MRS Adv., 10.1557/adv.2016.41, 1, 18, 1301-1306, 2016.01. |
| 76. |
M. Shiratani, T. Sarinont, T. Amano, N. Hayashi, K. Koga, Plant Growth Response to Atmospheric Air Plasma Treatments of Seeds of 5 Plant Species, MRS Adv., 10.1557/adv.2016.37, 1, 18, 1265-1269, 2016.01. |
| 77. |
Kazunori Koga, Sarinont Thapanut, Takaaki Amano, Hyunwoong Seo, Naho Itagaki, Nobuya Hayashi, Masaharu Shiratani, Simple method of improving harvest by nonthermal air plasma irradiation of seeds of Arabidopsis thaliana (L.), APPLIED PHYSICS EXPRESS, 10.7567/APEX.9.016201, 9, 1, 016201, 2016.01, We have studied the effects of air nonthermal plasma irradiation of seeds of Arabidopsis thaliana (L.) on their growth from the beginning of cultivation to their harvest. Three minute plasma irradiation of dry seeds resulted in growth acceleration in all the growth stages. Compared with the control, the plasma irradiation led to an 11% shorter harvest period, a 56% increase in total seed weight, a 12% increase in each seed weight, and a 39% increase in seed number. (C) 2016 The Japan Society of Applied Physics. |
| 78. |
Pankaj Attri, Thapanut Sarinont, Minsup Kim, Takaaki Amano, Kazunori Koga, Art E. Cho, Eun Ha Choi, Masaharu Shiratani, Influence of ionic liquid and ionic salt on protein against the reactive species generated using dielectric barrier discharge plasma, SCIENTIFIC REPORTS, 10.1038/srep17781, 5, 17781 , 2015.12, The presence of salts in biological solution can affect the activity of the reactive species (RS) generated by plasma, and so they can also have an influence on the plasma-induced sterilization. In this work, we assess the influence that diethylammonium dihydrogen phosphate (DEAP), an ionic liquid (IL), and sodium chloride (NaCl), an ionic salt (IS), have on the structural changes in hemoglobin (Hb) in the presence of RS generated using dielectric barrier discharge (DBD) plasma in the presence of various gases [O-2, N-2, Ar, He, NO (10%) + N-2 and Air]. We carry out fluorescence spectroscopy to verify the generation of (OH)-O-center dot with or without the presence of DEAP IL and IS, and we use electron spin resonance (ESR) to check the generation of H-center dot and (OH)-O-center dot. In addition, we verified the structural changes in the Hb structure after treatment with DBD in presence and absence of IL and IS. We then assessed the structural stability of the Hb in the presence of IL and IS by using molecular dynamic (MD) simulations. Our results indicate that the IL has a strong effect on the conservation of the Hb structure relative to that of IS against RS generated by plasma.. |
| 79. |
Giichiro Uchida, Atsushi Nakajima, Kosuke Takenaka, Kazunori Koga, Masaharu Shiratani, Yuichi Setsuhara, Gas Flow Rate Dependence of the Discharge Characteristics of a Plasma Jet Impinging Onto the Liquid Surface, IEEE TRANSACTIONS ON PLASMA SCIENCE, 10.1109/TPS.2015.2488619, 43, 12, 4081-4087, 2015.12, We present here an analysis of the discharge characteristics near the liquid surface in the plasma jet operated at a He gas flow rate of 1.5-10 slm. The plasma diameter on the liquid surface increases with an increase in He gas flow rate, which results in an increase in the total amount of charge particles transferred from the plasma to the liquid. We also analyzed the gas flow patterns using a Schlieren gas flow imaging system. The diameter of the laminar flow and the gas flow distance along the liquid surface increase with an increase in He gas flow rate, which well explains the increase in the plasma diameter on the liquid surface. Our experiments clearly demonstrate that high gas flow rate realizes the large reaction area between the water molecule and the plasma in the plasma jet system.. |
| 80. |
Takaaki Amano, Thapanut Sarinont, Kazunori Koga, Miyuki Hirata, Akiyo Tanaka, Masaharu Shiratani, Synthesis of Indium-Containing Nanoparticles in Aqueous Suspension Using Plasmas in Water for Evaluating Their Kinetics in Living Body, JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY, 10.1166/jnn.2015.11427, 15, 11, 9298-9302, 2015.11, Nanoparticles have great potential for medical applications such as cancer therapy, whereas their toxic effects on human body are pointed out. To study kinetics and toxicity of nanoparticles in living body, we synthesized indium-containing nanoparticles in aqueous suspension using pulsed electrical discharge plasmas in water, because no indium compounds exist in the living body in the normal situation and hence indium-containing nanoparticles are useful tracer materials for analyzing kinetics of nanoparticles in living body. The mean size of synthesized primary nanoparticles is 7 nm, whereas the mean size of secondary nanoparticles is 315 nm. EDX and XRD analysis reveal that nanoparticles are indium crystalline and indium hydroxide crystalline with the mass ratio of 8:2. Preliminary subcutaneous administration of nanoparticles to mice shows that indium is transported from subcutaneous to blood. These results show that synthesized indium-containing nanoparticles are useful for analyzing kinetics of nanoparticles in living body.. |
| 81. |
Hyunwoong Seo, Shinji Hashimoto, Daiki Ichida, Naho Itagaki, Kazunori Koga, Masaharu Shiratani, Structural alternation of tandem dye-sensitized solar cells based on mesh-type of counter electrode, ELECTROCHIMICA ACTA, 10.1016/j.electacta.2015.04.105, 179, 206-210, 2015.10, Tandem dye-sensitized solar cells (DSCs) are very effective to improve light absorption characteristics and overall performance. The structure of conventional tandem DSC is an assembly of two independent DSCs. Therefore, additional TiO2 layer, Pt film, and transparent conductive oxide (TCO) electrodes weaken incident light to the bottom cell and complicate the fabrication as compared with standard DSCs. Here, this work proposed the structural alternation of tandem DSC as a solution. Mesh type of counter electrode was inserted between top and bottom cells instead of TCO electrodes. Two photo electrodes shared electrolyte and counter electrode in this structure. High aperture ratio of mesh increased light penetration into bottom cell and led to the performance improvement. Structural alternation also simplified the fabrication. It could be fabricated like standard DSCs. After dye arrangement and TiO2 layer of bottom cell were controlled, the photovoltaic performance of proposed tandem DSC was enhanced and it was higher than conventional tandem DSC. Finally, the long-term stability of proposed tandem DSC was secured by the control of sealing walls. (C) 2015 Elsevier Ltd. All rights reserved.. |
| 82. |
X. Dong, K. Koga, D. Yamashita, H. Seo, N. Itagaki, M. Shiratani, Y. Setsuhara, M. Sekine, M. Hori, Raman Spectroscopy of a-C:H Films Deposited Using Ar + H2+ C7H8 Plasma CVD, Proc. 68th GEC/9th ICRP/33rd SPP, 60, 9, GT1.145, 2015.10. |
| 83. |
T. Takasaki, T. Ide, K. Matsushima, K. Takeda, M. Hori, D. Yamashita, H. Seo, K. Koga, M, Shiratani, N. Itagaki, Measurements of nitrogen atom density in N2/Ar sputtering plasma for fabrication of high-mobility amorphous In2O3:Sn films, Proc. 68th GEC/9th ICRP/33rd SPP, 60, 9, GT1.150, 2015.10. |
| 84. |
K. Matsushima, T. Ide, K. Takeda, M. Hori, D. Yamashita, H. Seo, K. Koga, M, Shiratani, N. Itagaki, Measurements of absolute densities of nitrogen and oxygen atoms in sputtering plasma for fabrication of ZnInON films, Proc. 68th GEC/9th ICRP/33rd SPP, 60, 9, GT1.154, 2015.10. |
| 85. |
T. Ide, K. Matsushima, T. Takasaki, K. Takeda, M. Hori, D. Yamashita, H. Seo, K. Koga, M, Shiratani, N. Itagaki, Measurement of absolute density of N atom in sputtering plasma for epitaxial growth ZnO films via nitrogen mediated crystallization, Proc. 68th GEC/9th ICRP/33rd SPP, 60, 9, GT1.155, 2015.10. |
| 86. |
T. Sarinont, T. Amano, K. Koga, S. Kitazaki, N. Hayashi, M. Shiratani, Effects of Ambient Humidity on Plant Growth Enhancement by Atmospheric Air Plasma Irradiation to Plant Seeds, Proc. 68th GEC/9th ICRP/33rd SPP, 60, 9, LW1.136, 2015.10. |
| 87. |
G. Uchida, A. Nakajima, T. Kawasaki, K. Koga, K. Takenaka, M. Shiratani, Y. Setsuhara, Gas flow rate dependence of the production of reactive oxygen species in liquid by a plasma-jet irradiation, Proc. 68th GEC/9th ICRP/33rd SPP, 60, 9, TF1.2, 2015.10. |
| 88. |
Y. Setsuhara, G. Uchida, A. Nakajima, K. Takenaka, K. Koga, M. Shiratani, Discharge characteristics and hydrodynamics behaviors of atmospheric plasma jets produced in various gas flow patterns, Proc. 68th GEC/9th ICRP/33rd SPP, 60, 9, LW1.58, 2015.10. |
| 89. |
Synthesis of indium-containing nanoparticles using plasmas in water to study their effects on living body
Nanoparticles can be employed for biomedical applications such as biomarkers, drug delivery systems, and cancer therapies. They are, however, pointed out their adverse effects on human body. Here, we synthesed indium-containing nanoparticles using discharge plasmas with indium electrodes immersed in DI water and administrated nanoparticles to rats to analyze their kinetics in living body. The discharge power was 5.1 W. The electron density is 5x1017/cm3 deduced from Stark broadening of hydrogen lines. TEM observation shows the mean size of primary nanoparticles is 7 nm. The nanoparticles are indium crystalline and indium hydroxide crystalline. The synthesized nanoparticles and purchased nanoparticles (In2O3, |
| 90. |
Substrate temperature dependence of Au-induced crystalline Ge film formation using sputtering deposition
We are developing Au-induced crystalline Ge film formation using sputtering deposition. For the method, very thin Au films were deposited on SiO2 substrates and then Ge atoms were irradiated to the Au films by sputtering. We found two kinds of Ge film growth: one is Ge film formation on Au films, and the other is Ge film formed between Au films and SiO2. The latter film formation, however, takes place in a narrow temperature range around 140°C. Here we report two kinds of substrate temperature dependence of Ge film formation: one is annealing temperature of Au films, and the other is the substrate temperature dependence during Ge sputtering. 30nm-thick Au films were deposited quartz glass as a catalyst at room temperature by sputtering. Then the Au films were annealed in a temperature range from room temperature to 190 °C in a vacuum. Au grain grows and crystal orientation shows better alignment as the annealing temperature rises. We found that the smaller grain size with random orientation is better for Ge film formed between Au films and SiO2.. |
| 91. |
Simple Evaluation Method of Atmospheric Plasma Irradiation Dose using pH of Water
Atmospheric discharge plasmas are promising for agricultural productivity improvements and novel medical therapies, because plasma provides high flux of short-lifetime reactive species at low temperature, leading to low damage to living body. For the plasma-bio applications, various kinds of plasma systems are employed, thus common evaluation methods are needed to compare plasma irradiation dose quantitatively among the systems. Here we offer simple evaluation method of plasma irradiation dose using pH of water. Experiments were carried out with a scalable DBD device. 300 μl of deionized water was prepared into the quartz 96 microwell plate at 3 mm below electrode. The pH value has been measured just after 10 minutes irradiation. The pH value was evaluated as a function of plasma irradiation dose. Atmospheric air plasma irradiation decreases pH of water with increasing the dose. We also measured concentrations of chemical species such as nitrites, nitrates and H2O2. The results indicate our method is promising to evaluate plasma irradiation dose quantitatively.. |
| 92. |
Raman spectroscopy of PIN hydrogenated amorphous silicon solar cells
Light-induced degradation of hydrogenated amorphous silicon (a-Si:H) is a key issue for enhancing competitiveness in solar cell market. A-Si:H films with a lower density of Si-H2 bonds shows higher stability. Here we identified Si-H2 bonds in PIN a-Si:H solar cells fabricated by plasma CVD using Raman spectroscopy. A-Si:H solar cell has a structure of B-doped μc-SiC:H (12.5 nm)/ non-doped a-Si:H (250nm)/ P-doped μc-Si:H (40 nm) on glass substrates (Asahi-VU). By irradiating HeNe laser light from N-layer, peaks correspond to Si-H2 bonds (2100 cm-1) and Si-H bonds (2000 cm-1) have been identified in Raman scattering spectra. The intensity ratio of Si-H2 and Si-H ISiH2/ISiH is found to correlate well to light induced degradation of the cells Therefore, Raman spectroscopy is a promising method for studying origin of light-induced degradation of PIN solar cells.. |
| 93. |
Laser trapped single fine particle as a probe of plasma parameters”
Here we report evaluation of electron density and temperature using optically trapped single fine particle. Experiments were carried out with a radio frequency low pressure plasma reactor, where we set two quartz windows as top and bottom flanges to irradiate an infrared laser light of 1064 nm wavelength from the bottom side. Ar plasmas were generated between a powered ring-electrode set at the bottom of the reactor and a grounded mesh placed at the center of the reactor at 100 Pa by applying 13.56 MHz voltage. The particles injected into the plasmas were monodisperse methyl methacrylate-polymer spheres of 10 μm in diameter. A negatively charged particle, which is suspended plasma sheath boundary, was trapped at the focal point of the irradiated laser light due to the transfer of momentum from the scattering of incident photons. At the beginning of the trapping, particle of 10 μm in size was trapped above 505 μm from the bottom window. After 230 min, the size and position were 9.56 μm and 520 μm, respectively. From the results, the electron density and temperature are deduced to be 1.7×109 cm-3 and 1.9 eV.. |
| 94. |
Effects of N2 dilution on fabrication of Ge nanoparticles by rf sputtering
Multiple exciton generation (MEG) in QDs is expected to enhance significantly the energy conversion efficiency of solar cells. Although there are several reports on MEG characteristics from various QD materials such as PbS, CdSe, CdS ZnS, and Ag2S, such materials have disadvantages of their toxicity and limited resources. Here we have developed quantum-dots (QDs) solar cells using Ge nanoparticles fabricated by rf sputtering method under high pressure. We fabricated Ge nanoparticles by rf sputtering at a pressure of 1.5 Torr. Since the mean free path of Ge atoms is an order of micrometer, and Ge nanoparticles are formed in gas phase. We fabricated Ge nanoparticles using Ar and N2 to terminate surface defects by N. Ge and Ar emission intensities decrease significantly with increasing N2 partial pressure. The electron density was measured with a plasma absorption probe. The electron density decreases with increasing N2 partial pressure.. |
| 95. |
Effects of electrode structure on characteristics of multi-hollow discharges
Silane plasmas are widely employed for hydrogenated amorphous silicon (a-Si:H) film deposition. Amorphous silicon nanoparticles below 10 nm in size (clusters) are formed in silane plasmas and some of them are incorporated into a-Si:H films, leading to the light induced degradation which is the most important issue for a-Si:H solar cells. To suppress cluster incorporation, a multi-hollow discharge plasma CVD method has been developed and succeeded in depositing highly stable a-Si:H films. For further improvement of the film qualities, we have employed a thicker grounded electrode to suppress plasma expansion toward the deposition region. From optical images of the discharge plasmas, the expansion was significantly suppressed using 10 mm thick grounded electrode. For the 10 mm thick electrode, optical emission intensity ratio of Si* (288 nm) and SiH* (414 nm) ISi*/ISiH*, which shows a ratio of cluster generation ratio and radical ones, was 20% of that for 1mm thick electrode. These results suggest that the generation of clusters was also suppressed using the 10 mm thick grounded electrode.. |
| 96. |
Deposition rate and etching rate due to neutral radicals and dust particles measured using QCMs together with a dust eliminating filter
We have developed an in-situ method for measuring deposition rate of radicals and dust particles using quartz crystal microbalances (QCMs) together with a dust eliminating filter. The QCMs have three channels of quartz crystals. Channel 1 was used to measure total deposition rate due to radicals and dust particles. Channel 2 was covered with a dust eliminating filter. Channel 3 was covered with a stainless-steel plate. Moreover, all QCMs are covered with a grounded stainless steel mesh for suppressing influx of charged particles. The measurements were conducted in the Large Helical Device in the National Institute for Fusion Science, Japan. Although the deposition measurements during the discharges were difficult, we obtained deposition rate and etching rate by comparing the data before and after each discharge. The frequency difference for channel 1 changes from 0.1 Hz (etching) to -0.5 Hz (deposition), while those for channels 2 and 3 are within a range of +/-0.1 Hz and +/-0.05 Hz, respectively. The QCM method gives information on deposition rate and etching rate due to neutral radicals and dust particles.. |
| 97. |
Cross correlation analysis of plasma perturbation in amplitude modulated reactive dusty plasmas
Interactions between plasmas and nano-interface are one of the most important issues in plasma processing. We have studied effects of plasma perturbation on growth of nanoparticles in amplitude modulated reactive dusty plasmas and have clarified that amplitude modulation (AM) leads to suppression of growth of nanoparticles [1]. Here we report results of cross correlation analysis of time evolution of laser light scattering intensity from nanoparticles in reactive plasmas. Experiments were carried out using a capacitively-coupled rf discharge reactor with a two-dimensional laser light scattering (LLS) system. We employed Ar +DM-DMOS discharge plasmas to generate nanoparticles. The peaks at higher harmonics and subharmonics in spectra of laser light scattering intensity were detected, suggesting nonlinear coupling between plasma and nanoparticle amount. We found high cross correlation t between waves at AM frequency and its higher harmonics. Namely, perturbation at fAM closely correlates with those at higher harmonics.. |
| 98. |
Cluster Incorporation into A-Si:H Films Deposited Using H 2 +SiH 4 Discharge Plasmas
Light-induced degradation is the most important issue for hydrogenated amorphous silicon (a-Si:H) solar cells. Our previous results have suggested that incorporation of clusters into films is responsible for the light-induced degradation. Therefore, it is important to control the incorporation of clusters. Recently, we have developed multi-hollow discharge plasma CVD method, by which clusters are driven toward the downstream region and high quality a-Si:H films can be deposited in the upstream region. Here, we report effects of H2 dilution on cluster incorporation. Cluster size was measured by TEM, and the incorporation amount of clusters was measured with quartz crystal microbalances. H2 dilution leads to smaller clusters and the cluster incorporation in the upstream region increases with H2 dilution because the diffusion velocity of such small clusters much surpasses gas flow velocity.. |
| 99. |
Attraction during binary collision of fine particles in Ar plasma
Forces exerted on fine particles in plasmas play central roles in their transport, agglomeration, as well as Coulomb crystals and liquids. The forces are complicated because of charge fluctuation of fine particles, charge screening in plasma, anisotropy of plasma flow, and so on. Various formulas of such forces have been theoretically predicted but many of them have not been supported by experimental results yet. Here we carried out experiments on binary collision of fine particles using Ar rf-discharge plasmas. PMMA fine particles of 10 μm diameter were injected into the plasma and they were levitated around the plasma sheath boundary. The number of fine particles levitated was so small that we can observe non-collective pair interaction. We observed binary collisions of fine particles with a high speed and high resolution camera. We found that repulsion of two fine particles takes place in short distances, whereas attraction takes place in middle distances. These results indicate that inter-molecular like potential exists between them. The attraction corresponds to non-collective fine-particle attraction due to shadow effects.. |
| 100. |
Mizuki Tateishi, Kazunori Koga, Ryu Katayama, Daisuke Yamashita, Kunihiro Kamataki, Hyunwoong Seo, Naho Itagaki, Masaharu Shiratani, Naoko Ashikawa, Suguru Masuzaki, Kiyohiko Nishimura, Akio Sagara, Real-time mass measurement of dust particles deposited on vessel wall in a divertor simulator using quartz crystal microbalances, JOURNAL OF NUCLEAR MATERIALS, 10.1016/j.jnucmat.2014.10.049, 463, 865-868, 2015.08, We are developing a dust monitoring method using quartz crystal microbalances (QCMs) equipped with a dust eliminating filter. Here we report a dust eliminating ratio of the filter and first measurement results of the QCMs in a divertor simulator. The volume of spherical dust in unit area on the filter and QCM under the filter were 2.09 x 10(-9) and 1.22 x 10(-19) m(3) m(-2), respectively. Thus, the dust eliminating ratio of the filter is 94.2%. The QCM without the filter gives deposition rate due to radicals and dust particles, whereas the QCM with the filter gives deposition rate predominantly due to radicals. From the results, we deduce information of mass fraction of dust particles in deposits. (C) 2014 Elsevier B.V. All rights reserved.. |
| 101. |
Koichi Matsushima, Ryota Shimizu, Tomoaki Ide, Daisuke Yamashita, Hyunwoong Seo, Kazunori Koga, Masaharu Shiratani, Naho Itagaki, Fabrication of ZnInON/ZnO multi-quantum well solar cells, THIN SOLID FILMS, 10.1016/j.tsf.2015.01.012, 587, 106-111, 2015.07, We report on fabrication and photovoltaic characteristics of solar cells with ZnInON/ZnO multi-quantum wells (MQWs) in the intrinsic layer of p-i-n structure by RFmagnetron sputtering. We employed two kinds of p layers: one is p-GaN and the other is p-Si. Under solar simulator light, the short-circuit current (J(sc)) and the open-circuit voltage (V-oc) of the solar cells on p-GaN templates are 1.9 mu A/cm(2) and 0.16 V, whereas J(sc) and V-oc are enhanced to 2.5 mu A/cm(2) and 0.19 V under simultaneous irradiation of green laser light (532 nm) and the solar simulator light. Solar cells on p-Si substrates do not show such enhancement. A possible origin of the enhancement is a large piezoelectric field generated in strained ZnInON wells coherently grown on p-GaN template. (C) 2015 Elsevier B.V. All rights reserved.. |
| 102. |
X. Dong, K. Koga, D. Yamashita, H. Seo, N. Itagaki, M. Shiratani, Y. Setsuhara, M. Sekine, M. Hori, Effects of discharge voltage on the characteristics of a-C:H films prepared by H-assisted Plasma CVD method, Trans. Mater. Res. Soc. Jpn., 10.14723/tmrsj.40.123, 40, 2, 123-128-128, 2015.07, Hydrogen bonding configurations and hydrogen content of a-C:H films deposited by H-assisted plasma CVD were investigated by Fourier transform infrared spectroscopy. Plasma parameters related to deposition rate were derived using optical emission spectroscopy. The a-C:H films contain a large number of sp3 configurations (93%) and a few sp2 configurations (7%). Most of the hydrogen is bonded in methyl groups which shows the structure of deposited a-C:H films is polymer-like carbon. The mass density has nearly linear decreases with increasing the hydrogen atom density, indicating that control of hydrogen content is crucial to obtain a-C:H films of high mass density. A slight increase in radical generation rate and significant increases in etching rate by hydrogen atoms lead to decrease the deposition rate when the discharge voltage increases from 170 V to 180 V.. |
| 103. |
Susumu Toko, Yoshihiro Torigoe, Weiting Chen, Daisuke Yamashita, Hyunwoong Seo, Naho Itagaki, Kazunori Koga, Masaharu Shiratani, Effects of cluster incorporation into hydrogenated amorphous silicon films in initial discharge phase on film stability, THIN SOLID FILMS, 10.1016/j.tsf.2015.02.052, 587, 126-131, 2015.07, We studied the effects of incorporation of hydrogenated amorphous silicon (a-Si:H) nanoparticles (clusters) generated in the initial discharge phase on light induced degradation of a-Si:H films. The amount of clusters incorporated into the films in the initial discharge phase is 15 times larger than that in the steady state. To evaluate the effects of such initial cluster incorporation on stability of a-Si:H films, we fabricated a-Si:H Schottky cells with and without initial cluster incorporation using a multi-hollow discharge plasma chemical vapor deposition method with a shutter and compared cell stability against light exposure. The degradation ratio of the cell without initial cluster incorporation is less than 1% even after 100 hour light soaking of 2.7 suns. Our results show that suppressing initial cluster incorporation into a-Si:H films is a key to stable a-Si:H cells. Moreover, Si-H-2 bonds in films can be reduced down to 1/10 using a cluster eliminating filter. (C) 2015 Elsevier B.V. All rights reserved.. |
| 104. |
Atsushi Nakajima, Giichiro Uchida, Toshiyuki Kawasaki, Kazunori Koga, Thapanut Sarinont, Takaaki Amano, Kosuke Takenaka, Masaharu Shiratani, Yuichi Setsuhara, Effects of gas flow on oxidation reaction in liquid induced by He/O-2 plasma-jet irradiation, JOURNAL OF APPLIED PHYSICS, 10.1063/1.4927217, 118, 4, 043301, 2015.07, We present here analysis of oxidation reaction in liquid by a plasma-jet irradiation under various gas flow patterns such as laminar and turbulence flows. To estimate the total amount of oxidation reaction induced by reactive oxygen species (ROS) in liquid, we employ a KI-starch solution system, where the absorbance of the KI-starch solution near 600 nm behaves linear to the total amount of oxidation reaction in liquid. The laminar flow with higher gas velocity induces an increase in the ROS distribution area on the liquid surface, which results in a large amount of oxidation reaction in liquid. However, a much faster gas flow conversely results in a reduction in the total amount of oxidation reaction in liquid under the following two conditions: first condition is that the turbulence flow is triggered in a gas flow channel at a high Reynolds number of gas flow, which leads to a marked change of the spatial distribution of the ROS concentration in gas phase. Second condition is that the dimpled liquid surface is formed by strong gas flow, which prevents the ROS from being transported in radial direction along the liquid surface. (C) 2015 AIP Publishing LLC.. |
| 105. |
K. Matsushima, R. Shimizu, T. Ide, D. Yamashita, H. Seo, K. Koga, M. Shiratani, N. Itagaki, Fabrication of p-i-n solar cells utilizing ZnInON by RF magnetron sputtering, Mat. Res. Soc. Symp. Proc., 10.1557/opl.2015.248, 1741, aa09-10, 2015.03. |
| 106. |
N. Itagaki, K. Matsushima, D. Yamashita, H. Seo, K. Koga, M. Shiratani, ZnO-based semiconductors with tunable band gap for solar sell applications, Proc. SPIE photonics west 2015, 10.1117/12.2078114, 9364, 93640P, 2015.03. |
| 107. |
X. Dong, R. Torigoe, K. Koga, G. Uchida, M. Shiratani, N. Itagaki, Y. Setsuhara, K. Takenaka, M. Sekine, M. Hori, Deposition of Carbon Films on PMMA Using H-assisted Plasma CVD, Jpn. Phys. Soc. Conf. Proc (APPC12), 10.7566/JPSCP.1.015072, 1, 015072, 2015.03. |
| 108. |
T. Ide, K. Matsushima, R. Shimizu, D. Yamashita, H. Seo, K. Koga, M. Shiratani, N. Itagaki, Effects of morphology of buffer layers on ZnO/sapphire heteroepitaxial growth by RF magnetron sputtering, Mat. Res. Soc. Symp. Proc., 10.1557/opl.2015.87, 1741, aa09-12, 2015.02. |
| 109. |
A. Tanaka, M. Hirata, N. Matsumura, K. Koga, M. Shiratani, Y. Kiyohara, Comparative Study on the Pulmonary Toxicity of Indium Hydroxide, Indium-Tin Oxide, and Indium Oxide Following Intratracheal Instillations into the Lungs of Rats, Mat. Res. Soc. Symp. Proc., 10.1557/opl.2015.21, 1723, g02-03, 2015.02. |
| 110. |
T. Sarinont, T. Amano, K. Koga, M. Shiratani, N. Hayashi, Effects of Atmospheric Air Plasma Irradiation to Seeds of Radish Sprouts on Chlorophyll and Carotenoids Concentrations in their Leaves, Mat. Res. Soc. Symp. Proc., 10.1557/opl.2015.39, 1723, g02-04, 2015.02. |
| 111. |
T. Sarinont, T. Amano, K. Koga, M. Shiratani, N. Hayashi, Multigeneration Effects of Plasma Irradiation to Seeds of Arabidopsis Thaliana and Zinnia on Their Growth, Mat. Res. Soc. Symp. Proc., 10.1557/opl.2015.12, 1723, g03-04, 2015.01. |
| 112. |
Hyunwoong Seo, Daiki Ichida, Shinji Hashimoto, Giichiro Uchida, Naho Itagaki, Kazunori Koga, Masaharu Shiratani, Photovoltaic application of Si nanoparticles fabricated by multihollow plasma discharge CVD: Dye and Si co-sensitized solar cells, JAPANESE JOURNAL OF APPLIED PHYSICS, 10.7567/JJAP.54.01AD02, 54, 1, 01AD02, 2015.01, Dye-sensitized solar cells (DSCs) still need wider absorption range despite their stable and good performance. This work proposed the co-sensitization of Si quantum dot (QD) and N749 dye for better photo-generation. Si QD was chemically stable with regard to all DSC components and its stability enabled to co-sensitize with dye. Si QDs were fabricated by multihollow discharge plasma chemical vapor deposition and applied for the co-sensitization. Si and dye co-sensitization led to the increase of incident photon to current conversion efficiency and decrease of internal impedance as compared with a standard DSC. As a result, short-circuit current density was increased over 1 mA/cm(2) and the performance was enhanced with co-sensitization from 4.36 to 5.10%. Si and dye co-sensitization was very effective because the enhancement was much larger than the performance of Si QDSC without dye sensitization. (C) 2015 The Japan Society of Applied Physics. |
| 113. |
Shinya Iwashita, Edmund Schuengel, Julian Schulze, Peter Hartmann, Zoltan Donko, Giichiro Uchida, Kazunori Koga, Masaharu Shiratani, Uwe Czarnetzki, Dust Hour Glass in a Capacitive RF Discharge, IEEE TRANSACTIONS ON PLASMA SCIENCE, 10.1109/TPS.2014.2343975, 42, 10, 2672-2673, 2014.10, Cyclic transport of dust particles (dust hour glass) in a capacitively coupled radio frequency discharge with horizontal electrodes is demonstrated. Dust transport toward the upper electrode is initiated by varying the electrical asymmetry of the discharge. A shaped upper electrode guides dust particles to move toward the center of the discharge. Subsequently, the dust drops through the plasma bulk spontaneously, this way returning to the starting location.. |
| 114. |
Toshiyuki Kawasaki, Kota Kawano, Hiroshi Mizoguchi, Yuto Yano, Keisuke Yamashita, Miho Sakai, Takako Shimizu, Giichiro Uchida, Kazunori Koga, Masaharu Shiratani, Visualization of the Distribution of Oxidizing Substances in an Atmospheric Pressure Plasma Jet, IEEE TRANSACTIONS ON PLASMA SCIENCE, 10.1109/TPS.2014.2325038, 42, 10, 2482-2483, 2014.10, A chemical interaction between an atmospheric pressure plasma jet and liquid media is of great interest for biomedical applications. In this paper, the visualization method and typical results of the 2-D distribution of oxidizing substances generated by the plasma jet were reported using the gel visualization reagent. The plasma jet generator consists of a glass tube and two electrodes. As a result, the distribution of oxidizing substances was able to be visualized around the contact point between the plasma jet and the reagent in atmospheric air. The interesting distribution patterns depending on the supplied gas were visually obtained by the reagent. In addition, its relative concentration distribution was also obtained by an absorbance measurement.. |
| 115. |
N. Itagaki, K. Matsushima, D. Yamashita, H. Seo, K. Koga, M. Shiratani, Synthesis and characterization of ZnInON semiconductor: a ZnO-based compound with tunable band gap, MATERIALS RESEARCH EXPRESS, 10.1088/2053-1591/1/3/036405, 1, 3, 036405, 2014.09, We have synthesized ZnInON (ZION) semiconductor, a ZnO-based compound with tunable band gap, by radio-frequency magnetron sputtering on quartz glass, a-SiO2/Si, and GaN/Al2O3 templates. From XRD analysis using wide-range reciprocal-space mapping, ZION is deduced to be a pseudo-binary system of wurtzite ZnO and wurtzite InN, the c-axis lattice parameter of which varies continuously from 0.53 to 0.58 nm with decreasing the chemical composition ratio [Zn]/([Zn] + [In]). From optical measurements, we found that ZION has tunability of the band gap over the entire visible spectrum, and the photo-to-dark conductivity ratio is high, of 2.2 x 10(3), demonstrating the high photosensitivity of ZION films. We have also succeeded in the epitaxial growth of ZION films with the composition ratio (InN)/(ZnO) of about 50 at.% by using GaN templates, where the FWHM of the ZION (002) rocking curve is small, of 350 arcsec. These results allow us to conclude that ZION will open up the field of group II-III-V-VI semiconductors that offer new opportunities for design of optoelectronic devices.. |
| 116. |
Naho Itagaki, Kazunari Kuwahara, Koichi Matsushima, Daisuke Yamashita, Hyunwoong Seo, Kazunori Koga, Masaharu Shiratani, Off-axis sputter deposition of ZnO films on c-sapphire substrates by utilizing nitrogen-mediated crystallization method, OPTICAL ENGINEERING, 10.1117/1.OE.53.8.087109, 53, 8, 87109, 2014.08, High-quality epitaxial ZnO films on c-plane sapphire substrates have been obtained by utilizing an off-axis sputtering configuration together with buffer layers prepared via nitrogen-mediated crystallization (NMC). The role of NMC buffer layers is to provide high density of nucleation site and, thus, to reduce the strain energy caused by the large lattice mismatch (18%) between ZnO and sapphire. The NMC buffer layers allow two-dimensional growth of subsequently grown ZnO films, being particularly enhanced by employing an off-axis sputtering configuration in which the substrate is positioned out of the high-energy particles, such as negative oxygen ions originating from the targets. As a result, ZnO films with smooth surfaces (root-mean-square roughness: 0.76 nm) and a high electron mobility of 88 cm(2)/V . s are fabricated. Photoluminescence spectra of the ZnO films show strong near-band-edge emission, and the intensity of the orange-red defect emission significantly decreases with increasing horizontal distance between the target and the substrate. From these results, we conclude that off-axis sputtering together with NMC buffer layers is a promising method for obtaining high-quality epitaxial ZnO films. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.. |
| 117. |
M. Shiratani, K. Kamataki, G. Uchida, K. Koga, H. Seo, N. Itagaki, T. Ishihara, SiC Nanoparticle Composite Anode for Li-Ion Batteries, Mat. Res. Soc. Symp. Proc., 10.1557/opl.2014.742, 1678, n08-58, 2014.07. |
| 118. |
Satoshi Kitazaki, Thapanut Sarinont, Kazunori Koga, Nobuya Hayashi, Masaharu Shiratani, Plasma induced long-term growth enhancement of Raphanus sativus L. using combinatorial atmospheric air dielectric barrier discharge plasmas, CURRENT APPLIED PHYSICS, 10.1016/j.cap.2013.11.056, 14, S149-S153, 2014.07, Combinatorial analysis has been carried out to investigate the long-term effects of plasma irradiation of radish seeds on the subsequent sprout growth (Raphanus sativus L.) using atmospheric dielectric barrier discharge plasmas in air. The average seedling length was maximized with 180 s of plasma irradiation when the seed was 5 mm from the electrode edge and 3 mm below the electrode. With these parameters the average seedling length was 250% longer than that not irradiated after three days of cultivation. Observation of the seeds using an infrared (IR) camera and scanning electron microscopy revealed that the temperature rise and etching of the seeds during the plasma irradiation have little effect on growth enhancement. The interaction between radicals and seeds for a duration of 180 s leads to the growth enhancement of radish sprouts for 7 days. (C) 2014 Elsevier B.V. All rights reserved.. |
| 119. |
T. Ito, K. Koga, D. Yamashita, K. Kamataki, N. Itagaki, G. Uchida and M. Shiratani, Plasma etching of single fine particle trapped in Ar plasma by optical tweezers, J. Phys. : Conf. Series (SPSM26), 10.1088/1742-6596/518/1/012014, 518, 1, 012014, 2014.06. |
| 120. |
X. Dong, K. Koga, D. Yamashita, H. Seo, N. Itagaki, M. Shiratani, Y. Setsuhara, M. Sekine and M. Hori, Emission spectroscopy of Ar + H-2+ C7H8 plasmas: C7H8 flow rate dependence and pressure dependence, J. Phys. : Conf. Series (SPSM26), 10.1088/1742-6596/518/1/012010, 518, 1, 012010, 2014.06. |
| 121. |
Y. Hashimoto, S. Toko, D. Yamashita, H. Seo, K. Kamataki, N. Itagaki, K. Koga and M. Shiratani, Effects of filter gap of cluster-eliminating filter on cluster eliminating efficiency, J. Phys. : Conf. Series (SPSM26), 10.1088/1742-6596/518/1/012007, 518, 1, 012007, 2014.06. |
| 122. |
D. Ichida, G. Uchida, H. Seo, K. Kamataki, N. Itagaki, K. Koga and M. Shiratani, Deposition of crystalline Ge nanoparticle films by high-pressure RF magnetron sputtering method, J. Phys. : Conf. Series (SPSM26), 10.1088/1742-6596/518/1/012002, 518, 1, 012002, 2014.06. |
| 123. |
S. Toko, Y. Hashimoto, Y. Kanemitu, Y. Torigoe, H. Seo, G. Uchida, K. Kamataki, N. Itagaki, K. Koga and M. Shiratani, Contribution of ionic precursors to deposition rate of a-Si:H films fabricated by plasma CVD, J. Phys. : Conf. Series (SPSM26), 10.1088/1742-6596/518/1/012008, 518, 1, 012008, 2014.06. |
| 124. |
M. Tateishi, K. Koga, D. Yamashita, K. Kamataki, H. Seo, N. Itagaki, M. Shiratani, N. Ashikawa, S. Masuzaki, K. Nishimura and A. Sagara, the LHD Experimental Group, Contribution of H2 plasma etching to radial profile of amount of dust particles in a divertor simulator, J. Phys. : Conf. Series (SPSM26), 10.1088/1742-6596/518/1/012009, 518, 1, 012009, 2014.06. |
| 125. |
T. Sarinont, T. Amano, S. Kitazaki, K. Koga, G. Uchida, M. Shiratani and N. Hayashi, Growth enhancement effects of radish sprouts: atmospheric pressure plasma irradiation vs. heat shock, J. Phys. : Conf. Series (SPSM26), 10.1088/1742-6596/518/1/012017, 518, 1, 012017, 2014.06. |
| 126. |
K. Koga, X. Dong, S. Iwashita, U. Czarnetzki and M. Shiratani, Formation of carbon nanoparticle using Ar+CH4 high pressure nanosecond discharges, J. Phys. : Conf. Series (SPSM26), 10.1088/1742-6596/518/1/012020, 518, 1, 012020, 2014.06. |
| 127. |
T. Kawasaki, K. Kawano, H. Mizoguchi, Y. Yano, K. Yamashita, M. Sakai, G. Uchida, K. Koga, M. Shiratani, Control of the area irradiated by the sheet-type plasma jet in atmospheric pressure, J. Phys. : Conf. Series (SPSM26), 10.1088/1742-6596/518/1/012016, 518, 1, 012016, 2014.06. |
| 128. |
Hyunwoong Seo, Daiki Ichida, Giichiro Uchida, Naho Itagaki, Kazunori Koga, Masaharu Shiratani, Performance dependence of Si quantum dot-sensitized solar cells on counter electrode, JAPANESE JOURNAL OF APPLIED PHYSICS, 10.7567/JJAP.53.05FZ01, 53, 5, 05FZ01, 2014.05, Au counter electrode is generally used with polysulfide electrolyte for quantum dot-sensitized solar cells (QDSCs) due to degradation of QD by iodine electrolyte and strong interaction between Pt counter electrode and S2- ions in polysulfide electrolyte. In this work, the effects of the thickness and morphology of Au counter electrode on the performance of Si QDSC were investigated. Au film thickness was linearly controlled from 5 to 500 nm by deposition time. Cyclic voltammetry and impedance analysis clarified the catalytic activity of counter electrode, surface resistance of transparent conductive oxide (TCO), and the charge transportation at the counter electrode. The increase of Au film thickness reduced the surface resistance of TCO with increased conductivity. No significant difference in the redox reaction from electrolyte to Si QDs was observed for Au film thickness from 20 to 500 nm. Catalytic reaction of counter electrode was activated with the increase of Au film thickness up to 200 nm. The impedance of charge transportation at the counter electrode was also decreased with Au deposition. Their surface resistance, catalytic activity and internal resistance were reflected in overall performance. Consequently, Si QDSC with 200-nm-thick Au counter electrode had the best performance. (C) 2014 The Japan Society of Applied Physics. |
| 129. |
N. Itagaki, K. Matsushima, D. Yamashita, H. Seo, K. Koga, M. Shiratani, Off-axis sputter deposition of ZnO films on c-sapphire substrates with buffer layers prepared via nitrogen-mediated crystallization, Proc. SPIE photonics west 2014, 10.1117/12.2041081 , 8987, 89871A, 2014.03. |
| 130. |
Hyunwoong Seo, Min-Kyu Son, Songyi Park, Myeongsoo Jeong, Hee-Je Kim, Giichiro Uchida, Naho Itagaki, Kazunori Koga, Masaharu Shiratani, Electrochemical impedance analysis on the additional layers for the enhancement on the performance of dye-sensitized solar cell, THIN SOLID FILMS, 10.1016/j.tsf.2013.08.103, 554, 122-126, 2014.03, A dye-sensitized solar cell is one of the representative photochemical solar cells. It has been actively studied and its performance has been much enhanced so far. For better performance, various additional layers such as compact, barrier, and light scattering layers have been applied. Compact and barrier layers suppress the charge recombination with redox electrolyte and light scattering layer improves the light harvesting. Although it was confirmed that these layers were clearly effective for the performance enhancement, there is still a variety of opinions concerning their electrochemical impedance analyses. Therefore, this work tried to analyze their effect on the internal impedance using electrochemical impedance spectroscopy. The most widely used materials were employed for the fabrication of additional layers. TiCl4 and Zn(NO3)(2)-6H(2)O aqueous solutions, and a 400 nmsized TiO2 were used for compact, barrier, and light scattering layers, respectively. The photovoltaic characteristics confirmed their effect on the performance and their impedance spectrawere analyzed according to high, middle, and low frequency bands. As a result, these layers mainly affected the impedance in the middle frequency range because the change of TiO2/dye/electrolyte interface was significantly associated with this impedance. Finally, all three layers were applied to a single cell and the performance was considerably increased with reduced charge recombination and improved light harvesting. (C) 2013 Elsevier B. V. All rights reserved.. |
| 131. |
T. Sarinont, K. Koga, S. Kitazaki, G. Uchida, N. Hayashi, M. Shiratani, Effects of Atmospheric Air Plasma Irradiation on pH of Water, JPS Conf. Proc., 10.7566/JPSCP.1.015078, 1, 015078, 2014.03. |
| 132. |
X. Dong, K. Koga, D. Yamashita, H. Seo, N. Itagaki, M. Shiratani, K. Takenaka, Y. Setsuhara, M. Sekine, M. Hori, Pressure dependence of carbon film deposition using H-assisted plasma CVD, Proc. 8th Int. Conf. Reactive Plasmas, 5P-PM-S08-P14, 2014.02. |
| 133. |
Hyunwoong Seo, Daiki Ichida, Giichiro Uchida, Kunihiro Kamataki, Naho Itagaki, Kazunori Koga, Masaharu Shiratani, Analysis on the Photovoltaic Property of Si Quantum Dot-Sensitized Solar Cells, INTERNATIONAL JOURNAL OF PRECISION ENGINEERING AND MANUFACTURING, 10.1007/s12541-014-0343-8, 15, 2, 339-343, 2014.02, This work first introduced Si quantum dots (QDs) for QD-sensitized solar cells (QDSCs). However, the particle size of Si QDs, which had visible light absorption, was relatively large. The paint-type Si QDSC was proposed in this work because Si QDs could not penetrate into nano-porous TiO2 network. Si QDs were synthesized by multi-hollow plasma discharge CVD and mixed with TiO2 paste. For better performance, thickness of Si-TiO2 layer was varied by coating times and Si-TiO2 films were optically and electrically analyzed. As a result, 6 times screen printed Si-TiO2 film had the best performance with the smallest internal impedance and the highest photon to current efficiency.. |
| 134. |
T. Kawasaki, K. Kawano, H. Mizoguchi, Y. Yano, K. Yamashita, M. Sakai, G. Uchida, K. Koga, M. Shiratani, Visualization of oxidizing substances generated by atmospheric pressure non-thermal plasma jet with water, Proc. 8th Int. Conf. Reactive Plasmas, 4P-PM-S09-P25, 2014.02. |
| 135. |
K. Koga, T. Sarinont, S. Kitazaki, N. Hayashi, M. Shiratani, Multi-generation evaluation of plasma growth enhancement to arabidopsis thaliana (Invited), Proc. 8th Int. Conf. Reactive Plasmas, 6C-PM-A4, 2014.02. |
| 136. |
T. Amano, T. Sarinont, S. Kitazaki, N. Hayashi, K. Koga, M. Shiratani, Long term growth of radish sprouts after atmospheric pressure DBD plasma irradiation to seeds, Proc. 8th Int. Conf. Reactive Plasmas, 5P-PM-S12-P33, 2014.02. |
| 137. |
T. Sarinont, K. Koga, S. Kitazaki, M. Shiratani, N. Hayashi, Effects of growth enhancement by plasma irradiation to seeds in water, Proc. 8th Int. Conf. Reactive Plasmas, 5P-PM-S12-P32, 2014.02. |
| 138. |
Performance enhancement of dye and Si quantum dot hybrid nanostructured solar cell with TiO2 barrier
Dye and quantum dot (QD) are representative sensitizers of the photochemical solar cells. Dye has the highest efficiency in the whole sensitizers. QDs have relatively low performance but their multiple exciton generation enhanced theoretical efficiency from 33 to 44% and expected to achieve high efficiency. This work tried to enhance the photovoltaic performance with the co-sensitization of N719 dye and Si QD. The performance of dye and QD co-sensitized solar cell was not much enhanced because of electron loss of charge recombination. Therefore, TiO2 barrier layer was introduced on TiO2 and Si QD. It blocked the charge recombination with redox electrolyte. It also helped better electron injection from excited dye to TiO2 with strengthened dye adsorption. Consequently, the performance of co-sensitized solar cell was enhanced with reduced charge recombination and increased dye adsorption.. |
| 139. |
Sputter deposition of high quality ZnO films
We have developed a novel fabrication method based on sputtering, “Impurity Mediated Crystallization (IMC)”, for crystal growth control of ZnO. The crystal grain density as well as the surface morphology of ZnO films have been controlled by the adsorption/desorption behavior of nitrogen atoms at the film surface. As a result, two kinds of ZnO films have been fabricated, the properties of which are far superior to those of conventional ZnO films. One is ZnO:Al transparent conducting oxide with a low resistivity of 3×10-4Ω?cm in the thickness range of 20-200 nm, and the other is single crystalline ZnO with an atomically flat surface.. |
| 140. |
Nanostructure control of Si and Ge quantum dots based solar cells using plasma processes
We report characteristics of quantum dot (QD) sensitized solar cells using Si nanoparticles and Ge nanoparticles. Si nanoparticles were synthesized by multi-hollow discharge plasma chemical vapor deposition, whereas Ge nanoparticles were done by a radio frequency magnetron sputtering using Ar+H2 under high pressure conditions. The electrical power generation from Si QDs and Ge QDs was confirmed. Si QD sensitized solar cells show an efficiency of 0.024%, fill factor of 0.32, short-circuit current of 0.75 mA/cm2 and open-circuit voltage of 0.10 V, while Ge QD sensitized solar cells show an efficiency of 0.036%, fill factor of 0.38, short-circuit current of 0.64 mA/cm2 and open-circuit voltage of 0.15 V. © (2014) Trans Tech Publications, Switzerland.. |
| 141. |
Study on the Crystal Growth Mechanism of ZnO Films Fabricated Via Nitrogen Mediated Crystallization
Effects of nitrogen addition to the sputtering atmosphere on crystal growth of ZnO films have been studied. The AFM characterization shows that the nitrogen suppresses the nucleation in the early stage of the crystal growth leading to a non-continue film structure with sparsely distributed grains. As the deposition time increases, the physical properties of the ZnO films are modified by enhancement of adatoms migration at the growing surface, thus homogenous and dense films with larger grain size are obtained. Utilizing these ZnO films as buffer layers with film thickness greater than 4?nm, the electrical resistivity of ZnO:Al films have been significantly decreased from 7.8 × 10?3?Ω?cm to 6.7 × 10?4?Ω?cm.. |
| 142. |
Spatial Profile of Flux of Dust Particles Generated due to Interaction between Hydrogen Plasmas and Graphite Target
We have measured spatial profile of flux of dust particles generated due to interaction between H2 plasmas and graphite target in a divertor simulator to study transport mechanism of dust particles. Dust particles were collected on c-Si substrates and observed with a scanning electron microscope. We have found nanostructure of 10?nm in size on the substrate surface. Dust fluxes of both spherical dust particles and flakes are maximum at a position between 80 and 140?mm from the center of the plasma column. The spatial profile of dust flux is determined by the balance between deposition of nanoparticles and their etching by H atoms.. |
| 143. |
Effects of H2 Gas Addition on Structure of Ge Nanoparticle Films Deposited by High-pressure RF Magnetron Sputtering Method
We have deposited crystalline Ge nanoparticle films using a radio frequency magnetron sputtering method in argon and hydrogen gas mixture under a high pressure condition. Raman spectra and X-ray diffraction pattern of Ge nanoparticle films show a transition from amorphous to crystalline by adding H2 gas.. |
| 144. |
Effects of Grid DC Bias on Incorporation of Si Clusters into Amorphous Silicon Thin Films in Multi-Hollow Discharge Plasma CVD
Si clusters formed in silane discharge plasmas are mainly responsible for light induced degradation of hydrogenated amorphous Si (a-Si:H) thin films deposited by the plasmas. Here we have investigated effects of grid DC bias on incorporation amount of Si clusters into a-Si:H films in multi-hollow discharge plasma CVD reactor using quartz crystal microbalances, by which volume fraction of Si clusters in deposited films is quantitatively measured. When the grid potential is lower than plasma potential, the negatively charged clusters are repelled away from the grid by electrostatic force, resulting in lower volume fraction.. |
| 145. |
Correlation between nanoparticle growth and plasma parameters in low pressure reactive VHF discharge plasmas
We report experimental results on correlation between plasma parameters and growth of nanoparticles in capacitively-coupled VHF discharges with amplitude modulation (AM) obtained using two dimensional laser light scattering (LLS) method. Power spectra of floating potential, Ar 810.27?nm emission intensity, and LLS intensity have peaks at the modulation frequency of 100?Hz and its second harmonics, indicating linear correlation between plasma parameters and growth of nanoparticles, that is, their size and/or density. The power spectrum of LLS intensity has another peak at 60?Hz, which coincides with our theoretical prediction of plasma fluctuation induceed nonlinear response of nanoparticle growth.. |
| 146. |
Combinatorial Plasma CVD of Si Nanoparticle Composite Films for Band Gap Control
Crystalline Si nanoparticles were successfully fabricated by a multi-hollow discharge plasma CVD method. Optical band gap of Si-nanoparticle composite films was controlled in a range of 1.6?1.9?eV by the volume fraction of Si nanoparticles in the films. SiN nanoparticle composite films were also successfully produced using a double multi-hollow discharge plasma CVD method in SiH4/H2 and N2 gas mixture. High optical band gap of 2.1?2.2?eV was achieved by adding N atoms to the Si naoparticles.. |
| 147. |
Substrate temperature dependence of hydrogen content of a-Si:H film deposited with a cluster-eliminating filter. |
| 148. |
Subacute toxicity of gallium arsenide, indium arsenide and arsenic trioxide following intermittent intrantracheal instillations to the lung of rats. |
| 149. |
Study on nitrogen desorption behavior of sputtered ZnO for transparent conducting oxide. |
| 150. |
Sputtering fabrication of a novel widegap semiconductor ZnGaON for optoelectronic devices with wide bandgap for optical device. |
| 151. |
Sputter Deposition of Ga-doped Zinc Oxide (GZO) Films with Buffer Layers Fabricated via Nitrogen Mediated Crystallization. |
| 152. |
Spatial profile of flux of dust particles in hydrogen helicon plasmas”, Proc. 8th Int. Conf. Reactive Plasmas. |
| 153. |
Raman spectroscopy of a fine particle optically trapped in plasma”, Proc. 8th Int. Conf. Reactive Plasmas. |
| 154. |
Nanoparticle amount in reactive plasmas with amplitude modulation detected by twodimensional laser light scattering method. |
| 155. |
Magnetron sputtering of low-resistive In2O3:Sn films with buffer layers fabricated via nitrogen mediated crystallization. |
| 156. |
Fine response of deposition rate of Si films deposited by multi-hollow discharge plasma CVD with amplitude modulation. |
| 157. |
Fabrication of size-controlled Ge nanoparticle films varying gas flow rate using high pressure rf magnetron sputtering method. |
| 158. |
Fabrication of SiC nanoparticles as high capacity electrodes for Li-ion batteries. |
| 159. |
Fabrication of In-rich ZnInON filmswith narrow band gap by RF magnetron sputtering. |
| 160. |
Epitaxial growth of ZnO films on sapphire substrates by magnetron sputtering: Effects of buffer layers prepared via nitrogen mediated crystallization. |
| 161. |
Effects of amplitude modulation on deposition of hydrogenated amorphous silicon films using multi-Hollow discharge plasma CVD method. |
| 162. |
Deposition of Crystalline Ge Nanoparticle Films Varying H2 Dilution Ratio Using High Pressure rf Magnetron Sputtering. |
| 163. |
Coupling between radicals and nanoparticles in initial growth phase in reactive plasmas with amplitude modulation. |
| 164. |
Combinatorial evaluation of optical properties of crystalline Si nanoparticle embedded Si films deposited by a multi-hollow discharge plasma CVD method. |
| 165. |
Analysis of fluctuation of Ar metastable density and nanoparticle amount in capacitively coupled discharges with amplitude modulation. |
| 166. |
A model for correlation between plasma fluctuation and fluctuation of nanoparticle growth in reactive plasmas. |
| 167. |
Masaharu Shiratani, Kazunori Koga, Kunihiro Kamataki, Shinya Iwashita, Giichiro Uchida, Hyunwoong Seo, Naho Itagaki, Theory for correlation between plasma fluctuation and fluctuation of nanoparticle growth in reactive plasmas, JAPANESE JOURNAL OF APPLIED PHYSICS, 10.7567/JJAP.53.010201, 53, 1, 010201, 2014.01, We propose a simple theoretical model that describes the correlation between plasma fluctuation and fluctuation of nanoparticle growth in reactive plasmas. The model predicts that the high density of nanoparticles brings about small mean-size, narrow size dispersion, and sharp size slope on the large side of the size distribution. The model suggests some methods of tuning the size dispersion, and it also suggests that a self-limiting process is the key to markedly suppressing fluctuations in nanostructure fabrication. All predictions coincide with the experimental results reported previously. Moreover, the model suggests that plasma fluctuation induces both the linear and nonlinear responses of nanoparticle growth. (C) 2014 The Japan Society of Applied Physics. |
| 168. |
Hyunwoong Seo, Yuting Wang, Muneharu Sato, Giichiro Uchida, Kazunori Koga, Naho Itagaki, Kunihiro Kamataki, Masaharu Shiratani, The improvement on the performance of quantum dot-sensitized solar cells with functionalized Si, THIN SOLID FILMS, 10.1016/j.tsf.2013.04.073, 546, 284-288, 2013.11, Quantum dots (QDs) have been attractive recently with their multiple exciton generation characteristics. QD solar cells can more effectively use the incident energy because one or more electrons are generated with the photon of high energy. They have less heat loss and higher theoretical efficiency (44%) than single exciton generation solar cells (33%). This work focused on Si as alternative to conventional QD materials. Si has QD's unique characteristics such as the quantum size effect and quantum confinement with non-toxicity and abundance. Si QDs were fabricated by the multi-hollow discharge plasma chemical vapor deposition and applied to QD-sensitized solar cells (QDSCs). Contrary to the good characteristics of Si QDs, Si QDSCs had poor performance as compared with conventional QDSCs because of the weak combination between Si QDs and TiO2. Small amounts of adsorbed Si QD on TiO2 made low photocurrent and TiO2 surface widely exposed to redox electrolyte caused charge recombination, the decrease of open-circuit voltage, and low fill factor. For improving their combination, Si QDs were functionalized. The electron transfer from Si to TiO2 and the bonding with TiO2 were improved and more Si QDs were adsorbed by the functionalization. In the functionalization process, the linking source is one of the key parameters. Therefore, 4-vinylbenzoic acid was controlled and its effect was analyzed. The change in the photovoltaic parameters according to the concentration of 4-vinylbenzoic acid and the performance dependence were investigated. In order to verify their characteristics, the effects in terms of the photovoltaic performance, electrochemical impedance, and optical properties were examined. (C) 2013 Elsevier B.V. All rights reserved.. |
| 169. |
Hyunwoong Seo, Yuting Wang, Daiki Ichida, Giichiro Uchida, Naho Itagaki, Kazunori Koga, Masaharu Shiratani, Sang-Hun Nam, Jin-Hyo Boo, Improvement on the electron transfer of dye-sensitized solar cell using vanadium doped TiO2, Japanese Journal of Applied Physics, 10.7567/JJAP.52.11NM02, 52, 11, 11NM02, 2013.11, In dye-sensitized solar cells, nanoporous structure of TiO2 is very important for efficient cell because lots of dye molecules are adsorbable and they are the source of the photocurrent. However, the internal impedance of TiO2 is relatively large and it limits the performance. For better performance, vanadium was doped into TiO2 in this work. Doping different material generally improves the characteristics and functions of original materials. Vanadium doping has some advantages such as the reduction of internal resistance, the improvement of chemical stability and high absorption. Especially, reduced internal resistance is so helpful for better electron transfer in TiO2 network. Various amounts of vanadium were applied and photovoltaic performance, internal impedance and absorbance were measured in order to verify the effect of vanadium doping. As a result, vanadium doping improved the overall performance from 6.01 to 6.81% with decreased internal resistance although adsorbed dye amount was reduced by decreased surface area and open circuit voltage was also decreased by the change of band-gap energy. © 2013 The Japan Society of Applied Physics.. |
| 170. |
Kazunori Koga, Mizuki Tateishi, Katsushi Nishiyama, Giichiro Uchida, Kunihiro Kamataki, Daisuke Yamashita, Hyunwoong Seo, Naho Itagaki, Masaharu Shiratani, Naoko Ashikawa, Suguru Masuzaki, Kiyohiko Nishimura, Akio Sagara, Flux Control of Carbon Nanoparticles Generated due to Interactions between Hydrogen Plasmas and Graphite Using DC-Biased Substrates, JAPANESE JOURNAL OF APPLIED PHYSICS, 10.7567/JJAP.52.11NA08, 52, 11, 11NA08, 2013.11, Flux control of dust particles in a nanometer size range using dc bias voltage is discussed based on dust collection in a divertor simulator employed helicon hydrogen discharges. To discuss mechanisms of flux control, we have estimated etching rate of deposited dust particles due to hydrogen plasma irradiation and have measured current density toward the dc biased substrates. We have found the contribution of the etching can be negligible in a dc bias voltage V-bias range between similar to 50 and 70 V. Clear correlation between V-bias dependence of current density and that of dust flux shows electrostatic force is one of important forces for controlling flux of dust particles. (C) 2013 The Japan Society of Applied Physics. |
| 171. |
Koichi Matsushima, Tadafumi Hirose, Kazunari Kuwahara, Daisuke Yamashita, Giichiro Uchida, Hyunwoong Seo, Kunihiro Kamataki, Kazunori Koga, Masaharu Shiratani, Naho Itagaki, Epitaxial Growth of ZnInON Films with Tunable Band Gap from 1.7 to 3.3 eV on ZnO Templates, JAPANESE JOURNAL OF APPLIED PHYSICS, 10.7567/JJAP.52.11NM06, 52, 11, 11NM06, 2013.11, Epitaxial ZnInON (ZION) films with a tunable band gap have been successfully fabricated by RF magnetron sputtering on ZnO templates prepared via nitrogen mediated crystallization (NMC). X-ray diffraction (XRD) measurements show that the full widths at half maximum of the rocking curves from (002) and (101) planes are small at 0.10 and 0.08 degrees, respectively, indicating a high crystallinity with good in-plane and out-of-plane alignments. Since the coherent growth of 35-nm-thick ZION films on NMC-ZnO templates is deduced from the reciprocal space mapping around the (105) diffraction, there is little lattice relaxation at the interface between the films and templates, which is significant in terms of the suppression of carrier recombination. The band gap of the ZION films has been tuned in a wide range of 1.7-3.3 eV by changing the Zn:In ratio. These results indicate that ZION is a potential absorption layer material of solar cells. (C) 2013 The Japan Society of Applied Physics. |
| 172. |
Iping Suhariadi, Kouichiro Oshikawa, Kazunari Kuwahara, Kouichi Matsushima, Daisuke Yamashita, Giichiro Uchida, Kazunori Koga, Masaharu Shiratani, Naho Itagaki, Effects of Nitrogen on Crystal Growth of Sputter-Deposited ZnO Films for Transparent Conducting Oxide, JAPANESE JOURNAL OF APPLIED PHYSICS, 10.7567/JJAP.52.11NB03, 52, 11, 11NB03, 2013.11, We have studied the effects of the N-2 gas flow rate on the surface morphology of ZnO films deposited by the sputtering of a ZnO target using Ar/N-2. Height-height correlation function (HHCF) analysis indicates that introducing a small amount of N-2 ( |
| 173. |
Yeonwon Kim, Kosuke Hatozaki, Yuji Hashimoto, Giichiro Uchida, Kunihiro Kamataki, Naho Itagaki, Hyunwoong Seo, Kazunori Koga, Masaharu Shiratani, Correlation between Volume Fraction of Silicon Clusters in Amorphous Silicon Films and Optical Emission Properties of Si* and SiH*, JAPANESE JOURNAL OF APPLIED PHYSICS, 10.7567/JJAP.52.11NA07, 52, 11, 11NA07, 2013.11, The volume fraction of silicon clusters in amorphous silicon (a-Si: H) films has been investigated using specially designed quartz crystal microbalances (QCMs) together with optical emission spectroscopy (OES). The optical emission intensities of Si* and SiH* and their intensity ratios are selected for comparison with the QCM results. We show that the volume fraction of silicon clusters strongly correlates with not only the electron temperature but also the SiH* intensity. This suggests that the ratios of Si*/SiH* and SiH* can be used to predict the volume fraction of Si clusters in a-Si: H films. (C) 2013 The Japan Society of Applied Physics. |
| 174. |
Giichiro Uchida, Yuting Wang, Daiki Ichida, Hyunwoong Seo, Kunihiro Kamataki, Naho Itagaki, Kazunori Koga, Masaharu Shiratani, Characteristics of Crystalline Silicon/Si Quantum Dot/Poly(3,4-ethylenedioxythiophene) Hybrid Solar Cells, JAPANESE JOURNAL OF APPLIED PHYSICS, 10.7567/JJAP.52.11NA05, 52, 11, 11NA05, 2013.11, Here, we report the characteristics of a novel organic/inorganic hybrid photovoltaic device using a Si quantum dot (QD) layer synthesized by multi-hollow discharge plasma chemical vapor deposition. The hybrid device has a p-i-n structure, which consists of a crystalline Si (c-Si) substrate, a Si QD layer, and poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS). We have examined the absorption coefficient and photoconductivity of Si QD layers, and confirmed electricity generation from Si QD layers. We have measured the current-voltage characteristics and incident photon-to-current conversion efficiency (IPCE) of c-Si/Si QD/poly(3,4-ethylenedioxythiophene) (PEDOT) hybrid solar cells. This hybrid device shows an energy conversion efficiency of 2.84%, a short-circuit current of 6.84 mA/cm(2), an open-circuit voltage of 0.73 V, and a fill factor of 0.58. A high IPCE value of 82.8% is obtained at a short wavelength of 460 nm. (C) 2013 The Japan Society of Applied Physics. |
| 175. |
Hyunwoong Seo, Min-Kyu Son, Hee-Je Kim, Yuting Wang, Giichiro Uchida, Kunihiro Kamataki, Naho Itagaki, Kazunori Koga, Masaharu Shiratani, Study on the Fabrication of Paint-Type Si Quantum Dot-Sensitized Solar Cells, JAPANESE JOURNAL OF APPLIED PHYSICS, 10.7567/JJAP.52.10MB07, 52, 10, 10MB07, 2013.10, Quantum dots (QDs) have attracted much attention with their quantum characteristics in the research field of photochemical solar cells. Si QD was introduced as one of alternatives to conventional QD materials. However, their large particles could not penetrate inside TiO2 layer. Therefore, this work proposed the paint-type Si QD-sensitized solar cell. Its heat durability was suitable for the fabrication of paint-type solar cell. Si QDs were fabricated by multihollow discharge plasma chemical vapor deposition and characterized. The paste type, sintering temperature, and Si ratio were controlled and analyzed for better performance. Finally, its performance was enhanced by ZnS surface modification and the whole process was much simplified without sensitizing process. (C) 2013 The Japan Society of Applied Physics. |
| 176. |
Giichiro Uchida, Muneharu Sato, Hyunwoong Seo, Kunihiro Kamataki, Naho Itagaki, Kazunori Koga, Masaharu Shiratani, Characteristics of photocurrent generation in the near-ultraviolet region in Si quantum-dot sensitized solar cells, THIN SOLID FILMS, 10.1016/j.tsf.2013.04.111, 544, 93-98, 2013.10, We have studied photocurrent generation in Si quantum-dot (QD) sensitized solar cells, where QD thin films composed of Si nanoparticles were deposited using the double multi-hollow discharge plasma chemical vapor deposition process in an SiH4/H-2 and CH4 or N-2 gas mixture. The short-circuit current density of the Si QD sensitized solar cells increases by a factor of 2.5 by using Si nanoparticles prepared by irradiation of CH4 or N-2 plasma onto the Si nanoparticle surface. We have measured incident photon-to-current conversion efficiency (IPCE) in the near-ultraviolet range using quartz-glass front panels of the QD sensitized solar cells. With decreasing the wavelength of irradiation light, IPCE gradually increases upon light irradiation in a wavelength range less than about 600 nm, and then steeply increases below 300 nm, corresponding to 2.2 times the optical band-gap energy of Si QD film. (C) 2013 Elsevier B.V. All rights reserved.. |
| 177. |
O. Kaneko, H. Yamada, S. Inagaki, M. Jakubowski, S. Kajita, S. Kitajima, Kobayashi, K. Koga, T. Morisaki, S. Morita, T. Mutoh, S. Sakakibara, Y. Suzuki, H. Takahashi, K. Tanaka, K. Toi, Y. Yoshimura, T. Akiyama, Y. Asahi, N. Ashikawa, H. Chikaraishi, A. Cooper, D. S. Darrow, E. Drapiko, P. Drewelow, X. Du, A. Ejiri, M. Emoto, T. Evans, N. Ezumi, K. Fujii, T. Fukuda, H. Funaba, M. Furukawa, D. A. Gates, M. Goto, T. Goto, W. Guttenfelder, S. Hamaguchi, M. Hasuo, T. Hino, Y. Hirooka, K. Ichiguchi, K. Ida, H. Idei, T. Ido, H. Igami, K. Ikeda, S. Imagawa, T. Imai, M. Isobe, M. Itagaki, T. Ito, K. Itoh, S. Itoh, A. Iwamoto, K. Kamiya, T. Kariya, H. Kasahara, N. Kasuya, D. Kato, T. Kato, K. Kawahata, F. Koike, S. Kubo, R. Kumazawa, D. Kuwahara, S. Lazerson, H. Lee, S. Masuzaki, S. Matsuoka, H. Matsuura, A. Matsuyama, C. Michael, D. Mikkelsen, O. Mitarai, T. Mito, J. Miyazawa, G. Motojima, K. Mukai, A. Murakami, I. Murakami, S. Murakami, T. Muroga, S. Muto, K. Nagaoka, K. Nagasaki, Y. Nagayama, N. Nakajima, H. Nakamura, Y. Nakamura, H. Nakanishi, H. Nakano, T. Nakano, K. Narihara, Y. Narushima, K. Nishimura, S. Nishimura, M. Nishiura, Y. M. Nunami, T. Obana, K. Ogawa, S. Ohdachi, N. Ohno, N. Ohyabu, T. Oishi, M. Okamoto, A. Okamoto, M. Osakabe, Y. Oya, T. Ozaki, N. Pablant, B. J. Peterson, A. Sagara, K. Saito, R. Sakamoto, H. Sakaue, M. Sasao, K. Sato, M. Sato, K. Sawada, R. Seki, T. Seki, V. Sergeev, S. Sharapov, I. Sharov, A. Shimizu, T. Shimozuma, M. Shiratani, M. Shoji, S. Sudo, H. Sugama, C. Suzuki, K. Takahata, Y. Takeiri, Y. Takemura, M. Takeuchi, H. Tamura, N. Tamura, H. Tanaka, T. Tanaka, M. Tingfeng, Y. Todo, M. Tokitani, K. Tokunaga, T. Tokuzawa, H. Tsuchiya, K. Tsumori, Y. Ueda, L. Vyacheslavov, K. Y. Watanabe, T. Watanabe, T. H. Watanabe, B. Wieland, I. Yamada, S. Yamada, S. Yamamoto, N. Yanagi, R. Yasuhara, M. Yokoyama, N. Yoshida, S. Yoshimura, T. Yoshinaga, M. Yoshinuma, A. Komori, Extension of operation regimes and investigation of three-dimensional currentless plasmas in the Large Helical Device, NUCLEAR FUSION, 10.1088/0029-5515/53/10/104015, 53, 10, 104015, 2013.10, The progress of physical understanding as well as parameter improvement of net-current-free helical plasma is reported for the Large Helical Device since the last Fusion Energy Conference in Daejeon in 2010. The second low-energy neutral beam line was installed, and the central ion temperature has exceeded 7 keV, which was obtained by carbon pellet injection. Transport analysis of the high-T-i plasmas shows that the ion-thermal conductivity and viscosity decreased after the pellet injection although the improvement does not last long. The effort has been focused on the optimization of plasma edge conditions to extend the operation regime towards higher ion temperature and more stable high density and high beta. For this purpose a portion of the open helical divertors are being modified to the baffle-structured closed ones aimed at active control of the edge plasma. It is compared with the open case that the neutral pressure in the closed helical divertor increased by ten times as predicted by modelling. Studies of physics in a three-dimensional geometry are highlighted in the topics related to the response to a resonant magnetic perturbation at the plasma periphery such as edge-localized-mode mitigation and divertor detachment. Novel approaches of non-local and non-diffusive transport have also been advanced.. |
| 178. |
Crystallinity control of sputtered ZnO films by utilizing buffer layers fabricated via nitrogen mediated crystallization: Effects of nitrogen flow rate
High quality ZnO:Al (AZO) films have been obtained by utilizing buffer layers fabricated via nitrogen mediated crystallization (NMC), where sputtering method is employed for preparation of both buffer layers and AZO films. Introduction of small amount of N2 (N2/(Ar+N2) = 16%) to the sputtering atmosphere of NMC-ZnO buffer layers drastically improves the crystallinity of buffer layers and thus AZO films. The most remarkable effect of the buffer layers is a significant reduction in the resistivity at high base pressure of background gases. The resistivity of conventional AZO films increases from 2.0 m??cm to 70.0 m??cm with increasing the base pressure from 3×10-5 Pa to 1×10-3 Pa, while the resistivity of AZO films with NMC buffer layers increases from 0.5 m??cm to 2.0 m??cm, where the thickness of AZO film is 88 nm. Furthermore, AZO films with a sheet resistance of 10 ?/? and an optical transmittance higher than 80% in a wide wavelength range of 400?1100 nm have been obtained.. |
| 179. |
Control of Deposition Profile and Properties of Plasma CVD Carbon Films
We have succeeded to deposit anisotropic and top surface deposition profile on substrates with trenches using H-assisted plasma CVD of Ar + H2 + C7H8 at a low substrate temperature of 100 oC. For the anisotropic deposition profile, carbon is deposited without being deposited on sidewall of trenches. For the top surface deposition profile, carbon is deposited at only top surface. The optical emission measurements and evaluation of deposition rate have revealed that a high flux of H atmos is the key to the deposition profile control. The mass density of the films and their Raman spectrum have shown that their structure is a-C:H.. |
| 180. |
Fabrication of highly stable a-Si:H PIN solar cells using cluster suppression method. |
| 181. |
Yeonwon Kim, Takeaki Matsunaga, Kenta Nakahara, Hyunwoong Seo, Kunihiro Kamataki, Giichiro Uchida, Naho Itagaki, Kazunori Koga, Masaharu Shiratani, Effects of nanoparticle incorporation on properties of microcrystalline films deposited using multi-hollow discharge plasma CVD, SURFACE & COATINGS TECHNOLOGY, 10.1016/j.surfcoat.2012.04.029, 228, S550-S553, 2013.08, We investigated the effects of incorporation of crystalline nanoparticles on properties of microcrystalline Si films deposited using multi-hollow discharge plasma CVD. Both photo and dark conductivity of films with nanoparticles are lower than the films without nanoparticles. Films with nanoparticles have higher photosensitivity than those of films without nanoparticles in a low crystallinity region. Microcrystalline films of high crystallinity and high photosensitivity are obtained only in a range of small volume fraction of nanoparticles under low dilution ratio, R = ([SiH4] + [H-2])/[SiH4]. Incorporation of small amount of nanoparticles into films strongly affects photo and dark conductivity of films. (C) 2012 Elsevier B.V. All rights reserved.. |
| 182. |
Tatsuya Urakawa, Hidehumi Matsuzaki, Daisuke Yamashita, Giichiro Uchida, Kazunori Koga, Masaharu Shiratani, Yuichi Setsuhara, Makoto Sekine, Masaru Hori, Mass density control of carbon films deposited by H-assisted plasma CVD method, SURFACE & COATINGS TECHNOLOGY, 10.1016/j.surfcoat.2012.10.002, 228, S15-S18, 2013.08, In order to obtain high density carbon films with keeping anisotropic deposition profile on trench substrates, we control mass density of carbon films deposited by a H-assisted plasma chemical vapor deposition (CVD) method by ion kinetic energy of ions irradiating on film surface during deposition. The highest mass density of 2.14 g/cm(3) is obtained for deposition under the ion energy of 75 eV and it is 1.4 times as high as that for the ion energy of 32 eV. We also have studied etching rate of these films using H-2 + N-2 discharge plasmas. The lowest etch rate of 1.8 nm/min is obtained for the ion energy of 75 eV and it is 2.8 times as low as that for the ion energy of 32 eV. Etching rate of carbon films decreases exponentially with increasing the mass density of carbon films. Control of ion energy is the key to obtain high mass density carbon films with keeping anisotropic deposition profile on trench substrates. (C) 2012 Elsevier B.V. All rights reserved.. |
| 183. |
Observation of nanoparticle growth process using a high speed camera
Time evolution of spatial profile of nanoparticle amount in low pressure reactive discharge plasmas have been measured to study effects of amplitude modulation of the plasmas on particle growth in the initial growth phase. Amplitude modulation of discharge voltage leads to oscillate nanoparticle amount and their spatial profile. Growth of nanoparticles is suppressed by increasing the AM frequency.. |
| 184. |
Kazunori Koga, Katsushi Nishiyama, Yasuhiko Morita, Giichiro Uchida, Daisuke Yamashita, Kunihiro Kamataki, Hyunwoong Seo, Naho Itagaki, Masaharu Shiratani, Naoko Ashikawa, Suguru Masuzaki, Kiyohiko Nishimura, Akio Sagara, Effects of DC substrate bias voltage on dust flux in the Large Helical Device, JOURNAL OF NUCLEAR MATERIALS, 10.1016/j.jnucmat.2013.01.154, 438, S727-S730, 2013.07, We measured the dependence of the collected flux of dust particles on the bias potential Delta phi with respect to ground in the Large Helical Device at the National Institute of Fusion Science. This is a first step toward developing a novel method for removing dust for fusion reactors based on applying a local bias potential. The collected dust particles were classified into two kinds: spherical carbon particles smaller than 300 nm and stainless-steel flakes smaller than 1 mu m. For Delta phi = -70 to +70 V, the flux of spherical particles increased exponentially with increasing Delta phi. The flux of flakes increased when Delta phi was increased from -70 V to +30 V and it decreased at higher Delta phi. These results suggest that this method is useful for removing carbon and metal dust particles from the shadow area of fusion devices using appropriate control of the local bias potential. (C) 2013 Elsevier B. V. All rights reserved.. |
| 185. |
Katsushi Nishiyama, Yasuhiko Morita, Giichiro Uchida, Daisuke Yamashita, Kunihiro Kamataki, Hyunwoong Seo, Naho Itagaki, Kazunori Koga, Masaharu Shiratani, Naoko Ashikawa, Suguru Masuzaki, Kiyohiko Nishimura, Akio Sagara, Sven Bornholdt, Holger Kersten, Discharge power dependence of carbon dust flux in a divertor simulator, JOURNAL OF NUCLEAR MATERIALS, 10.1016/j.jnucmat.2013.01.169, 438, S788-S791, 2013.07, In fusion devices, dust particles are generated due to plasma-wall interactions and may cause safety or operational problems. Therefore it is necessary to clarify the generation and transport mechanisms of dust particles. Here we have measured energy influx from H-2 plasmas toward a graphite target using a calorimetric probe and compared the results with the dust flux toward a dust collecting substrate set on the reactor wall. The dust flux decreases with increasing the energy influx. For the higher discharge power, the more number of dust particles tend to redeposit onto the graphite target due to the higher ion drag force and hence the dust flux toward the reactor wall becomes smaller. The results show that dust inventory depends strongly on energy influx to graphite divertor plates in fusion devices. (C) 2013 Elsevier B. V. All rights reserved.. |
| 186. |
H. Seo, Y. Wang, G. Uchida, K. Kamataki, N. Itagaki, K. Koga, M. Shiratani, Growth control of ZnO nano-rod with various seeds and photovoltaic application, J. Phys. : Conference Series (11th APCPST), 10.1088/1742-6596/441/1/012029, 441, 1, 012029, 2013.06. |
| 187. |
Shinya Iwashita, Edmund Schuengel, Julian Schulze, Peter Hartmann, Zoltan Donko, Giichiro Uchida, Kazunori Koga, Masaharu Shiratani, Uwe Czarnetzki, Transport control of dust particles via the electrical asymmetry effect: experiment, simulation and modelling, JOURNAL OF PHYSICS D-APPLIED PHYSICS, 10.1088/0022-3727/46/24/245202, 46, 24, 245202, 2013.06, The control of the spatial distribution of micrometre-sized dust particles in capacitively coupled radio frequency discharges is relevant for research and applications. Typically, dust particles in plasmas form a layer located at the sheath edge adjacent to the bottom electrode. Here, a method of manipulating this distribution by the application of a specific excitation waveform, i.e. two consecutive harmonics, is discussed. Tuning the phase angle theta between the two harmonics allows one to adjust the discharge symmetry via the electrical asymmetry effect (EAE). An adiabatic (continuous) phase shift leaves the dust particles at an equilibrium position close to the lower sheath edge. Their levitation can be correlated with the electric field profile. By applying an abrupt phase shift the dust particles are transported between both sheaths through the plasma bulk and partially reside at an equilibrium position close to the upper sheath edge. Hence, the potential profile in the bulk region is probed by the dust particles providing indirect information on plasma properties. The respective motion is understood by an analytical model, showing both the limitations and possible ways of optimizing this sheath-to-sheath transport. A classification of the transport depending on the change in the dc self-bias is provided, and the pressure dependence is discussed.. |
| 188. |
Hyunwoong Seo, Yuting Wang, Giichiro Uchida, Kunihiro Kamataki, Naho Itagaki, Kazunori Koga, Masaharu Shiratani, Analysis on the effect of polysulfide electrolyte composition for higher performance of Si quantum dot-sensitized solar cells, ELECTROCHIMICA ACTA, 10.1016/j.electacta.2013.02.026, 95, 43-47, 2013.04, Quantum dot-sensitized solar cell (QDSC) based on multiple exciton generation of QD has been expected to realize high efficiency. This work focused on Si QD instead of conventional QD materials because of their toxicity and scarcity. Si QDs were fabricated by multi-hollow discharge plasma chemical vapor deposition. General QDSCs use polysulfide electrolyte because it is suitable for stabilizing QDs and its redox reaction is the best as compared with other redox systems. The improvement of redox reaction which is one of the slowest reactions in the kinetic analysis is closely connected with the enhancement of performance. For the enhancement on the overall performance of Si QDSC, the performance dependence on electrolyte composition was investigated. The concentrations of Na2S and S were varied for the activation of redox reaction and KCl concentration was optimized for the improvement of electrolyte characteristics. Consequently, the best performance of Si QDSC was obtained with 1 M Na2S, 2 M S, and 0.4M KCl polysulfide electrolyte. (c) 2013 Elsevier Ltd. All rights reserved.. |
| 189. |
M. Shiratani, G. Uchida, K. Kamataki, H. Seo, N. Itagaki, K. Koga, Control of nanoparticle formation in reactive plasmas and its application to fabrication of green energy devices, Proc. 13th International Conference on Plasma Surface Engineering, 2, 26, 100-103, 2013.03. |
| 190. |
ナノ材料のプラズマプロセシングの研究の現状と将来
This paper reviews production of nanoparticles using low pressure reactive plasmas and its application to quantum dot sensitized solar cells. For the method, nanoparticles of several nm in size with a small size dispersion are produced in gas phase using reactive plasmas, and then the nanoparticles and radicals are co-deposited on a substrate. This method realizes one-step deposition of nanoparticle composite films in a controllable way.. |
| 191. |
Hyunwoong Seo, Yuting Wang, Giichiro Uchida, Kunihiro Kamataki, Naho Itagaki, Kazunori Koga, Masaharu Shiratani, The reduction of charge recombination and performance enhancement by the surface modification of Si quantum dot-sensitized solar cell, ELECTROCHIMICA ACTA, 10.1016/j.electacta.2012.09.087, 87, 213-217, 2013.01, Multiple exciton generation solar cell based on quantum dots has higher theoretical efficiency than single exciton generation solar cell. In this work, Si quantum dots with the diameter of 10 nm were fabricated by the multi-hollow discharge plasma chemical vapor deposition and applied to the quantum dot-sensitized solar cell. In this cell, there was considerable electron recombination with redox electrolyte in the Si-TiO2 network because of large Si particle size. For the reduction of recombination and the enhancement of performance, a barrier layer was introduced. Zinc nitrate hexahydrate (Zn(NO3)(2)center dot 6H(2)O) and zinc acetate dihydrate (Zn(CH3COO)(2)center dot H2O) were employed as precursors for surface modification. Consequently,short circuit current and open circuit voltage of the cells were increased by the surface modification with both precursors. The improvement was ascribed to the inhibition of electrons back transfer from TiO2 to the electrolyte by the barrier layer. This result clearly demonstrated that the surface modification with ZnO was advantageous for the performance enhancement. (C) 2012 Elsevier Ltd. All rights reserved.. |
| 192. |
Hyunwoong Seo, Yuting Wang, Muneharu Sato, Giichiro Uchida, Kunihiro Kamataki, Naho Itagaki, Kazunori Koga, Masaharu Shiratani, Improvement of Si Adhesion and Reduction of Electron Recombination for Si Quantum Dot-Sensitized Solar Cells, JAPANESE JOURNAL OF APPLIED PHYSICS, 10.7567/JJAP.52.01AD05, 52, 1, 01AD05, 2013.01, Quantum dots (QDs) based on multiple exciton generation have attracted much attention. They are capable of generating multiple electrons by single-photon absorption. Si is one of the good QD sources and its nontoxicity and abundance are advantageous for photovoltaics. In this work, Si QDs were fabricated by multihollow discharge plasma chemical vapor deposition, and they were applied to Si QD-sensitized solar cells. Their initial performance was poor because of the weak adhesion of Si and charge recombination. In this work, we solved these problems through the functionalization of Si QDs and a ZnO barrier. Functionalized Si QDs were more adsorbed on TiO2 with strengthened adhesion and the ZnO barrier prevented the contact between TiO2 and the redox electrolyte. Consequently, the improved adhesion and the reduced electron recombination led to the enhancement of overall photovoltaic characteristics. (C) 2013 The Japan Society of Applied Physics. |
| 193. |
Yeonwon Kim, Kosuke Hatozaki, Yuji Hashimoto, Giichiro Uchida, Kunihiro Kamataki, Naho Itagaki, Hyunwoong Seo, Kazunori Koga, Masaharu Shiratani, High Amount Cluster Incorporation in Initial Si Film Deposition by SiH4 Plasma Chemical Vapor Deposition, JAPANESE JOURNAL OF APPLIED PHYSICS, 10.7567/JJAP.52.01AD01, 52, 1, 01AD01, 2013.01, We have carried out in-situ measurements of Si cluster volume fraction in Si films during plasma chemical vapor deposition by using quartz crystal microbalances (QCM's) together with a cluster-eliminating filter. The cluster volume fraction in films is deduced from film deposition rates with and without Si clusters using QCM's. By employing this method we have revealed a depth profile of the Si cluster volume fraction. A high cluster volume fraction is observed in the initial phase of film deposition. This behavior is compared with time evolution of SiH center dot, Si-center dot emission intensities and their intensity ratio. (C) 2013 The Japan Society of Applied Physics. |
| 194. |
Iping Suhariadi, Koichi Matsushima, Kazunori Kuwahara, Koichi Oshikawa, Daisuke Yamashita, Hyunwoong Seo, Giichiro Uchida, Kunihiro Kamataki, Kazunori Koga, Masaharu Shiratani, Sven Bornholdt, Holger Kersten, Harm Wulff, Naho Itagaki, Effects of Hydrogen Dilution on ZnO Thin Films Fabricated via Nitrogen-Mediated Crystallization, JAPANESE JOURNAL OF APPLIED PHYSICS, 10.7567/JJAP.52.01AC08, 52, 1, 01AC08, 2013.01, Hydrogenated ZnO thin films have been successfully deposited on glass substrates via a nitrogen mediated crystallization (NMC) method utilizing RF sputtering. Here we aim to study the crystallinity and electrical properties of hydrogenated NMC-ZnO films in correlation with substrate temperature and H-2 flow rate. XRD measurements reveal that all the deposited films exhibit strongly preferred (001) orientation. The integral breadth of the (002) peak from the hydrogenated NMC-ZnO films is smaller than that of the conventional hydrogenated ZnO films fabricated without nitrogen. Furthermore, the crystallinity and surface morphology of the hydrogenated NMC-ZnO films are improved by increasing substrate temperature to 400 degrees C, where the smallest integral breadth of (002) 2 theta-omega scans of 0.83 degrees has been obtained. By utilizing the hydrogenated NMC-ZnO films as buffer layers, the crystallinity of ZnO:Al (AZO) films is also improved. The resistivity of AZO films on NMC-ZnO buffer layers decreases with increasing H-2 flow rate during the sputter deposition of buffer layers from 0 to 5 sccm. At a H-2 flow rate of 5 sccm, 20-nm-thick AZO films with low resistivity of 1.5 x 10(-3) Omega cm have been obtained. (C) 2013 The Japan Society of Applied Physics. |
| 195. |
Shinya Iwashita, Katsushi Nishiyama, Giichiro Uchida, Hyunwoong Seo, Naho Itagaki, Kazunori Koga, Masaharu Shiratani, Dust particle formation due to interaction between graphite and helicon deuterium plasmas, FUSION ENGINEERING AND DESIGN, 10.1016/j.fusengdes.2012.10.002, 88, 1, 28-32, 2013.01, The collection of dust particles using divertor simulation helicon plasmas has been carried out to examine dust formation due to the interaction between a graphite target and deuterium plasmas, which are planned to operate in the large helical device (LHD) at the Japanese National Institute for Fusion Science (NIFS). The collected dust particles are classified into three types: (i) small spherical particles below 400 nm in size, (ii) agglomerates whose primary particles have a size of about 10 nm, and (iii) large flakes above 1 mu m in size. These features are quite similar to those obtained through hydrogen plasma operation, indicating that the dust formation mechanisms due to the interaction between a carbon wall and a plasma of deuterium, which is the isotope of hydrogen, is probably similar to those of hydrogen. (c) 2012 Elsevier B.V. All rights reserved.. |
| 196. |
Tatsuya Urakawa, Ryuhei Torigoe, Hidefumi Matsuzaki, Daisuke Yamashita, Giichiro Uchida, Kazunori Koga, Masaharu Shiratani, Yuichi Setsuhara, Keigo Takeda, Makoto Sekine, Masaru Hori, H-2/N-2 Plasma Etching Rate of Carbon Films Deposited by H-Assisted Plasma Chemical Vapor Deposition, JAPANESE JOURNAL OF APPLIED PHYSICS, 10.7567/JJAP.52.01AB01, 52, 1, 01AB01(4pages), 2013.01, Etching resistance of carbon films deposited by plasma chemical vapor deposition (CVD) is one of the concerns to fabricate nanostructures using such carbon films as protective coating films and dummy films. We have carried out H-2/N-2 plasma etching of carbon films deposited by using an H-assisted plasma CVD method. The etching rate of carbon films decreases exponentially with increasing the mass density of carbon films from 1.51 to 2.27 g/cm(3). The mass density of carbon films is the key parameter to tune the etching resistance. (C) 2013 The Japan Society of Applied Physics. |
| 197. |
Sputter deposition of Epitaxial Zinc-Indium Oxynitride Films for Excitonic Transistors. |
| 198. |
Yeonwon Kim, Takeaki Matsunaga, Kenta Nakahara, Giichiro Uchida, Kunihiro Kamataki, Naho Itagaki, Hyunwoong Seo, Kazunori Koga, Masaharu Shiratani, Effects of crystalline nanoparticle incorporation on growth, structure, and properties of microcrystalline silicon films deposited by plasma chemical vapor deposition, THIN SOLID FILMS, 10.1016/j.tsf.2012.06.023, 523, 29-33, 2012.11, We investigated effects of incorporation of Si crystalline nanoparticles into microcrystalline Si films during their deposition on their growth, structure and properties using multi-hollow discharge plasma chemical vapor deposition. The films with nanoparticles show a lower (220) orientation ratio than those without nanoparticles, whereas both the films have nearly the same film thickness and crystallinity. The films with nanoparticles have inverted conical growth, while the films without nanoparticles have columnar growth. Nucleation density of the films with nanoparticles is higher than that of the films without nanoparticles. Both photo and dark conductivities of the films with nanoparticles tend to be lower than those without nanoparticles. Thus, incorporation of small amount of nanoparticles into microcrystalline Si film affects growth, structure and properties of the films. (C) 2012 Elsevier B. V. All rights reserved.. |
| 199. |
Kunihiro Kamataki, Kazunori Koga, Giichiro Uchida, Naho Itagaki, Daisuke Yamashita, Hidefumi Matsuzaki, Masaharu Shiratani, Control of radial density profile of nano-particles produced in reactive plasma by amplitude modulation of radio frequency discharge voltage, THIN SOLID FILMS, 10.1016/j.tsf.2012.07.059, 523, 76-79, 2012.11, We investigate uniformity of radial density profile of nano-particles in capacitively-coupled radio frequency discharge with an amplitude modulation (AM) of rf discharge voltage, by a two-dimensional laser light scattering method. Their densities at the center and that at the edge of the electrode increase by 3 and 24 times when the amplitude modulation level increases from 0 (without AM) to 30%. The uniformity of radial density profile of nano-particles is significantly improved by using the AM method. (C) 2012 Elsevier B. V. All rights reserved.. |
| 200. |
Satoshi Kitazaki, Kazunori Koga, Masaharu Shiratani, Nobuya Hayashi, Growth Control of Dry Yeast Using Scalable Atmospheric-Pressure Dielectric Barrier Discharge Plasma Irradiation, JAPANESE JOURNAL OF APPLIED PHYSICS, 10.1143/JJAP.51.11PJ02, 51, 11, 11PJ02(5pages), 2012.11, We have investigated the effects of plasma irradiation on the growth of dry yeast (Saccharomyces cerevisiae) using a scalable atmospheric-pressure dielectric barrier discharge (DBD) device. NO of 380 ppm, NO2 of 10 ppm and O-3 of 560 ppm were detected 1 mm below the discharges, which were produced by the DBD plasmas. DBD plasma irradiation of 10 to 100 s enhances the growth of yeast in the lag phase, whereas that of 120 and 150 s suppresses the growth. O-3, NO2, photons, and heat generated by the plasma irradiation are not responsible for the growth enhancement of the dry yeast. Plasma etching has little effect on the growth of dry yeast cells. NO plays a key role in the growth enhancement of dry yeast cells. (C) 2012 The Japan Society of Applied Physics. |
| 201. |
A. Tanaka, M. Hirata, M. Shiratani, K. Koga, Y. Kiyohara, Subacute pulmonary toxicity of copper indium gallium diselenide following intratracheal instillations into the lungs of rats, Journal of Occupational Health, 10.1539/joh.11-0164-OA, 54, 3, 187-195, 2012.06. |
| 202. |
Kazunari Kuwahara, Naho Itagaki, Kenta Nakahara, Daisuke Yamashita, Giichiro Uchida, Kunihiro Kamataki, Kazunori Koga, Masaharu Shiratani, High quality epitaxial ZnO films grown on solid-phase crystallized buffer layers, THIN SOLID FILMS, 10.1016/j.tsf.2011.10.136, 520, 14, 4674-4677, 2012.05, High quality epitaxial ZnO films on sapphire (110) plane have been fabricated on ZnO homo-buffer layers crystallized via solid-phase epitaxially (SPE). The SPE-ZnO films are fabricated by annealing of amorphous ZnON (a-ZnON) films deposited by RF magnetron sputtering. During annealing, the a-ZnON films are oxidized and converted to ZnO crystal. X-ray diffraction (XRD) analysis shows that the resultant films are epitaxially grown on the sapphire substrates. By using the SPE-ZnO films as homo-buffer layers, the ZnO films with high crystallinity, which are deposited by RF magnetron sputtering, are fabricated. The full width at half-maximum of XRD patterns for 20-omega and omega scan of (002) plane are 0.094 degrees and 0.12 degrees, respectively, being significantly small compared with 0.24 degrees and 0.55 degrees for the films without buffer layers. Thus utilizing SPE buffer layers is very promising to obtain epitaxial ZnO films with high crystallinity. (C) 2011 Elsevier B.V. All rights reserved.. |
| 203. |
H. Seo, Y. Wang, G. Uchida, K. Kamataki, N. Itagaki, K. Koga, M. Shiratani, The Optical Analysis and Application of Size-controllable Si Quantum Dots Fabricated by Multi-hollow Discharge Plasma Chemical Vapor Deposition, Mat. Res. Soc. Symp. Proc., 10.1557/opl.2012.890, 1426, 313-318, 2012.04. |
| 204. |
Y. Kim, K. Hatozaki, Y. Hashimoto, H. Seo, G. Uchida, K. Kamataki, N. Itagaki, K. Koga, M. Shiratani, In-situ Measurements of Cluster Volume Fraction in Silicon Thin Films Using Quartz Crystal Microbalances, Mat. Res. Soc. Symp. Proc., 10.1557/opl.2012.839, 1426, 307-311, 2012.04. |
| 205. |
K. Kamataki, Y. Morita, M. Shiratani, K. Koga, G. Uchida, N. Itagaki, In situ analysis of size distribution of nano-particles in reactive plasmas using two dimensional laser light scattering method, JOURNAL OF INSTRUMENTATION, 10.1088/1748-0221/7/04/C04017, 7, C04017, 2012.04, We have developed a simple in-situ method for measuring the size distribution (the mean size (mean diameter) and size dispersion) of nano-particles generated in reactive plasmas using the 2 dimensional laser light scattering (2DLLS) method. The principle of the method is based on thermal coagulation of the nano-particles, which occurs after the discharge is turned off, and the size and density of the nano-particles can then be deduced. We first determined the 2D spatial distribution of the density and size of the nano-particles in smaller particle size (a few nm) range than ones deduced from the conventional 2DLLS method. From this 2D dataset, we have for the first time been able to determine the size distribution of nano-particles generated in a reactive plasma without ex-situ measurements.. |
| 206. |
M. Shiratani, K. Hatozaki, Y. Hashimoto, Y. Kim, H. Seo, K. Kamataki, G. Uchida, N. Itagaki, K. Koga, Characteristics of stable a-Si:H Schottoky cells fabricated by suppressing cluster deposition, Mat. Res. Soc. Symp. Proc., 10.1557/opl.2012.1245, 1426, 377-382, 2012.04. |
| 207. |
S. Kitazaki, K. Koga, M. Shiratani, N. Hayashi, Rapid Growth of Radish Sprouts Using Low Pressure O2 Radio Frequency Plasma Irradiation, Mat. Res. Soc. Symp. Proc., 10.1557/opl.2012.966, 1469, ww02-08, 2012.04. |
| 208. |
Y. Akiyoshi, N. Hayashi, S. Kitazaki, K. Koga and M. Shiratani, Influence of Atmospheric Pressure Torch Plasma Irradiation on Plant Growth, Mat. Res. Soc. Symp. Proc., 10.1557/opl.2012.970, 1469, ww06-10, 2012.04. |
| 209. |
S. Kitazaki, K. Koga, M. Shiratani, N. Hayashi, Effects of Atmospheric Pressure Dielectric Barrier Discharge Plasma Irradiation on Yeast Growth, Mat. Res. Soc. Symp. Proc., 10.1557/opl.2012.969, 1469, ww06-08, 2012.04. |
| 210. |
I. Suhariadi, N. Itagaki, K. Kuwahara, K. Oshikawa, D. Yamashita, G. Uchida, K. Kamataki, K. Koga, K. Nakahara, M. Shiratani, ZnO:Al Thin Films with Buffer Layers Fabricated via Nitrogen Mediated Crystallization: Effects of N2/Ar Gas Flow Rate Ratio, Trans. Mater. Res. Soc. Jpn., 10.14723/tmrsj.37.165, 37, 2, 165-168, 2012.01, Effects of N2/Ar gas flow rate ratio on the crystallinity of sputtered ZnO films fabricated via nitrogen mediated crystallization (NMC) have been clarified. Introduction of small amount of N2?(N2/Ar = 4/20.5 sccm) drastically improves the crystal orientation and enlarges grain size of the NMC-ZnO films, where FWHM of XRD patterns for 2θ-ω and ω scan of (002) plane are 0.17° and 2.6°, respectively. A further increase in N2/Ar flow rate ratio deteriorates the crystallinity, since excess N atoms in the films disarrange the crystal structure of ZnO. Furthermore, ZnO:Al (AZO) films with high crystallinity have been successfully fabricated by utilizing the NMC-ZnO films deposited at N2/Ar = 4/20.5 sccm as buffer layers. 100-nm-thick AZO films with a resistivity of 6.8×10-4?Ωcm and an optical transmittance higher than 80% in a wide wavelength range of 500 nm to 1500 nm has been obtained.. |
| 211. |
Giichiro Uchida, Kosuke Yamamoto, Muneharu Sato, Yuki Kawashima, Kenta Nakahara, Kunihiro Kamataki, Naho Itagaki, Kazunori Koga, Masaharu Shiratani, Effect of Nitridation of Si Nanoparticles on the Performance of Quantum-Dot Sensitized Solar Cells, JAPANESE JOURNAL OF APPLIED PHYSICS, 10.1143/JJAP.51.01AD01, 51, 1, 01AD01, 2012.01, We developed Si quantum-dot (QD) sensitized solar cells using nitridated Si nanoparticle films. The Si/N content ratio of the Si nanoparticle films was combinatorially controlled in double multi-hollow discharge plasma chemical vapor deposition (CVD) process in a SiH4/H-2 and N-2 gas mixture. The short-circuit current density of Si OD sensitized solar cells increases by a factor of 1.3 with the nitridation of Si nanoparticles, and a high photon-to-current conversion efficiency of 40% was achieved at a short wavelength of 350 nm. (C) 2012 The Japan Society of Applied Physics. |
| 212. |
Kazunori Koga, Kenta Nakahara, Yeon-Won Kim, Takeaki Matsunaga, Daisuke Yamashita, Hidefumi Matsuzaki, Giichiro Uchida, Kunihiro Kamataki, Naho Itagaki, Masaharu Shiratani, Deposition of Cluster-Free B-doped Hydrogenated Amorphous Silicon Films Using SiH4+B10H14 Multi-Hollow Discharge Plasma Chemical Vapor Deposition, JAPANESE JOURNAL OF APPLIED PHYSICS, 10.1143/JJAP.51.01AD03, 51, 1, 01AD03, 2012.01, We have deposited cluster-free B-doped hydrogenated amorphous silicon (a-Si:H) films using a SiH4+B10H14 multi-hollow discharge plasma chemical vapor deposition (CVD) method. We have studied the dependence of the deposition rate, band gap, and conductivity of the films on the gas flow rate ratio R = [B10H14]/[SiH4]. The deposition rate for SiH4+B10H14 plasmas is 2-3 times as high as that for pure SiH4 plasmas. Optical emission spectroscopy (OES) measurements indicate that SiH3 radical generation rate remains nearly constant regardless of R. These results suggest that BxHy radicals enhance the surface reaction probability and/or sticking probability of SiH3, being the predominant deposition precursor. Cluster-free B-doped a-Si:H films have a wide band-gap energy of 1.8-2.0 eV and a conductivity as high as 5.0 x 10(-6) S/cm. These results demonstrate that cluster-free B-doped a-Si:H films deposited using SiH4+B10H14 multi-hollow discharge plasma CVD are promising as a p-layer of pin a-Si:H solar cells. (C) 2012 The Japan Society of Applied Physics. |
| 213. |
Kazunori Koga, Takeaki Matsunaga, Yeonwon Kim, Kenta Nakahara, Daisuke Yamashita, Hidefumi Matsuzaki, Kunihiro Kamataki, Giichiro Uchida, Naho Itagaki, Masaharu Shiratani, Combinatorial Deposition of Microcrystalline Silicon Films Using Multihollow Discharge Plasma Chemical Vapor Deposition, JAPANESE JOURNAL OF APPLIED PHYSICS, 10.1143/JJAP.51.01AD02, 51, 1, 01AD02, 2012.01, A high-pressure depletion method using plasma chemical vapor deposition (CVD) is often used to deposit hydrogenated microcrystalline silicon (pc-Si:H) films of a low defect density at a high deposition rate. To understand proper deposition conditions of pc-Si:H films for a high-pressure depletion method, Si films were deposited in a combinatorial way using a multihollow discharge plasma CVD method by which fluxes of H and SiH3 radicals and their flux ratio can be varied with the distance from the discharges. The higher gas pressure brings about the higher deposition rate, whereas the process window of device quality mu c-Si:H films becomes quite narrower for the higher gas pressure. (C) 2012 The Japan Society of Applied Physics. |
| 214. |
Satoshi Kitazaki, Kazunori Koga, Masaharu Shiratani, Nobuya Hayashi, Growth Enhancement of Radish Sprouts Induced by Low Pressure O-2 Radio Frequency Discharge Plasma Irradiation, JAPANESE JOURNAL OF APPLIED PHYSICS, 10.1143/JJAP.51.01AE01, 51, 1, 01AE01(4pages), 2012.01, We studied growth enhancement of radish sprouts (Raphanus sativus L.) induced by low pressure O-2 radio frequency (RF) discharge plasma irradiation. The average length of radish sprouts cultivated for 7 days after O-2 plasma irradiation is 30-60% greater than that without irradiation. O-2 plasma irradiation does not affect seed germination. The experimental results reveal that oxygen related radicals strongly enhance growth, whereas ions and photons do not. (C) 2012 The Japan Society of Applied Physics. |
| 215. |
K. Koga, T. Urakawa, G. Uchida, H. Seo, K. Kamataki, N. Itagaki, M. Shiratani, Y. Setsuhara, M. Sekine, M. Hori, Self-organized carbon Mk formation on the top surface of fine trenches using a low temperature plasma anisotropic CVD for depositing fine organic structure, Proc. Plasma Conf. 2011, 23G03, 2011.11. |
| 216. |
Y. Wang, M. Sato, H. Seo, G. Uchida, N. Itagaki, K. Koga, M. Shiratani, Performance enhancement of Si quantum dot-sensitized solar cells by surface modification using ZnO barrier layer, Proc. Intern. Symp. on Dry Process, 33, 133-134, 2011.11. |
| 217. |
K. Hatozaki, K. Nakahara, T. Matsunaga, G. Uchida, H. Seo, N. Itagaki, K. Koga, M. Shiratani, Deposition of highly stable cluster-free a-Si:H films using fast gas flow multi-hollow discharge plasma CVD method, Proc. Plasma Conf. 2011, 24P016-O, 2011.11. |
| 218. |
K. Hatozaki, K. Nakahara, G. Uchida, K. Koga, M. Shiratani, Stable schottky solar cells using cluster-free a-si:h prepared by multi-hollow discharge plasma CVD, Proc. PVSEC-21, 3D-2P-18, 2011.11. |
| 219. |
M. Sato, Y. Wang, K. Nakahara, T. Matsunaga, H. Seo, G. Uchida, K. Koga, M. Shiratani, Quantum dot-sensitized solar cells using nitridated si nanoparticles produced by double multi-hollow discharges, Proc. PVSEC-21, 3D-5P-12, 2011.11. |
| 220. |
T. Urakawa, H. Matsuzaki, D. Yamashita, G. Uchida, K. Koga, M. Shiratani, Y. Setsuhara, M. Sekine, M. Hori, Optical emission spectroscopy of Ar+H2+ C7H8 discharges for anisotropic plasma CVD of carbon, Proc. Intern. Symp. on Dry Process, 33, 123-124, 2011.11. |
| 221. |
N. Hayashi, Y. Akiyoshi, S. Kitazaki, K. Koga, M. Shiratani, Influence of active oxygen species produced by atmospheric torch plasma on plant growth, Proc. Intern. Symp. on Dry Process, 33, 135-136, 2011.11. |
| 222. |
T. Mieno, K. Koga, M. Shiratani, Production Process of Carbon Nanotube Coagulates, Proc. Plasma Conf. 2011, 24F08, 2011.11. |
| 223. |
S. Kitazaki, K. Koga, M. Shiratani, N. Hayashi, Growth promotion characteristics of bread yeast by atmospheric pressure dielectric barrier discharge plasma irradiation, Proc. Plasma Conf. 2011, 23P018-O, 2011.11. |
| 224. |
T. Urakawa, H. Matsuzaki, D. Yamashita, G. Uchida, K. Koga, M. Shiratani, Y. Setsuhara, M. Sekine, M. Hori, Effects of substrate bias voltage on plasma anisotropic CVD of carbon using H-assisted plasma CVD reactor, Proc. Plasma Conf. 2011, 24P007-O, 2011.11. |
| 225. |
M. Sato, Y. Wang, K. Nakahara, T. Matsunaga, H. Seo, G. Uchida, K. Koga and M. Shiratani, Deposition of FeSi2 nano-particle film, Proc. Plasma Conf. 2011, 24P009-O, 2011.11. |
| 226. |
G. Uchida, K. Yamamoto, Y. Kawashima, M. Sato, K. Nakahara, K. Kamataki, N. Itagaki, K. Koga, M. Kondo, M. Shiratani, Surface nitridation of silicon nano-particles using double multi-hollow discharge plasma CVD, Physica Status Solidi (c), 10.1002/pssc.201001230, 8, 10, 3017-3020, 2011.10. |
| 227. |
Kunihiro Kamataki, Hiroshi Miyata, Kazunori Koga, Giichiro Uchida, Naho Itagaki, Masaharu Shiratani, Impacts of Amplitude Modulation of RF Discharge Voltage on the Growth of Nanoparticles in Reactive Plasmas, APPLIED PHYSICS EXPRESS, 10.1143/APEX.4.105001, 4, 10, 105001, 2011.10, We have investigated the effects of plasma fluctuation on the growth of nanoparticles in capacitively-coupled rf discharges with amplitude modulation (AM). Nanoparticles grow more slowly for higher AM levels, which causes the density of nanoparticles to increase by 100% and their size to decrease by 23%. The increase in the number of radicals for nucleation and nanoparticles by AM is thought to cause a decrease in the radical flux for a nanoparticle because the rate of increase in the number of radicals is smaller than that of nanoparticles. Therefore, this causes the generation of a large amount of nanoparticles with small sizes. (C) 2011 The Japan Society of Applied Physics. |
| 228. |
G. Uchida, Y. Kawashima, K. Yamamoto, M. Sato, K. Nakahara, T. Matsunaga, D. Yamashita, H. Matsuzaki, K. Kamataki, N. Itagaki, K. Koga, M. Kondo, M. Shiratani, Hybrid sensitized solar cells using Si nanoparticles and ruthenium dye, Physica Status Solidi (c), 10.1002/pssc.201100166, 8, 10, 3021-3024, 2011.10. |
| 229. |
K. Koga, K. Nakahara, Y. Kim, Y. Kawashima, T. Matsunaga, M. Sato, D. Yamashita, H. Matsuzaki, G. Uchida, K. Kamataki, N. Itagaki, and M. Shiratani, Deposition of cluster-free P-doped a-Si:H films using SiH4+PH3 multi-hollow discharge plasma CVD method, Physica Status Solidi (c), 10.1002/pssc.201100229, 8, 10, 3013-3016, 2011.10. |
| 230. |
Kazunori Koga, Takeaki Matsunaga, William Makoto Nakamura, Kenta Nakahara, Yuuki Kawashima, Giichiro Uchida, Kunihiro Kamataki, Naho Itagaki, Masaharu Shiratani, Comparison between silicon thin films with and without incorporating crystalline silicon nanoparticles into the film, THIN SOLID FILMS, 10.1016/j.tsf.2011.01.408, 519, 20, 6896-6898, 2011.08, We have deposited Si thin films using a multi-hollow discharge plasma CVD method to compare properties of the films with and without incorporating crystalline Si nanoparticles into the films. After the deposition of the films, we have evaluated crystallization of the films by irradiating laser. We have found that a laser power at which crystalline Si nanoparticles embedded a-Si:H films start to be crystallized is lower than that for a-Si:H films without the nanoparticles. The incorporation of the nanoparticles has no effect on the defect density of the films. These results suggest incorporation of crystalline Si nanoparticles into the films play a role of crystallization of Si films during the deposition. (C) 2011 Elsevier B.V. All rights reserved.. |
| 231. |
Nobuya Hayashi, Akari Nakahigashi, Masaaki Goto, Satoshi Kitazaki, Kazunori Koga, Masaharu Shiratani, Redox Characteristics of Thiol Compounds Using Radicals Produced by Water Vapor Radio Frequency Discharge, JAPANESE JOURNAL OF APPLIED PHYSICS, 10.1143/JJAP.50.08JF04, 50, 8, 08JF04, 2011.08, The redox reaction between cystein and cystine is observed using radicals produced in water vapor plasma for the control of plant growth. Cystein is oxidized to cystine using the OH radical in the higher-pressure regime and cystine is reduced to cystein by the H radical generated in the lower-pressure regime. Also, the oxidative stress reaction of plants is observed when water vapor plasma is irradiated onto seeds of plants such as radish sprouts. The mechanism of the control of plant growth is explained by the change in thiol compound quantity of the plant cells induced by the radical reaction. (C) 2011 The Japan Society of Applied Physics. |
| 232. |
T. Urakawa, T. Nomura, H. Matsuzaki, D. Yamashita, G. Uchida, K. Koga, M. Shiratani, Y. Setsuhara, M. Sekine, M. Hori, Deposition profile control of carbon films on submicron wide trench substrate using H-assisted plasma CVD, Proc. of The 20th International Symposium on Plasma Chemistry （ISPC20）, POL02, 2011.07. |
| 233. |
Masaharu Shiratani, Kazunori Koga, Shinya Iwashita, Giichiro Uchida, Naho Itagaki, Kunihiro Kamataki, Nano-factories in plasma: present status and outlook, JOURNAL OF PHYSICS D-APPLIED PHYSICS, 10.1088/0022-3727/44/17/174038, 44, 17, 174038, 2011.05, We propose the concept of 'nano-factory in plasma' which is a miniature version of a macroscopic conventional factory. A nano-factory in plasma produces nanoblocks and radicals (adhesives) in reactive plasmas, transports nanoblocks towards a substrate and arranges them on the substrate. We describe several key control methods for a nano-factory in plasma: size and structure control of nanoparticles, control of their agglomeration, transport and sticking, and then explain the combination of several types of control. Finally we point out remaining important issues in nano-factories in plasma.. |
| 234. |
K. Koga, G. Uchida, K. Yamamoto, Y. Kawashima, M. Sato, K. Kamataki, N. Itagaki, M. Shiratani, Generation and Surface Modification of Si nano-particles using SiH4/H2 and N2 multi-hollow discharges and their application to the third generation photovoltaics, International Conference on Advances in Condensed and Nano Materials (ICACNM), 10.1063/1.3653600, 1393, 27-30, 2011.02. |
| 235. |
Zno films with buffer layers crystallized via nitrogen mediation: Effects of deposition temperature of buffer layers. |
| 236. |
Zinc oxide-based transparent conducting films with buffer layers fabricated via nitrogen-mediated crystallization. |
| 237. |
Properties and performance of si quantum dot-sensitized solar cells with low temperature titania paste. |
| 238. |
Effects of nano-particles on (220) crystal orientation of microcrystallite silicon thin films. |
| 239. |
Defect density of cluster-free a-si:h films deposited by multi-hollow discharge plasma CVD. |
| 240. |
Combinatorial study on effects of substatrate temperature of silicon film deposition using multi-hollow discharge plasma cvd. |
| 241. |
Study of interaction between plasma fluctuation and nucleation of nanoparticle in plasma CVD
We have investigated effects of plasma fluctuation on the growth of nanoparticles in capacitively-coupled rf discharges with amplitude modulation. Nanoparticles grow more slowly for higher AM levels, that is they have 7 times higher density and 23% smaller size. This AM method is useful for the production of a large amount of nanoparticles with a small size. |
| 242. |
Radical Flux Evaluation to Microcrystalline Silicon Films Deposited by Multi-Hollow Discharge Plasma CVD
To evaluate radical fluxes for microcrystalline silicon film deposition, Si films were deposited in a combinatorial way using a multi-hollow discharge plasma CVD method. Film crystallinity varied with the distance from the powered electrode. Based on the film deposition rate and Raman crystallinity, we proposed a method to estimate hydrogen flux. This evaluation of hydrogen flux is one of useful way to understand a process window of ?c-Si:H films.. |
| 243. |
Low resistive ZnO:Al films with ZnO buffer layers fabricated by Ar/N2 magnetron sputtering
Low resistive ZnO:Al (AZO) films with uniform spatial distribution have been obtained by utilizing buffer layers fabricated by Ar/N2 magnetron sputtering. For 100 nm-thick AZO films, the averaged grain size of AZO films with buffer layers is 65 nm, which is 1.8 times larger than that of the films without buffer layers. This increase in the grain size of AZO films is due to the low grain density of buffer layers. As a result, the resistivity is drastically reduced. At the area facing the target erosion, the resistivity reduced from 2.27 m??cm for the films without buffer layers to 0.50 m??cm for our films, consequently, the spatial distribution of the resistivity is significantly improved. These results reveal that our method described here is full of promise for fabrication of ZnO-based TCO materials.. |
| 244. |
Influence of nano-particles on multi-hollow discharge plasma for microcrystalline silicon thin films deposition
Effects of nano-particles on formation kinetics of microcrystalline silicon films were studied by X-ray diffraction spectroscopy (XRD) and optical emission spectroscopy (OES). Volume fraction of (220) orientation crystals of films without incorporating nano-particles is higher than that of those with nano-particles. The IH?/ISi* value in the region with nano-particles is slightly higher than that in the region without nano-particles. The ISi*/ISiH* value is almost the same as that in the region with and without nano-particles. These results suggest that (220) orientation crystal growth is suppressed by incorporation of nano-particles.. |
| 245. |
Effects of nanoparticle incorporation on Si thin films deposited by plasma CVD
We have investigated effects of nanoparticle inclusion on properties of a-Si:H films and mc-Si:H films using the multi-hollow discharge plasma CVD method. Minor deposition species (nanoparticles in this study) modify considerably properties of a-Si:H films and mc-Si:H films. |
| 246. |
Effects of N2 gas addition to sputtering plasma on properties of epitaxial ZnO films
Effects of N2/Ar flow rate ratio on properties of ZnO films fabricated via nitrogen mediated crystallization (NMC) have been studied. NMC-ZnO films are deposited by RF magnetron sputtering using Ar-N2 mixed gas. X-ray diffraction (XRD) analysis shows that the crystallinity of NMC-ZnO films is improved by addition of a small amount of N2 to sputtering atmosphere (N2/(Ar+N2) flow ratio of 8%). By using the NMC-ZnO films as homo-buffer layers, ZnO films with high crystallinity are deposited by RF magnetron sputtering. The full width at half-maximum of XRD patterns for ω scan of (002) plane are 0.061°, being significantly small compared with 0.49° for the films without buffer layers. A further increase in N2/Ar flow rate ratio deteriorates the crystallinity because excess N atoms in the films disarrange the crystal structure of ZnO. The results indicate that utilizing NMC buffer layers deposited at an adequate N2 partial pressure is very promising to obtain epitaxial ZnO films with high crystallinity.. |
| 247. |
Effects of electrolyte on performance of quantum dot-sensitized solar cells using Si nanoparticles synthesized by multi-hollow discharge plasma CVD
Effects of electrolyte on performance of Si QDSCs were investigated. We successfully fabricated an efficient polysulfide electrolyte based on the solvent mixed with water and methanol at a volume ratio of 3:7. The optimal electrolyte contains 1.0M Na2S, 0.5M S and 0.2M KCl. By introducing different ingredients with proper concentration, Jsc, Voc and fill factor are much improved. The efficiency of Si QDSCs using optimized electrolyte is 0.027%. |
| 248. |
Deposition of cluster-free a-Si:H films using cluster eliminating filter
We have succeeded in deposition of highly stable a-Si:H films at a rate of 3 nm/s. To evaluate their performance as an I layer of PIN solar cells, Fill Factor (FF) of N-type c-Si/a-Si:H/Ni Schottky cells with cluster free a-Si:H films were measured. High quality stable a-Si:H films, were deposited with a multi-hollow discharge plasma CVD reactor together with a cluster-eliminating filter. Initial FF of the cell is 0.521, whereas stabilized FF is 0.495 that is 4.99% lower than the initial FF. Our multi-hollow discharge plasma CVD method is useful to fabricate highly stable a-Si:H solar cells.. |
| 249. |
Collection of carbon dust particles formed due to plasma-wall interactions between high density H2 plasma and carbon wall onto substrates by applying local DC bias voltage
We collected dust particles generated by interaction between a plasma and a carbon target in helicon discharge reactor, by which diverter plasmas in fusion devices are simulated. The dust particles are classified into three kinds: small spherical particles, agglomerates, and large flakes, suggesting three formation mechanisms: chemical vapor deposition (CVD) growth, agglomeration, and peeling from redeposited layer on the reactor wall. The area density and flux towards substrates of dust particles exponentially increase with the substrate bias voltage. The energy influx of plasmas towards the target and ion density were measured to clarify the dust formation mechanisms. They are nearly constant irrespective of the substrate bias voltage suggesting that the production rate of dust particles does not depend on the substrate bias voltage and their collection efficiency does.. |
| 250. |
Impacts of Plasma Fluctuations on Growth of Nano-Particles in Reactive Plasma. |
| 251. |
Combinatorial study of substrate temperature dependence on properties of silicon films deposited using multihollow discharge plasma CVD
A combinatorial technique using a multi-hollow discharge plasma CVD method has been employed to investigate effects of substrate temperature on hydrogenated microcrystalline silicon (?c-Si:H) film growth. No film is deposited near the discharge region RT to 350°C, whereas the area of no film region decreases with increasing the substrate temperature. This is attributed to competitive reactions between Si etching by H atoms and Si deposition. The area of microcrystalline Si region increases with the substrate temperature due to high surface diffusion rate of Si containing radical. These results show that the process window of μc-Si:H films becomes wider for the higher substrate temperature due to two reasons: 1) the lower Si etching rate and 2) the longer surface migration length of Si containing radicals. The defect density decreases significantly with increasing Ts from 6.24 × 10 16 cm -3 for Ts =100 o C down to 6.26 × 10 15 cm -3 for T s =300 o C.. |
| 252. |
Naho Itagaki, Kazunari Kuwahara, Kenta Nakahara, Daisuke Yamashita, Giichiro Uchida, Kazunori Koga, Masaharu Shiratani, Highly Conducting and Very Thin ZnO:Al Films with ZnO Buffer Layer Fabricated by Solid Phase Crystallization from Amorphous Phase, APPLIED PHYSICS EXPRESS, 10.1143/APEX.4.011101, 4, 1, 011101-011101-3 , 2011.01, We propose a novel method of oxide crystal growth via atomic-additive mediated amorphization. By utilizing this method, solid-phase crystallization (SPC) of ZnO from amorphous phase has been successfully demonstrated via nitrogen atom mediation. The resultant SPC-ZnO films are highly orientated and the crystallinity is higher than that of the films prepared by conventional sputtering. By using the SPC-ZnO as a buffer layer, the resistivity of ZnO:Al (AZO) films is drastically decreased. 20-nm-thick AZO films with a resistivity of 5 x 10(-4) Omega cm and an optical transmittance higher than 80% in a wide wavelength range of 400-2500 nm have been obtained. (C) 2011 The Japan Society of Applied Physics. |
| 253. |
William Makoto Nakamura, Hidefumi Matsuzaki, Hiroshi Sato, Yuuki Kawashima, Kazunori Koga, Masaharu Shiratani, High rate deposition of highly stable a-Si:H films using multi-hollow discharges for thin films solar cells, SURFACE & COATINGS TECHNOLOGY, 10.1016/j.surfcoat.2010.07.081, 205, S241-S245, 2010.12, We developed a multi-hollow discharge plasma chemical vapor deposition (CVD) method to deposit a-Si:H films of high stability against light exposure for solar cell applications. This method suppresses incorporation of clusters, which are formed in discharges, into films; and such a-Si:H films without cluster incorporation show high stability against light exposure. Aiming at increasing the deposition rate, we have developed a honeycomb type electrode with more than double number of holes, and we have realized deposition of highly stable a-Si:H films of 4.7 x 10(15) cm(-3) in stabilized defect density at a rate of 3.0 nm/s and better film thickness uniformity within 5% in an area of 4 cm in diameter. (C) 2010 Elsevier B.V. All rights reserved.. |
| 254. |
High rate deposition of cluster-suppressed amorphous silicon films deposited using a multi-hollow discharge plasma CVD
We have examined effects of gas velocity and gas pressure on a deposition rate of hydrogenated amorphous silicon (a-Si:H) films and on a volume fraction of clusters in the films using a multi-hollow discharge plasma CVD method. The maximum deposition rate realized for each pressure exponentially increases with decreasing the pressure from 1.0 Torr to 0.1 Torr, whereas the volume fraction of clusters very slightly increases with increasing the deposition rate. Based on the results, we have succeeded in depositing highly stable a-Si:H films of 4.9 × 1015cm-3 in a stabilized defect density at a rate of 3.0nm/s using the method. © 2010 Materials Research Society.. |
| 255. |
Redox reaction and plant growth stimulation using low pressure plasmas. |
| 256. |
M. Shiratani, K. Koga, G. Uchida, N. Itagaki, K. Kamataki, Fluctuation Control for Plasma Nanotechnologies, Proc. IEEE TENCON 2010, 10.1109/TENCON.2010.5685920, XII-XVI , 2010.11, プラズマナノテクノロジーで最重要課題となっている揺らぎの制御に関する現状と将来を展望した論文。. |
| 257. |
G. Uchida, S. Nunomutra, H. Miyata, S. Iwashita, D. Yamashita, H. Matsuzaki, K. Kamataki, N. Itagaki, K. Koga, M. Shiratani, Effects of Ar addition on breakdown voltage in a Si(CH3)2(OCH3)2 RF discharge, Proc. IEEE TENCON 2010, 10.1109/TENCON.2010.5686704, 2199-2201, 2010.11. |
| 258. |
K. Kamataki, H. Miyata, K. Koga, G. Uchida, N. Itagaki, D. Yamashita, H. Matsuzaki, M. Shiratani, Effects of Amplitude Modulation of rf Discharge Voltage on Growth of Nano-Particles in Reactive Plasma, Proc. IEEE TENCON 2010, 10.1109/TENCON.2010.5686456, 1943-1947, 2010.11. |
| 259. |
T. Matsunaga, Y. Kawashima, K. Koga, K. Nakahara, W. M. Nakamura, G. Uchida, N. Itagaki, D. Yamashita, H. Matsuzaki, M. Shiratani, Deposition profiles of microcrystalline silicon films using multi-hollow discharge plasma CVD, Proc. IEEE TENCON 2010, 10.1109/TENCON.2010.5686679 , 2219-2212, 2010.11. |
| 260. |
K. Nakahara, Y. Kawashima, M. Sato, T. Matsunaga, K. Yamamoto, W. M. Nakamura, D. Yamashita, H. Matsuzaki, G. Uchida, N. Itagaki, K. Koga, M. Shiratani, Cluster-Free B-Doped a-Si:H Films Deposited Using SiH4 + B10H14 Multi-Hollow Discharges, Proc. IEEE TENCON 2010, 10.1109/TENCON.2010.5686686, 2216-2218, 2010.11. |
| 261. |
T. Nomura, T. Urakawa, Y. Korenaga, D. Yamashita, H. Matsuzaki, K. Koga, M. Shiratani, Substrate temperature dependence of feature profile of carbon films on substrate with submicron trenches, Proc. IEEE TENCON 2010, 10.1109/TENCON.2010.5686688, 2213-2215, 2010.11. |
| 262. |
Y. Akiyoshi, A. Nakahigashi, N. Hayashi, S. Kitazaki, Takuro Iwao, K. Koga, M. Shiratani, Redox Characteristics of Amino Acids Using Low Pressure Water Vapor RF Plasma, Proc. IEEE TENCON 2010, 10.1109/TENCON.2010.5686467, 1957-1959, 2010.11. |
| 263. |
Y. Kawashima, K. Yamamoto, M. Sato, T. Matsunaga, K. Nakahara, D. Yamashita, H. Matsuzaki, G. Uchida, K. Koga, M. Shiratani, Photoluminescence of Si nanoparticles synthesized using multi-hollow discharge plasma CVD, Proc. IEEE TENCON 2010, 10.1109/TENCON.2010.5686677, 2222-2224, 2010.11. |
| 264. |
S. Kitazaki, D. Yamashita, H. Matsuzaki, G. Uchida, K. Koga, M. Shiratani, Growth Stimulation of Radish Sprouts Using Discharge Plasma, Proc. IEEE TENCON 2010, 10.1109/TENCON.2010.5686474, 1960-1963, 2010.11. |
| 265. |
K. Nakahara, Y. Kawashima, M. Sato, T. Matsunaga, K. Yamamoto, W. M. Nakamura, D. Yamashita, H. Matsuzaki, G. Uchida, K. Kamataki, N. Itagaki, K. Koga, M. Shiratani, Deposition rate enhancement of cluster-free P-doped a-Si:H films using multi-hollow discharge plasma CVD method, Proc. of 63rd Annual Gaseous Electronics Conference and 7th International Conference on Reactive Plasma, 55, 7, CTP.00087, 2010.10. |
| 266. |
T. Matsunaga, Y. Kawashima, K. Koga, W. M. Nakamura, K. Nakahara, H. Matsuzaki, D. Yamashita, G. Uchida, K. Kamataki, N. Itagaki, M. Shiratani, Combinatorial deposition of microcrystalline Si films using multi-hollow discharge plasma CVD, Proc. of 63rd Annual Gaseous Electronics Conference and 7th International Conference on Reactive Plasma, 55, 7, CTP.00089, 2010.10. |
| 267. |
A. Nakahigashi, Y. Akiyoshi, N. Hayashi, S. Kitazaki, K. Koga, M. Shiratani, Redox Characteristics of Thiol of Plants Using Radicals Produced by RF Discharge, Proc. of 63rd Annual Gaseous Electronics Conference and 7th International Conference on Reactive Plasma, 55, 7, KWP.00008, 2010.10. |
| 268. |
T. Nomura, T. Urakawa, Y. Korenaga, D. Yamashita, H. Matsuzaki, K. Koga, M. Shiratani, Y. Setsuhara, M. Sekine, M. Hori, Plasma parameter measurements of Ar+H2+C7H8 plasma in H-assisted plasma CVD reactor, Proc. of 63rd Annual Gaseous Electronics Conference and 7th International Conference on Reactive Plasma, 55, 7, DTP.00173, 2010.10. |
| 269. |
Kazunori Koga, Masaharu Shiratani, Yukio Watanabe, Deposition of a-Si: H Films with High Stability against Light Exposure by Reducing Deposition of Nanoparticles Formed in SiH4 Discharges, Industrial Plasma Technology: Applications from Environmental to Energy Technologies, 10.1002/9783527629749.ch20, 247-257, 2010.10. |
| 270. |
Shinya Iwashita, Hiroshi Miyata, Kazunori Koga, Masaharu Shiratani, Nanoblock Assembly Using Pulse RF Discharges with Amplitude Modulation, Industrial Plasma Technology: Applications from Environmental to Energy Technologies, 10.1002/9783527629749.ch31, 377-383, 2010.10. |
| 271. |
Y. Kawashima, K. Nakahara, H. Sato, K. Koga, M. Shiratani, M. Kondo, Quantum dot-sensitized solar cells using Si nanoparticles, Trans. Mateｒ. Res. Soc. Jpn., 35, 3, 597-599, 2010.09. |
| 272. |
Deposition profile control of carbon films on patterned substrates using a hydrogen-assisted plasma CVD method
We have studied effects of H atom source on deposition profiles of carbon films, deposited by H assisted anisotropic plasma CVD method. Deposition rate normalized by that for the aspect ratio of 1 at sidewall and bottom decreases with increasing discharge power of H atom source from 0 W to 500 W, because the incident H atom flux per surface area in a trench increases and H atoms etch carbon films. © 2010 Materials Research Society.. |
| 273. |
Y. Kawashima, K. Yamamoto, M. Sato, K. Nakahara, T. Matsunaga, W. M. Nakamura, D. Yamashita, H. Matsuzaki, G. Uchida, K. Kamataki, N. Itagaki, K. Koga, M. Shiratani, M. Kondo, Si quantum dot-sensitized solar cells using Si nanoparticles produced by plasma CVD, Proc. 35th IEEE Photovoltaic Specialists Conf., 10.1109/PVSC.2010.5617205, 3347-3351, 2010.07. |
| 274. |
K. Nakahara, Y. Kawashima, M. Sato, T. Matsunaga, K. Yamamoto, W. M. Nakamura, D. Yamashita, H. Matsuzaki, G. Uchida, K. Kamataki, N. Itagaki, K. Koga, M. Shiratani, Deposition of cluster-free P-doped a-Si:H films using a multi-hollow discharge plasma CVD method, Proc. 35th IEEE Photovoltaic Specialists Conf., 10.1109/PVSC.2010.5616514, 3722-3755, 2010.07. |
| 275. |
K. Koga, Y. Kawashima, K. Nakahara, T. Matsunaga, W. M. Nakamura, M. Shiratani, Effects of hydrogen dilution on electron density in multi-hollow discharges with magnetic field for A-Si:H film deposition, Proc. 35th IEEE Photovoltaic Specialists Conf., 10.1109/PVSC.2010.5616502, 3718-3721, 2010.07. |
| 276. |
Akiyo Tanaka, Miyuki Hirata, Yutaka Kiyohara, Makiko Nakano, Kazuyuki Omae, Masaharu Shiratani, Kazunori Koga, Review of pulmonary toxicity of indium compounds to animals and humans, THIN SOLID FILMS, 10.1016/j.tsf.2009.10.123, 518, 11, 2934-2936, 2010.03, Due to the increased production of ITO, the potential health hazards arising from occupational exposure to this material have attracted much attention. This review consists of three parts: 1) toxic effects of indium compounds on animals, 2) toxic effects of indium compounds on humans, and 3) recommendations for preventing exposure to indium compounds in the workplace.
Available data have indicated that insoluble form of indium compounds, such as ITO, indium arsenide (InAs) and indium phosphide (InP), can be toxic to animals. Furthermore, InP has demonstrated clear evidence of carcinogenic potential in long-term inhalation studies using experimental animals. As for the dangers to humans, some data are available concerning adverse health effects to workers who have been exposed to indium-containing particles. The Japan Society for Occupational Health recommended the value of 3 mu g/L of indium in serum as the occupational exposure limit based on biological monitoring to preventing adverse health effects in workers resulting from occupational exposure to indium compounds. Accordingly, it is essential that much greater attention is focused on human exposure to indium compounds, and precautions against possible exposure to indium compounds are most important with regard to health management among indium-handling workers. (C) 2009 Elsevier B.V. All rights reserved.. |
| 277. |
Y. Kawashima, K. Nakahara, H. Sato, K. Koga, M. Shiratani, M. Kondo, Synthesis of crystalline Si nanoparticles for Quantum dots-sensitized solar cells using multi-hollow discharge plasma CVD, Proc. of the 27th symposium on plasma processing, B5-05, 101-102, 2010.02. |
| 278. |
S. Iwashita, H. Miyata, YasuY. Yamada, H. Matsuzaki, K. Koga, M. Shiratani, Observation of nano-particle transport in capacitively coupled radio frequency discharge plasma, Proc. of the 27th symposium on plasma processing, P1-13, 153-154, 2010.02. |
| 279. |
H. Sato, Y. Kawashima, K. Nakahara, K. Koga, M. Shiratani, Measurement of electron density in multi-hollow discharges with magnetic field, Proc. of the 27th symposium on plasma processing, A6-01, 105-106, 2010.02. |
| 280. |
H. Miyata, S. Iwashita, YasuY. Yamada, K. Koga, M. Shiratani, N. Ashikawa, S. Muzaki, K. Nishimura, A. Sagara, LHD Experimental Group, In-Situ Sampling of Dust Particles Produced Due to Interaction between Main Discharge Plasma and Inner Wall in LHD, Proc. of the 27th symposium on plasma processing, P1-14, 155-156, 2010.02. |
| 281. |
T. Mieno, GuoDong Tan, S. Usuba, K. Koga, M. Shiratani, In-situ Measurement of Production Process of Nanotube-Aggregates by the Laser-Mie Scattering (Dependence of Arc Condition and Gravity), Proc. of the 27th symposium on plasma processing, P2-17, 257-258, 2010.02. |
| 282. |
K. Koga, H. Sato, Y. Kawashima, W. M. Nakamura, M. Shiratani, Effects of gas residence time and H2 dilution on electron density in multi-hollow discharges of SiH4+ H2, Proc. of the 27th symposium on plasma processing, A5-06, 91-92, 2010.02. |
| 283. |
T. Nomura, Y. Korenaga, H. Matsuzaki, K. Koga, M. Shiratani, Y. Setsuhara, M. Sekine, M. Hori, Control of deposition profile of hard carbon films on trenched substrates using H-assisted plasma CVD reactor, Proc. of the 27th symposium on plasma processing, P1-39, 205-206, 2010.02. |
| 284. |
Substrate Temperature Dependence of Sticking Probability of SiOx-CH3 Nano-Particles. |
| 285. |
Optical and Electrical Properties of Particle Composite Thin Films deposited in SiH4/H2 and N2 Multi-Hollow Discharges. |
| 286. |
Generation of nitridated silicon particles and their thin film deposition using double multi-hollow discharges. |
| 287. |
Carbon dust particles generated due to H2 plasma-carbon wall interaction. |
| 288. |
Shojiro Komatsu, Yuhei Sato, Daisuke Hirano, Takuya Nakamura, Kazunori Koga, Atsushi Yamamoto, Takahiro Nagata, Toyohiro Chikyo, Takayuki Watanabe, Takeo Takizawa, Katsumitsu Nakamura, Takuya Hashimoto, Masaharu Shiratani, P-type sp(3)-bonded BN/n-type Si heterodiode solar cell fabricated by laser-plasma synchronous CVD method, JOURNAL OF PHYSICS D-APPLIED PHYSICS, 10.1088/0022-3727/42/22/225107, 42, 22, 2009.11, A heterojunction of p-type sp(3)-bonded boron nitride (BN) and n-type Si fabricated by laser-plasma synchronous chemical vapour deposition (CVD) showed excellent rectifying properties and proved to work as a solar cell with photovoltaic conversion efficiency of 1.76%. The BN film was deposited on an n-type Si (1 0 0) substrate by plasma CVD from B2H6 + NH3 + Ar while doping of Si into the BN film was induced by the simultaneous irradiation of an intense excimer laser with a pulse power of 490 mJ cm(-2), at a wavelength of 193 nm and at a repetition rate of 20 Hz. The source of dopant Si was supposed to be the Si substrate ablated at the initial stage of the film growth. The laser enhanced the doping (and/or diffusion) of Si into BN as well as the growth of sp(3)-bonded BN simultaneously in this method. P-type conduction of BN films was determined by the hot (thermoelectric) probe method. The BN/Si heterodiode with an essentially transparent p-type BN as a front layer is supposed to efficiently absorb light reaching the active region so as to potentially result in high efficiency.. |
| 289. |
J. Umetsu, K. Inoue, T. Nomura, H. Matsuzaki, K. Koga, M. Shiratani, Y. Setsuhara, M. Sekine, M. Hori, Substrate temperature dependence of deposition profile of plasma CVD carbon films in trenches, J. Plasma Fusion Res., 8, 1443-1446, 2009.09. |
| 290. |
W. M. Nakamura, Y. Kawashima, M. Tanaka, H. Sato, J. Umetsu, H. Miyahara, H. Matsuzaki, K. Koga, M. Shiratani, Optical Emission Spectroscopy of a Magnetically Enhanced Multi-hollow Discharge Plasma for a-Si:H Deposition, J. Plasma Fusion Res., 8, 736-739, 2009.09. |
| 291. |
H. Miyahara, S. Iwashita, H. Miyata, H. Matsuzaki, K. Koga, M. Shiratani, Detection of nano-particles formed in cvd plasma using a two-dimensional photon-counting laser-light-scattering method, J. Plasma Fusion Res., 8, 700-704, 2009.09. |
| 292. |
H. Sato, Y. Kawashima, M. Tanaka, K. Koga, W. M. Nakamura, M. Shiratani, Dependence of volume fraction of clusters on deposition rate of a-Si:H films deposited using a multi-hollow discharge plasma CVD method, J. Plasma Fusion Res., 8, 1435-1438, 2009.09. |
| 293. |
S. Iwashita, H. Miyata, H. Matsuzaki, K. Koga, M. Shiratani, Control of Three Dimensional Transport of Nano-blocks by Amplitude Modulated Pulse RF Discharges using an Electrode with Needles, J. Plasma Fusion Res., 8, 582-586, 2009.09. |
| 294. |
S. Iwashita, H. Miyata, K. Koga, M. Shiratani, N. Ashikawa, K. Nishimura, A. Sagara, the LHD experimental group, A comparison of dust particles produced due to interaction between graphite and plasma: LHD vs helicon discharges, J. Plasma Fusion Res., 8, 308-311, 2009.09. |
| 295. |
M. Shiratani, K. Koga, Toward plasma nano-factories, Proc. of 2nd International Conference on Advanced Plasma Technologies (iCAPT-II) with 1st International Plasma Nanoscience Symposium (iPlasmaNano-I), 86, 2009.09. |
| 296. |
Y. Kawashima, H. Sato, K. Koga, M. Shiratani, M. Kondo, Synthesis of Si nanoparticles for multiple exciton generation solar cells using multi-hollow discharge plasma CVD, Proc. of 2009 International Symposium on Dry Process, 107, 2009.09. |
| 297. |
T. Nomura, Y. Korenaga, J. Umetsu, H. Matsuzaki, K. Koga, M. Shiratani, Y. Setsuhara, M. Sekine, M. Hori, Pressure, aspect ratio dependence of deposition profile of carbon films on trench substrates deposited by plasma CVD, Proc. of 2009 International Symposium on Dry Process, 101, 2009.09. |
| 298. |
S. Iwashita, H. Miyata, K. Koga, H. Matsuzaki, M. Shiratani, M. Akiyama, Porosity Control of Nano-Particle Composite Porous Low Dielectric Films using Pulse RF Discharges with Amplitude Modulation, Proc. of 2009 International Symposium on Dry Process, 99, 2009.09. |
| 299. |
H. Sato, Y. Kawashima, K. Koga, M. Shiratani, Measurements of Surface Temperature of a-Si:H Films in Silane Multi-Hollow Discharge with IR Thermometer, Proc. of 2009 International Symposium on Dry Process, 113, 2009.09. |
| 300. |
K. Nakahara, Y. Kawashima, H. Sato, K. Koga, M. Shiratani, Measurements of electron density in SiH4+H2 multi-hollow discharges using a frequency shift probe, Proc. of 2009 International Symposium on Dry Process, 163, 2009.09. |
| 301. |
H. Miyata, S. Iwashita, YasuY. Yamada, K. Koga, M. Shiratani, Dust Particles formed owing to interactions between H2 or D2 helicon plasma, graphite, Proc. of 2009 International Symposium on Dry Process, 33, 2009.09. |
| 302. |
M. Shiratani, S. Iwashita, H. Miyata, K. Koga, H. Matsuzaki, M. Akiyama, Plasma CVD of Nano-particle Composite Porous SiOCH Films, Proc. of 19th International Symposium on Plasma Chemistry, 2009.07. |
| 303. |
KOGA Kazunori, IWASHITA Shinya, KIRIDOSHI Satoru, SHIRATANI Masaharu, ASHIKAWA Naoko, NISHIMURA Kiyohiko, SAGARA Akio, KOMORI Akio, LHD Experimental Group, Characterization of Dust Particles Ranging in Size from 1 nm to 10 µm Collected in the LHD, Plasma and Fusion Research, 10.1585/pfr.4.034, 4, 34-34, 2009.04, We collected dust particles ranging in size from 1 nm to 10 µm from the Large Helical Device employing two methods: an ex-situ filtered vacuum collection method and an in-situ dust collection method. The size distribution from 1 nm to 10 µm is well expressed by the Junge distribution. Dust particles are classified into three kinds: small spherical dust particles below 1 µm in size, agglomerates consisting of primary particles of 10 nm, and large dust particles above 1 µm in size and irregular in shape; this suggests three formation mechanisms of dust particles: chemical vapor deposition growth, agglomeration, and peeling from walls. In-situ collection shows that agglomeration between dust particles takes place in main discharges. The primary dust particles in agglomerates are around 10 nm in size, suggesting agglomeration between a negatively charged large agglomerate and a positively charged dust particle 10 nm in size. We have also confirmed the important fact that a large number of dust particles move during vacuum vent. Therefore, the in-situ dust collection method is needed to reveal the generation-time and -processes of dust particles and their deposition position during discharges.. |
| 304. |
S. Iwashita, H. Miyata, H. Matsuzaki, K. Koga, M. Shiratani, Nano-block manipulation using pulse RF discharges with amplitude modulation combined with a needle electrode, Proc. of PSS2009/SPP26, 2009.02. |
| 305. |
K. Koga, W. M. Nakamura, H. Sato, M. Tanaka, H. Miyahara, M. Shiratani, High Rate Deposition of a-Si:H Depositied using a Low Gas Pressure Multi-hollow Discharge Plasma CVD Method, Proc. of PSS2009/SPP26, 2009.02. |
| 306. |
Nakamura W. M., Sato H., Koga K., Shiratani M., Effects of magnetic fields on multi-hollow discharges for thin film silicon solar cells, Proc. of PSS2009/SPP26, 2009.02. |
| 307. |
J. Umetsu, K. Inoue, T. Nomura, H. Matsuzaki, K. Koga, M. Shiratani, Y. Setsuhara, M. Sekine, M. Hori, Deposition profile of toluene plasma CVD carbon films in trenches, Proc. of PSS2009/SPP26, 2009.02. |
| 308. |
K. Koga, Y. Kawashima, W. M. Nakamura, H. Sato, M. Tanaka, M. Shiratani, M. Kondo, Conductivity of nc-Si films depsited using multi-hollow discharge plasma CVD method, Proc. of PSS2009/SPP26, 2009.02. |
| 309. |
S. Iwashita, H. Miyata, K. Koga, M. Shiratani, N. Ashikawa, A. Sagara, K. Nisimura, Characteristics of dust particles produced due to interaction between hydrogen plasma, graphite, Proc. of PSS2009/SPP26, 2009.02. |
| 310. |
S. Iwashita, H. Miyata, K. Koga, H. Matsuzaki, M. Shiratani, M. Akiyama, Plasma CVD of Nano-particle Composite Porous Films of k=1.4-2.9, Young’s Modulus above 10 GPa, Proc. of 30th International Symposium on Dry Process, 115, 2008.12. |
| 311. |
J. Umetsu, K. Inoue, T. Nomura, H. Matsuzaki, K. Koga, Y. Setsuhara, M. Shiratani, M. Sekine, M. Hori, Deposition profile of plasma CVD carbon films in trenches, Proc. of 30th International Symposium on Dry Process, 35, 2008.12. |
| 312. |
William Makoto Nakamura, Hiroomi Miyahara, Hiroshi Sato, Hidefumi Matsuzaki, Kazunori Koga, Masaharu Shiratani, Two-dimensional spatial profile of volume fraction of nanoparticles incorporated into a-Si : H films deposited by plasma CVD, IEEE TRANSACTIONS ON PLASMA SCIENCE, 10.1109/TPS.2008.923830, 36, 4, 888-889, 2008.08, Using an optical-scanning method, we obtained 2-D spatial profile of deposition rate of hydrogenated amorphous silicon (a-Si:H) films deposited by a multihollow discharge plasma CVD with a high spatial resolution. From the profile, we deduced 2-D spatial profile of the volume fraction of nanoparticles incorporated into films, since nanoparticles affect optical and electronic properties of a-Si:H films.. |
| 313. |
Shinya Iwashita, Michihito Morita, Hidefumi Matsuzaki, Kazunori Koga, Masaharu Shiratani, Temperature Dependence of Dielectric Constant of Nanoparticle Composite Porous Low-k Films Fabricated by Pulse Radio Frequency Discharge with Amplitude Modulation, JAPANESE JOURNAL OF APPLIED PHYSICS, 10.1143/JJAP.47.6875, 47, 8, 6875-6878, 2008.08, Nanoparticle composite porous low-k films are deposited by pulse radio frequency (RF) discharge with the amplitude modulation (AM) of discharge voltage. The deposition rate obtained with AM is 0.65 nm/s, which is sevenfold as high as that obtained without AM. and porosity = 60-63% and dielectric constant k = 1.1-1.4 for the films obtained with AM are nearly equal to those obtained without AM. The deposition of porous low-k films by pulse RF discharge with AM is a promising method for increasing the deposition rate with a less pronounced agglomeration and without variations in the properties of the films. With decreasing substrate temperature from 403 to 368 K, the porosity of the films increases from 3.5 to 60%, leading to a reduction in their dielectric constant from 2.9 to 1.4. Substrate temperature is a key parameter that determines the porosity and dielectric constant of the porous low-k films.. |
| 314. |
S. Iwashita, K. Koga, M. Morita, M. Shiratani, Rapid transport of nano-particles in amplitude modulated rf discharges for depositing porous ultra-low-k films, J. Phys. : Conference Series, 10.1088/1742-6596/100/6/062006, 100, 6, p. 062006, 2008.08. |
| 315. |
J. Umetsu, K. Koga, K. Inoue, M. Shiratani, Optical emission spectroscopic study on H-assisted plasma for anisotropic deposition of Cu films, J. Phys. : Conference Series, 10.1088/1742-6596/100/6/062007, 100, 6, p. 062007, 2008.08. |
| 316. |
Shota Nunomura, Masaharu Shiratani, Kazunori Koga, Michio Kondo, Yukio Watanabe, Nanoparticle coagulation in fractionally charged and charge fluctuating dusty plasmas, PHYSICS OF PLASMAS, 10.1063/1.2972162, 15, 8, p. 080703, 2008.08, The kinetics of nanoparticle coagulation has been studied in fractionally charged and charge fluctuating dusty plasmas. The coagulation occurs when the mutual collision frequency among nanoparticles exceeds their charging and decharging/neutralization frequency. Interestingly, the coagulation is suppressed while a fraction (several percent) of nanoparticles are negatively charged in a plasma, in which stochastic charging plays an important role. A model is developed to predict a phase diagram of the coagulation and its suppression. (C) 2008 American Institute of Physics.. |
| 317. |
Jun Umetsu, Kazunori Koga, Kazuhiko Inoue, Hidefumi Matsuzaki, Kosuke Takenaka, Masaharu Shiratani, Discharge power dependence of Hαintensity and electron density of Ar + H2discharges in H-assisted plasma CVD reactor, Surface and Coatings Technology, 10.1016/j.surfcoat.2008.06.108, 202, 22-23, 5659-5662, 2008.08, We have realized anisotropic deposition of Cu, for which Cu is preferentially filled from the bottom of trenches without being deposited on the sidewall of trenches, using H-assisted plasma CVD. To obtain information about a discharge condition to realize a high deposition rate, we have studied dependence of Hα656.3 nm and Ar 811.5 nm intensities and electron density in the main discharge on the main discharge power, Pm, and in the discharge of H atom source on the discharge power of H atom source, PH, as a parameter of a gas flow rate ratio R = H2/(H2+ Ar). The results suggest that a high electron density in the main discharge and high fluxes of ions and H atoms to a substrate, all of which are needed for deposition of high purity Cu at a high deposition rate, are realized for Pm= 45 W, PH= 500 W, and R = 3.3%. © 2008 Elsevier B.V. All rights reserved.. |
| 318. |
W. M. Nakamura, K. Koga, H. Miyahara, M. Shiratani, Cluster incorporation control for a-Si:H film deposition, J. Phys. : Conference Series, 10.1088/1742-6596/100/8/082018, 100, 8, p. 082018, 2008.08. |
| 319. |
M. Shiratani, W. M. Nakamura, H. Miyahara, K. Koga, Nanoparticle-Suppressed Plasma CVD for Depositing Stable a-Si:H Films, Digest of Technical Papers of the Fifteenth International Workshop on Active-Matrix Flatpanel Displays, Devices (AM-FPD 08), 69, 2008.07. |
| 320. |
Yukio Watanabe, Masaharu Shiratani, Kazunori Koga, Growth Control of Clusters in Reactive Plasmas and Application to High-Stability a-Si: H Film Deposition, Advanced Plasma Technology, 10.1002/9783527622184.ch12, 227-242, 2008.04. |
| 321. |
M. Shiratani, S. Iwashita, K. Koga, S. Nunomura, Rapid transport of nano-particles having a fractional elemental charge on average in capacitively coupled rf discharges by amplitude modulating discharge voltage, Faraday Discussions, 10.1039/B704910B , 137, 127-138, 2008.01. |
| 322. |
K. Koga, W. M. Nakamura, and M. Shiratani, VHF discharge sustained in a small hole, Proc. 28th Intern. Conf. on Phenomena in Ionized Gases, 1987-1989, 2007.07. |
| 323. |
Kazunori Koga, Shinya Iwashita, Masaharu Shiratani, Transport of nano-particles in capacitively coupled rf discharges without and with amplitude modulation of discharge voltage, JOURNAL OF PHYSICS D-APPLIED PHYSICS, 10.1088/0022-3727/40/8/S05, 40, 8, 2267-2271, 2007.04, Transport of nano-particles in rf discharges without and with an amplitude modulation (AM) of the discharge voltage has been examined using a two-dimensional laser-light-scattering method. During the discharging period, nano-particles are mainly generated in the plasma/sheath boundary region near the powered electrode. They move away from their generation region towards the upper grounded electrode after turning off discharges due to thermophoretic force. Using AM discharges, nano-particles can be transported, during the modulation period, from their generation region to the plasma/sheath boundary region near the upper grounded electrode. The transport time is at least six times shorter than that after turning off unmodulated discharges. Two key parameters for the fast transport using AM discharges are the discharge voltage and the period of the AM.. |
| 324. |
Masaharu Shiratani, Kazunori Koga, Soichiro Ando, Toshihisa Inoue, Yukio Watanabe, Shota Nunomura, Michio Kondo, Single step method to deposit Si quantum dot films using H-2+SiH4VHF discharges and electron mobility in a Si quantum dot solar cell, SURFACE & COATINGS TECHNOLOGY, 10.1016/j.surfcoat.2006.07.012, 201, 9-11, 5468-5471, 2007.02, To fabricate quantum dot solar cells of a high efficiency at a low cost, here we propose a Si quantum dot film which is composed of Si nanocrystallites embedded into a-Si:H and a single step method to deposit such Si quantum dot films using H-2 + SiH4 VHF discharges. For the method, Si nano-crystallites of a small size dispersion and radicals produced in the discharges are co-deposited on a substrate to form Si quantum dot films. Using the method, we realized a volume fraction of dots in films of 0.3-70%. Photo- and dark-conductivity of films are in a range of 10(-11)-10(-9) and 10(-5)-10(-4) S/cm, respectively. We have examined effects of the size dispersion of nano-crystallites on electron mobility in a quantum dot Si solar cell by a simulation. The electron mobility in films for a size dispersion of 0.37 nm is about 50% of that in films for no size dispersion. (C) 2006 Elsevier B.V. All rights reserved.. |
| 325. |
Shinya Iwashita, Kazunori Koga, Masaharu Shiratani, A device for trapping nano-particles formed in processing plasmas for reduction of nano-waste, SURFACE & COATINGS TECHNOLOGY, 10.1016/j.surfcoat.2006.07.060, 201, 9-11, 5701-5704, 2007.02, Removal of nano-particles is important from the viewpoint that nano-materials may be hazardous to health when they deposit within the respiratory system. We have developed a method for measuring a sticking probability of nano-particles to a wall. The probability of nano-particles above 2 mn in size to a stainless-steel wall is close to 100% at a low ambient pressure below about 160 Pa. Based on this result, we have developed a device for trapping nano-particles formed in low pressure processing plasmas in order to reduce nano-waste, that is, waste of mit in size. The device traps nano-particles by collision and attachment of nano-particles to its surface. The trapping efficiency of the device for nanoparticles above 2 mr, in size is more than 99.8% at a low ambient pressure below about 160 Pa. (C) 2006 Elsevier B.V. All rights reserved.. |
| 326. |
S. Iwashita, K. Koga, M. Shiratani, Transport of nano-particles in pulsed AM RF discharges, Proc. the 24th Symp. on Plasma Processing, 103-104, 2007.01. |
| 327. |
K. Koga, W. M. Nakamura, D. Shimokawa, M. Shiratani, Stability of a-Si:H deposited using multi-hollow plasma CVD, Proc. the 24th Symp. on Plasma Processing, 189-190, 2007.01. |
| 328. |
M. Shiratani, S. Kiridoshi, K. Koga, S. Iwashita, N. Ashikawa, K. NIshimura, A. Sagara, A. Komori, LHD Experimental Group, In-situ sampling of dust generated in LHD and its analysis, Proc. the 24th Symp. on Plasma Processing, 371-372, 2007.01. |
| 329. |
M Shiratani, K Koga, N Kaguchi, K Bando, Y Watanabe, Species responsible for Si-H-2 bond formation in a-Si : H films deposited using silane high frequency discharges, THIN SOLID FILMS, 10.1016/j.tsf.2005.08.015, 506, 17-21, 2006.05, Species responsible for Si-H-2 bond formation in a-Si:H films have been studied by using a cluster-suppressed plasma CVD reactor of a diode configuration. The concentration of Si-H-2 bonds in a-Si:H films linearly decreases with decreasing the volume fraction V-f of clusters incorporated into the films, while the density of higher-order silane such as Si2H5 and Si3H7 correlates little with the bond concentration. The experimental results obtained using the diode configuration motivate us to employ a reactor of triode configuration in order to reduce the V-f value. The a-Si:H Schottky solar cell prepared with this configuration has the high initial fill factor FF=0.60 and high stabilized value after light soaking FF=0.56. (c) 2005 Elsevier B.V. All rights reserved.. |
| 330. |
T Kakeya, K Koga, M Shiratani, Y Watanabe, M Kondo, Production of crystalline Si nano-clusters using pulsed H-2+SiH(4)VHFdischarges, THIN SOLID FILMS, 10.1016/j.tsf.2005.08.090, 506, 288-291, 2006.05, Crystalline Si nano-clusters are successfully produced using pulsed H-2+SiH4 VHF discharges. Their size can be controlled by changing the discharge duration. Si clusters of 1.6 nm in size and 100% crystallinity are produced. Collecting efficiency of them on the substrate decreases by one order of magnitude by heating it from room temperature to 200 degrees C, while their size is around 3 nm irrelevant to its temperature change. (c) 2005 Elsevier B.V. All rights reserved.. |
| 331. |
K Koga, Y Kitaura, M Shiratani, Y Watanabe, A Komori, Nano-particle formation due to interaction between H-2 plasma and carbon wall, THIN SOLID FILMS, 10.1016/j.tsf.2005.08.062, 506, 656-659, 2006.05, Formation of carbon particles due to interaction between plasma and carbon fiber composite (CFC) or graphite targets has been studied using an electron cyclotron resonance (ECR) plasma device. The interaction produces two kinds of particles: small ones have a size of 2-25 nm, spherical shape; large ones have a size above 100 nm, irregular shape. Total amount and average size of small particles tend to decrease with increasing sheath voltage V-s between plasma and the carbon targets from 14 V to 214 V. Optical emission intensities of C and CH decrease with increasing V-s, while gas absorption rate to the target increases. These results suggest that carbon-containing species emitted from the carbon targets contribute to formation of small particles. (c) 2005 Elsevier B.V. All rights reserved.. |
| 332. |
K Takenaka, K Koga, M Shiratani, Y Watanabe, T Shingen, Mechanism of Cu deposition from Cu(EDMDD)(2) using H-assisted plasma CVD, THIN SOLID FILMS, 10.1016/j.tsf.2005.08.028, 506, 197-201, 2006.05, Mechanism of high purity Cu thin film deposition from a new F-free Cu complex, Cu(EDMDD)(2) have been studied using H-assisted plasma CVD (HAPCVD). The species of Cu(EDMDD) is the dominant neutral radical dissociated from Cu(EDMDD)2 by electron impact. In situ measurements by Fourier transform infrared (FTIR) spectroscopy show that H atoms are quite effective in removing impurities in Cu films. The simplified version of important surface reaction is Cu(EDMDD)+H -> Cu+H(EDMDD). Cu films deposited by HAPCVD have a low as-deposited resistivity of 1.84 mu Omega cm and is 20 nm thick in trenches 0.5 mu m wide and 2.73 mu m deep. (c) 2005 Elsevier B.V. All rights reserved.. |
| 333. |
S Nunomura, M Kita, K Koga, M Shiratani, Y Watanabe, In situ simple method for measuring size and density of nanoparticles in reactive plasmas, JOURNAL OF APPLIED PHYSICS, 10.1063/1.2189951, 99, 8, 083302(7pages), 2006.04, A laser-light-scattering (LLS) method for measuring the size and density of nanoparticles generated in reactive plasmas has been developed. The size and density of the nanoparticles are determined from their thermal coagulation that takes place after turning off the discharge. The measurable size and density range of the LLS method is n(p)10(13) (m(-3/2))xd(p)(-5/2)L(-2)n(g)(-1), where n(p), d(p), L, and n(g) are the density, size, and diffusion length of the nanoparticles, and the density of a background gas, respectively. The method has been demonstrated by measurement of the size and density of nanoparticles formed by the radio-frequency discharge of dimethyldimethoxysilane Si(CH3)(2)(OCH3)(2) diluted with Ar. Using a simple optical setup for the LLS measurement, nanoparticles are detected down to approximate to 1 nm in size when they are generated at a density of approximate to 10(12) cm(-3). The developed method is widely applicable to other systems in which thermal coagulation takes place. (C) 2006 American Institute of Physics.. |
| 334. |
Masaharu Shiratani, Takao Kaji, Kazunori Koga, Yukio Watanabe, Tomohiro Kubota, Seiji Samukawa, Plasma anisotropic CVD of high purity Cu using Cu(hfac)2, 6th International Conference on Reactive Plasmas and 23rd Symposium on Plasma Processing, 2006.01. |
| 335. |
S. Nunomura, K. Koga, M. Shiratani, Y. Watanabe, Y. Morisada, N. Matsuki, and S. Ikeda, Fabrication of nanoparticle composite porous films having ultra-low dielectric constant, Jpn. J. Appl. Phys., 10.1143/JJAP.44.L1509, 44, 50, L1509-L1511, 2005.12. |
| 336. |
K. Koga, T. Inoue, K. Bando, S. Iwashita, M. Shiratani, and Y. Watanabe, Highly stable a-Si:H films deposited by using multi-hollow plasma chemical vapor deposition, Jpn. J. Appl. Phys., 10.1143/JJAP.44.L1430, 44, 48, L1430-L1432, 2005.11. |
| 337. |
K Koga, N Kaguchi, K Bando, M Shiratani, Y Watanabe, Cluster-eliminating filter for depositing cluster-free a-Si : H films by plasma chemical vapor deposition, REVIEW OF SCIENTIFIC INSTRUMENTS, 10.1063/1.2126572, 76, 11, 1-4, 2005.11, A cluster-eliminating filter is developed to reduce a volume fraction V-F of amorphous silicon nanoparticles above approximately 1 nm in size (referred to as a cluster) incorporated into a-Si:H films. The filter reduces the V-F value by using the difference between a sticking probability of clusters and a surface reaction probability of SiH3 radicals, which are the predominant deposition radicals. By employing the filter together with a cluster-suppressed plasma chemical vapor deposition reactor, the V-F value is reduced below 1/180 compared to that for the conventional device quality films. Such cluster-free a-Si:H films have an extremely small hydrogen concentration associated with Si-H-2 bonds below 5.46x10(-3) at. %. (c) 2005 American Institute of Physics.. |
| 338. |
M. Shiratani, T. Kakeya, K. Koga, Y. Watanabe, and M. Kondo, Production of crystalline Si nano-particles using VHF discharges and their properties, Trans. Mateｒ. Res. Soc. Jpn., 30, 1, 307-310, 2005.03. |
| 339. |
Y. Watanabe, M. Shiratani, K. Koga, Preparation of high-quality a-Si:H using cluster-suppressed plasma CVD method and its prospects, Trans. Mateｒ. Res. Soc. Jpn., 30, 1, 267-272, 2005.03. |
| 340. |
K Takenaka, M Shiratani, M Takeshita, M Kita, K Koga, Y Watanabe, Control of deposition profile of copper for large-scale integration (LSI) interconnects by plasma chemical vapor deposition, PURE AND APPLIED CHEMISTRY, 10.1351/pac200577020391, 77, 2, 391-398, 2005.02, H-assisted plasma chemical vapor deposition (HAPCVD) realizes control of deposition profile of Cu in trenches. The key to the control is ion irradiation to surfaces. With increasing the flux and energy of ions, the profile changes from conformal to subconformal and then to an anisotropic one, for which Cu material is filled from the bottom of the trench without deposition on the sidewall. H-3(+) and ArH+ are identified as the major ionic species which contribute to the control, and hence the deposition profile also depends on a ratio R = H-2/(Ar + H-2).. |
| 341. |
K Koga, N Kaguchi, M Shiratani, Y Watanabe, Correlation between volume fraction of clusters incorporated into a-Si : H films and hydrogen content associated with Si-H-2 bonds in the films, JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A, 10.1116/1.1763905, 22, 4, 1536-1539, 2004.07, A downstream-cluster-collection method of high sensitivity has been developed to obtain information on size distribution, density, shape, and structure of clusters formed in reactive plasmas. The method have been applied together with a cluster-suppressed plasma chemical vapor deposition method in order to study a correlation between a volume fraction V-f of clusters incorporated into a-Si:H films and a hydrogen content C-H(SiH2) associated with Si-H-2 bonds in the films. The C-H(SiH2) value decreases almost linearly from 0.6 at. % to 0.05 at. % with decreasing V-f by about one order of magnitude. The result indicates that the incorporation of clusters, above about 1 nm in size, of amorphous structure into a-Si:H films is an important origin of Si-H-2 bonds in the films. (C) 2004 American Vacuum Society.. |
| 342. |
K Takenaka, M Kita, T Kinoshita, K Koga, M Shiratani, Y Watanabe, Anisotropic deposition of Cu in trenches by H-assisted plasma chemical vapor deposition, JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A, 10.1116/1.1738663, 22, 4, 1903-1907, 2004.07, We have realized anisotropic deposition of Cu, for which Cu is filled preferentially from the bottom of trenches without being deposited on their sidewall, using H-assisted plasma chemical vapor deposition. The anisotropic deposition has two interesting features. One is the fact that the narrower the width of trench, the faster the deposition rate on its bottom becomes. The other is the self-limiting characteristic, that is the deposition in the trench stops automatically just after filling it completely. Such a type of deposition has a potential to overcome common problems associated with conformal filling: namely, small crystal grain size below half of the trench width, and formation of a seam with residual impurities of relatively high concentration. (C) 2004 American Vacuum Society.. |
| 343. |
K Koga, R Uehara, Y Kitaura, M Shiratani, Y Watanabe, A Komori, Carbon particle formation due to interaction between H-2 plasma and carbon fiber composite wall, IEEE TRANSACTIONS ON PLASMA SCIENCE, 10.1109/TPS.2004.828129, 32, 2, 405-409, 2004.04, Formation of carbon particles due to plasma surface interaction has been studied using an electron cyclotron resonance (ECR) plasma device. The interaction produces two sizes of groups: small spherical ones of 2-25 nm in size and large particles of irregular shape and above 100 nm in size. The latter are considered to be flakes peeled from carbon films deposited on the reactor wall. The total amount and average size of small particles tends to decrease with increasing the sheath voltage V. between plasma and the carbon fiber composite (CFC) wall from 14 to 214 V. Optical emission intensities of CH and C as well as gas absorption rate to the CFC wall also decrease with increasing V-S. These results suggest that the carbon-containing species emitted from the CFC wall contribute to formation of small particles.. |
| 344. |
K. Koga, R. Uehara, Y. Kitaura, M. Shiratani, Y. Watanabe, A. Komori, Carbon particle formation due to interaction between H2 plasma and carbon fiber composite wall, IEEE Trans. Plasma Science, 10.1109/TPS.2004.828129 , 32, 2, 405-409, 2004.02. |
| 345. |
M. Shiratani, K. Koga, A. Harikai, T. Ogata, and Y. Watanabe, Effects of Excitation Frequency and H2 Dilution on Cluster Generation in Silane High-Frequency Discharges, MRS Symp. Proc., 10.1557/PROC-762-A9.5, 762, A9.5.1-9.5.6, 2003.04. |
| 346. |
K. Takenaka, M. Onishi, M. Takeshita, T. Kinoshita, K. Koga, M. Shiratani, and Y. Watanabe, Anisotropic Plasma Chemical Vapor Deposition of Copper Films in Trenches, MRS Symp. Proc., 10.1557/PROC-766-E3.8, 766, E3.8.1-3.8.6, 2003.04. |
| 347. |
Growth of Clusters in Silane Plasma and Their Relation to Deposition of Thin Films. |
| 348. |
M Shiratani, K Koga, Y Watanabe, Cluster-suppressed plasma CVD for deposition of high quality a-Si : H films, THIN SOLID FILMS, 10.1016/S0040-6090(02)01171-9, 427, 1-2, 1-5, 2003.03, Correlation between microstructure parameter of a-Si:H films and cluster amount in silane discharges is revealed by using a cluster-suppressed plasma CVD method. The microstructure parameter R-alpha of a-Si:H films decreases below 0.003 with decreasing the cluster amount. A Schottky solar cell of a-Si:H films of Ralpha = 0.057 shows a high initial fill factor (FF) of 0.57 and high stabilized FF of 0.53. In addition, amount of clusters incorporated into a-Si:H films prepared for a discharge frequency f = 60 MHz is significantly low compared to those for f = 13.56, 40 MHz. These results suggest that the deposition of high quality a-Si:H films at a high rate can be realized by the cluster-suppressed plasma CVD method together with very high frequency discharges. (C) 2002 Elsevier Science B.V. All rights reserved.. |
| 349. |
K. Takenaka, M. Shiratani, M. Onishi, M. Takeshita, T. Kinoshita, K. Koga, and Y. Watanabe, Anisotropic Deposition of Copper by H-Assisted Plasma Chemical Vapor Deposition, Matr. Sci. Semiconductor Processing, 10.1016/S1369-8001(02)00108-7, 5, 2, 301-304, 2003.02. |
| 350. |
M. Shiratani, K. Koga, Y. Watanabe, Formation of nano-particles in microgravity plasma, Journal of Japan Society of Microgravity Application, 19, 69, 2002.10. |
| 351. |
K. Takenaka, M. Onishi, M. Takenaka, T. Kinoshita, K. Koga, M. Shiratani, Y. Watanabe, Anisotropic deposition of copper by plasma CVD method, Proc. Intern. Symp. on Dry Process, 221-226, 2002.10. |
| 352. |
Y. Watanabe, M. Shiratani, K. Koga, Nucleation and subsequent growth of clusters in reactive plasma (invited lecture paper), Plasma Sources Sci. Technol., 10.1088/0963-0252/11/3A/334, 11, A229-A233, 2002.08. |
| 353. |
M. Shiratani, M. Kai, K. Imabeppu, K. Koga, Y. Watanabe, Correlation between Si cluster amount in silane HF discharges and quality of a-Si:H films, Proc. ESCANPIG16/ICRP5 Joint Meeting, II323--II324, 2002.07. |
| 354. |
K. Takenaka, H. J. Jin, M. Onishi, K. Koga, M. Shiratani, Y. Watanabe, T. Shingen, Conformal deposition of pure Cu films in trenches by H-assisted plasma CVD using Cu(EDMDD)2, Proc. ESCANPIG16/ICRP5 Joint Meeting, II173--II174, 2002.07. |
| 355. |
K. Takenaka, H. J. Jin, M. Onishi, K. Koga, M. Shiratani, Y. Watanabe, Anisotropic deposition of Cu with H-assisted plasma CVD, Proc. ESCANPIG16/ICRP5 Joint Meeting, II199--II200, 2002.07. |
| 356. |
K. Koga, K. Imabeppu, M. Kai, A. Harikai, M. Shiratani, Y. Watanabe, Suppression methods of cluster growth in silane discharges and their application to deposition of super high quality a-Si:H films, Proc. Intern. Workshop on Information and Electrical Engineering (IWIE2002), 238-243, 2002.05. |
| 357. |
K. Takenaka, M. Onishi, T. Kinoshita, K. Koga, M. Shiratani, Y. Watanabe, T. Shingen, Deposition of Cu films in trenches for LIS interconnects by H-assisted plasma CVD method, Proc. Intern. Workshop on Information and Electrical Engineering (IWIE2002), 227-232, 2002.05. |
| 358. |
Y. Watanabe, A. Harikai, K. Koga, M. Shiratani, Clustering phenomena in low-pressure reactive plasma: basis and applications (invited lecture paper), Pure Appl. Chem. , 10.1351/pac200274030483, 74, 3, 483-487, 2002.03. |
| 359. |
Kazunori Koga, Motohide Kai, Masaharu Shiratani, Masaharu Shiratani, Yukio Watanabe, Nobuhiro Shikatani, Cluśter-suppressed plasma chemical vapor deposition method for high quality hydrogenated amorphous silicon films, Japanese Journal of Applied Physics, Part 2: Letters, 10.1143/JJAP.41.L168, 41, 2B, L168-L170, 2002.02, We have developed a novel plasma chemical vapor deposition (PCVD) method for preparing high quality hydrogenated amorphous silicon (a-Si:H) films, which suppresses effectively growth of clusters by transporting them out of the reactor using gas flow and thermophoresis. By utilizing this cluster-suppressed PCVD method, we have demonstrated deposition of quite high quality a-Si:H films, microstructure parameter Rαof which can be reduced below 0.003. The decrease in Rαvalue is closely related to the decrease in cluster amount. Preliminary evaluation of fill factor (FF) of the a-Si:H Schottky solar cell of the a-Si:H films of Rα= 0.057 shows the high initial value FFi= 0.57 and high stabilized value after-light-soaking FFa= 0.53.. |
| 360. |
K. Koga, M. Shiratani, Y. Watanabe, In-situ measurement of size and density of particles in sub-nm to nm size range, Proc. Nano-technology Workshop, 13-20, 2002.02. |
| 361. |
M. Shiratani, K. Koga, Y. Watanabe, Deposition of high-quality Si films by suppressing cluster growth in SiH4 high-frequency discharges, Proc. Nano-technology Workshop, 7-12, 2002.02. |
| 362. |
K. Takenaka, H. J. Jin, M. Onishi, K. Koga, M. Shiratani, Y. Watanabe, Deposition of pure copper thin films by H-assisted plasma CVD using a new Cu complex Cu(EDMDD)2, Proc. Intern. Symp. on Dry Process, 169-174, 2001.11. |
| 363. |
Masaharu Shiratani, Hong Jie Jin, Kosuke Takenaka, Kazunori Koga, Toshio Kinoshita, Yukio Watanabe, H-assisted plasma CVD of Cu films for interconnects in ultra-large-scale integration, SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS, 10.1016/S1468-6996(01)00131-0, 2, 3-4, 505-515, 2001.09, H-assisted plasma CVD (HAPCVD), in which Cu(hfac)(2) is supplied as the source material, realizes control of qualities of Cu films, since H irradiation is effective in purifying the Cu films, increasing the grain size, and reducing the surface roughness. Conformal deposition in fine trenches can be realized by decreasing dissociation degree of Cu(hfac)(2) using the HAPCVD. Cu(hfac) is identified as the radical mainly contributing to the deposition. Based on the results, we proposed a model in which Cu(hfac) and H react on surfaces to deposit Cu films. We also demonstrated conformal deposition of smooth Cu films of 30 nm thickness and 1.9 mu Omega cm resistivity and almost complete Cu filling in trenches 0.35 mu m wide and 1.6 mu m deep using the HAPCVD. (C) 2001 Elsevier Science Ltd. All rights reserved.. |
| 364. |
M. Shiratani, K. Koga, Y. Watanabe, Cluster-less plasma CVD reactor and its application to a-Si:H film deposition, Mat. Res. Soc. Symp. Proc., 10.1557/PROC-664-A5.6, A5.6.1-A5.6.6, 2001.07. |
| 365. |
Y. Watanabe, M. Shiratani, K. Koga, Nucleation and subsequent growth of clusters in reactive plasma (invited), Proc. Intern. Conf. on Phenomena in Ionized Gases, 15-16, 2001.07. |
| 366. |
M. Shiratani, H. J. Jin, K. Takenaka, K. Koga, T. Kinoshita, Y. Watanabe, Development of H-assisted plasma CVD reactor for Cu interconnects, Proc. Intern. Conf. on Phenomena in Ionized Gases, 147-148, 2001.07. |
| 367. |
K. Koga, T. Sonoda, N. Shikatani, M. Shiratani, Y. Watanabe, Deposition of super high quality a-Si:H thin films using cluster-suppressed plasma CVD reactor, Proc. Intern. Conf. on Phenomena in Ionized Gases, 39-40, 2001.07. |
| 368. |
Y. Watanabe, M. Shiratani, K. Koga, Clustering phenomena in low-pressure reactive plasma: base and applications (invited), Proc. Intern. Symp. on Plasma Chemistry, 726-730, 2001.07. |
| 369. |
M. Shiratani, A. Toyozawa, K. Koga, Y. Watanabe, Behavior of a particle injected in ion sheath of electropositive and electronegative gas discharges, Proc. Intern. Conf. on Phenomena in Ionized Gases, 153-154, 2001.07. |
| 370. |
Y. Watanabe, M. Shiratani, K. Koga, Formation kinetics and control of dust particles in capacitively-coupled reactive plasma (invited), Phys. Scripta, 10.1238/Physica.Topical.089a00029, T89, 29-32, 2001.01. |
| 371. |
M. Shiratani, K. Koga, Y. Watanabe, Plasma CVD method for Cu interconnects in ULSI (invited), Proc. of Plasma Science Symp. 2001/ 18th Symp. on Plasma Processing, 751-754, 2001.01. |
| 372. |
M. Shiratani, N. Shiraishi, K. Koga, Y. Watanabe, Measurements of surface reaction probability of SiH3, Proc. of Plasma Science Symp. 2001/ 18th Symp. on Plasma Processing, 419-420, 2001.01. |
| 373. |
M. Shiratani, H. J. Jin, K. Takenaka, K. Koga, T. Kinoshita, Y. Watanabe, H assisted control of quality and conformality in Cu film deposition using plasma CVD method, Proc. Advanced Metallization Conf. 2000, 271-278, 2001.01. |
| 374. |
K. Koga, K. Tanaka, M. Shiratani, Y. Watanabe, Effects of H2 dilution and excitation frequency on initial growth of clusters in silane plasma, Proc. Plasma Science Symp. 2001/ 18th Symp. on Plasma Processing, 385-386, 2001.01. |
| 375. |
M. Shiratani, T. Sonoda, N. Shikatani, K. Koga, Y. Watanabe, Development of cluster-suppressed plasma CVD reactor for high quality a-Si:H film deposition, Proc. of Plasma Science Symp. 2001/ 18th Symp. on Plasma Processing, 421-422, 2001.01. |
| 376. |
M. Shiratani, A. Toyozawa, K. Koga, Y. Watanabe, Behavior of a particle injected in ion sheath, Proc. of Plasma Science Symp. 2001/ 18th Symp. on Plasma Processing, 393-394, 2001.01. |
| 377. |
M. Shiratani, S. Maeda, Y. Matsuoka, K. Tanaka, K. Koga, Y. Watanabe, Methods of suppressing cluster growth in silane rf discharges, Mat. Res. Soc. Symp. Proc., 10.1557/PROC-609-A5.6, A5.6.1-A5.6.6, 2000.07. |
| 378. |
K Koga, Y Matsuoka, K Tanaka, M Shiratani, Y Watanabe, In situ observation of nucleation and subsequent growth of clusters in silane radio frequency discharges, APPLIED PHYSICS LETTERS, 10.1063/1.126922, 77, 2, 196-198, 2000.07, Growth processes of clusters in low-pressure and low-power silane radio frequency discharges are studied by using the newly developed double-pulse-discharge method which realizes in situ measurement of their size and density in a size range of 0.5-4 nm. The clusters begin to be composed of two size groups at about 10 ms after the discharge initiation: clusters in the small size group have an almost constant average size of about 0.5 nm through the discharge period, while those in the large one grow at about 4 nm/s in a monodisperse way. Time evolution of the measured average sizes and densities in the groups is transformed into that of size distributions assuming that the density of SinHx clusters for the small group decreases exponentially with the increase in the number of Si atoms, n, of them, and the size distribution for the large group is the lognormal one. The results show that a critical cluster size for nucleation is SinHx (n similar to 4). (C) 2000 American Institute of Physics. [S0003-6951(00)01828-3].. |
| 379. |
H. J. Jin, M. Shiratani, Y. Nakatake, K. Koga, T. Kinoshita, Y. Watanabe, Deposition of smooth thin Cu films in deep submicron trench by plasma CVD reactor with H atom source, Mat. Res. Soc. Symp. Proc., 10.1557/PROC-612-D9.2.1, D9.2.1-D9.2.6, 2000.07. |
| 380. |
R. Ichiki, M. Shindo, S. Yoshimura, K. Koga, Y. Kawai, Propagation characteristics of ion acoustic waves in an Ar/SF6 plasma, J. Phys. Soc. Jpn., 10.1143/JPSJ.69.1925, 69, 6, 1925-1926, 2000.06. |
| 381. |
H. J. Jin, M. Shiratani, Y. Nakatake, K. Koga, T. Kinoshita, Y. Watanabe, Filling subquater-micron trench structure with high-purity copper using plasma reactor with H atom source, Res. Rep. ISEE Kyushu Univ., 5, 1, 57-61, 2000.03. |
| 382. |
Y. Watanabe, M. Shiratani, T. Fukuzawa, K. Koga, Growth processes of particles up to nanometer size in high-frequency SiH4 plasma, Jour. Technical Phys., 41, 1, 505-519, 2000.01. |
| 383. |
M Shiratani, S Maeda, K Koga, Y Watanabe, Effects of gas temperature gradient, pulse discharge modulation, and hydrogen dilution on particle growth in silane RF discharges, JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS, 10.1143/JJAP.39.287, 39, 1, 287-293, 2000.01, The effects of gas temperature gradient, pulse discharge modulation, and hydrogen dilution on the growth of particles below about 10 nm in size in silane parallel-plate RF discharges are studied using a high-sensitivity photon-counting laser-lightscattering (PCLLS) method. Thermophoretic force due to the gas temperature gradient between the electrodes drives neutral particles above a few nm in size toward the cool RF electrode which is at room temperature. Pulse discharge modulation is much more effective in reducing the particle density when it is combined with the gas temperature gradient, and particles above a few nm in size cannot be detected by the PCLLS method even after 2 h. Hydrogen dilution of a high H-2/SiH4 concentration ratio above about 5 is also useful in suppressing particle growth in the radical production region around the plasma/sheath boundary near the RF electrode.. |
| 384. |
K. Koga, H. Naitou, Y. Kawai, Observation of Asymmetric Sheath Structure in Multi-Component Plasma Containing Negative Ions, J. Plasma Fusion Res., 2, 435-438, 1999.12. |
| 385. |
K. Koga, H. Naitou, Y. Kawai, Observation of Local Structures in Asymmetric Ion Sheath, J. Phys. Soc. Jpn., 10.1143/JPSJ.68.1578, 68, 5, 1578-1584, 1999.05. |
| 386. |
K. Koga, Y. Kawai, Behavior of the Ion Sheath Instability in a Negative Ion Plasma, Jpn. J. Appl. Phys., 10.1143/JJAP.38.1553, 38, 3A, 1553-1557, 1999.03. |
| 387. |
Observation of the Formation of Local Structures in the Asymmetric Ion Sheath. |
