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Takahashi, Masamitsu; Kozu, Miwa*; Sasaki, Takuo
Japanese Journal of Applied Physics, 55(4S), p.04EJ04_1 - 04EJ04_4, 2016/04
Times Cited Count:5 Percentile:23.64(Physics, Applied)Sasaki, Takuo; Ishikawa, Fumitaro*; Takahashi, Masamitsu
Applied Physics Letters, 108(1), p.012102_1 - 012102_5, 2016/01
Times Cited Count:4 Percentile:19.01(Physics, Applied)Shimomura, Kenichi*; Suzuki, Hidetoshi*; Sasaki, Takuo; Takahashi, Masamitsu; Oshita, Yoshio*; Kamiya, Itaru*
Journal of Applied Physics, 118(18), p.185303_1 - 185303_7, 2015/11
Times Cited Count:9 Percentile:36.75(Physics, Applied)Takahashi, Masamitsu; Kozu, Miwa*; Sasaki, Takuo; Hu, W.*
Crystal Growth & Design, 15(10), p.4979 - 4985, 2015/10
Times Cited Count:14 Percentile:70.13(Chemistry, Multidisciplinary)Sasaki, Takuo; Takahashi, Masamitsu
Nihon Kessho Seicho Gakkai-Shi, 42(3), p.210 - 217, 2015/10
Sasaki, Takuo; Takahashi, Masamitsu; Suzuki, Hidetoshi*; Oshita, Yoshio*; Yamaguchi, Masafumi*
Journal of Crystal Growth, 425, p.13 - 15, 2015/09
Times Cited Count:4 Percentile:35.32(Crystallography)Biermanns, A.*; Dimakis, E.*; Davydok, A.*; Sasaki, Takuo; Geelhaar, L.*; Takahashi, Masamitsu; Pietsch, U.*
Nano Letters, 14(12), p.6878 - 6883, 2014/12
Times Cited Count:27 Percentile:71.42(Chemistry, Multidisciplinary)Sasaki, Takuo; Norman, A. G.*; Romero, M. J.*; Al-Jassim, M. M.*; Takahashi, Masamitsu; Kojima, Nobuaki*; Oshita, Yoshio*; Yamaguchi, Masafumi*
Physica Status Solidi (C), 10(11), p.1640 - 1643, 2013/11
Times Cited Count:4 Percentile:82.88(Physics, Applied)Nishi, Toshiaki*; Sasaki, Takuo; Ikeda, Kazuma*; Suzuki, Hidetoshi*; Takahashi, Masamitsu; Shimomura, Kenichi*; Kojima, Nobuaki*; Oshita, Yoshio*; Yamaguchi, Masafumi*
AIP Conference Proceedings 1556, p.14 - 17, 2013/09
Times Cited Count:0 Percentile:0.00(Energy & Fuels)Hu, W.; Suzuki, Hidetoshi*; Sasaki, Takuo*; Kozu, Miwa*; Takahashi, Masamitsu
Journal of Applied Crystallography, 45(5), p.1046 - 1053, 2012/10
Times Cited Count:13 Percentile:73.09(Chemistry, Multidisciplinary)Sasaki, Takuo*; Shimomura, Kenichi*; Suzuki, Hidetoshi*; Takahashi, Masamitsu; Kamiya, Itaru*; Oshita, Yoshio*; Yamaguchi, Masafumi*
Japanese Journal of Applied Physics, 51(2), p.02BP01_1 - 02BP01_3, 2012/02
Times Cited Count:2 Percentile:8.71(Physics, Applied)Sasaki, Takuo*; Suzuki, Hidetoshi*; Inagaki, Makoto*; Ikeda, Kazuma*; Shimomura, Kenichi*; Takahashi, Masamitsu; Kozu, Miwa*; Hu, W.; Kamiya, Itaru*; Oshita, Yoshio*; et al.
IEEE Journal of Photovoltaics, 2(1), p.35 - 40, 2012/01
Times Cited Count:5 Percentile:22.06(Energy & Fuels)Sasaki, Takuo*; Suzuki, Hidetoshi*; Takahashi, Masamitsu; Oshita, Yoshio*; Kamiya, Itaru*; Yamaguchi, Masafumi*
Journal of Applied Physics, 110(11), p.113502_1 - 113502_7, 2011/12
Times Cited Count:12 Percentile:45.97(Physics, Applied)Sasaki, Takuo*; Suzuki, Hidetoshi*; Sai, Akihisa*; Takahashi, Masamitsu; Fujikawa, Seiji; Kamiya, Itaru*; Oshita, Yoshio*; Yamaguchi, Masafumi*
Journal of Crystal Growth, 323(1), p.13 - 16, 2011/05
Times Cited Count:20 Percentile:82.65(Crystallography)Growth temperature dependence of strain relaxation during InGaAs/GaAs(001) molecular beam epitaxy was studied by in situ X-ray reciprocal space mapping. Evolution of the residual strain and crystal quality for the InGaAs film was obtained as a function of film thickness at growth temperatures of 420, 445 and 477 C. In the early stages of strain relaxation, it was found that evolution of the residual strain and crystal quality was dependent on the growth temperature. In order to discuss this observation quantitatively, the strain relaxation model was proposed based on the Dodson-Tsao kinetic model, and its validity was demonstrated by good agreement with the experimental residual strain. Additionally, rate coefficients reflecting dislocation motions during strain relaxation were obtained as a function of growth temperature and strain relaxation was discussed in terms of the thermally active dislocation motion.
Elfiky, D.*; Yamaguchi, Masafumi*; Sasaki, Takuo*; Takamoto, Tatsuya*; Morioka, Chiharu*; Imaizumi, Mitsuru*; Oshima, Takeshi; Sato, Shinichiro; Elnawawy, M.*; Eldesoky, T.*; et al.
Japanese Journal of Applied Physics, 49(12), p.121201_1 - 121201_7, 2010/12
Times Cited Count:12 Percentile:45.18(Physics, Applied)One of the fundamental objectives for research and development of space solar cells is to improve their radiation resistance. InGaP solar cells with low base carrier concentrations under low-energy proton irradiations have shown high radiation resistances. In this study, an analytical model for low-energy proton radiation damage to InGaP subcells based on a fundamental approach for radiative and nonradiative recombinations has been proposed. The radiation resistance of InGaP subcells as a function of base carrier concentration has been analyzed by using the radiative recombination lifetime and damage coefficient K for the minority-carrier lifetime of InGaP. Numerical analysis shows that an InGaP solar cell with a lower base carrier concentration is more radiation-resistant. Satisfactory agreements between analytical and experimental results have been obtained, and these results show the validity of the analytical procedure. The damage coefficients for minority-carrier diffusion length and carrier removal rate with low-energy proton irradiations have been observed to be dependent on carrier concentration through this study. As physical mechanisms behind the difference observed between the radiation-resistant properties of various base doping concentrations, two mechanisms, namely, the effect of a depletion layer as a carrier collection layer and generation of the impurity-related complex defects due to low-energy protons stopping within the active region, have been proposed.
Elfiky, D.*; Yamaguchi, Masafumi*; Sasaki, Takuo*; Takamoto, Tatsuya*; Morioka, Chiharu*; Imaizumi, Mitsuru*; Oshima, Takeshi; Sato, Shinichiro; Elnawawy, M.*; Eldesoky, T.*; et al.
Japanese Journal of Applied Physics, 49(12), p.121202_1 - 121202_5, 2010/12
Times Cited Count:8 Percentile:33.83(Physics, Applied)GaAs solar cells with the lower base carrier concentration under low energy proton irradiations had shown experimentally the better radiation-resistance. Analytical model based on fundamental approach for radiative and non-radiative recombination has been proposed for radiation damage in GaAs sub-cells. The radiation resistance of GaAs sub-cells as a function of base carrier concentration has been analyzed by using radiative recombination lifetime and damage coefficient for minority carrier lifetime. Numerical analysis shows good agreement with experimental results. The effect of carrier concentration upon the change of damage constant and carrier removal rate have been studied.
Suzuki, Hidetoshi*; Sasaki, Takuo*; Sai, Akihisa*; Oshita, Yoshio*; Kamiya, Itaru*; Yamaguchi, Masafumi*; Takahashi, Masamitsu; Fujikawa, Seiji
Applied Physics Letters, 97(4), p.041906_1 - 041906_3, 2010/07
Times Cited Count:32 Percentile:74.42(Physics, Applied)Elfiky, D.*; Yamaguchi, Masafumi*; Sasaki, Takuo*; Takamoto, Tatsuya*; Morioka, Chiharu*; Imaizumi, Mitsuru*; Oshima, Takeshi; Sato, Shinichiro; Elnawawy, M.*; Eldesuky, T.*; et al.
Proceedings of 35th IEEE Photovoltaic Specialists Conference (PVSC-35) (CD-ROM), p.002528 - 002532, 2010/06
Times Cited Count:7 Percentile:88.90(Energy & Fuels)Proton energy dependence of radiation damage to GaAs/Ge solar cells irradiated with protons with various energies (50 keV, 200 keV, 1 MeV and 9.5 MeV) were analyzed by using PC1D simulation together with SRIM simulations to investigate their electrical properties. The degradation of the open-circuit voltage is highest for 50 keV irradiation and lowest for 9.5 MeV irradiation. According to SRIM simulations the above changes in electrical properties are mainly related to damage in different regions of the solar sells.
Sasaki, Takuo*; Suzuki, Hidetoshi*; Sai, Akihisa*; Takahashi, Masamitsu; Fujikawa, Seiji; Oshita, Yoshio*; Yamaguchi, Masafumi*
Materials Research Society Symposium Proceedings, Vol.1268, 6 Pages, 2010/05
Times Cited Count:0 Percentile:0.00(Materials Science, Multidisciplinary)Okuchi, Takuo*; Sasaki, Shigeo*; Osakabe, Toyotaka; Ono, Yoshiki*; Odake, Shoko*; Kagi, Hiroyuki*
Journal of Physics; Conference Series, 215, p.012188_1 - 012188_9, 2010/03
Times Cited Count:5 Percentile:84.82(Instruments & Instrumentation)We prepared super-hard nano-polycrystalline diamond (NPD) anvils for large-volume compression for intrinsically low-sensitivity methods of measurement, such as neutron scattering and NMR. These anvils are harder, larger and stronger than single crystal diamond anvils, so that they could play an ideal role to accept the larger forces. We tested supported and unsupported anvil geometries separately by using two types of compact high-pressure cells and could generate the pressure of 14 GPa for the sample volume of 0.1 mm or more. The test results demonstrate a large future potential of NPD anvils for large-volume compression.