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Journal Articles

Effects of growth temperature and growth rate on polytypes in gold-catalyzed GaAs nanowires studied by in situ X-ray diffraction

Takahashi, Masamitsu; Kozu, Miwa*; Sasaki, Takuo

Japanese Journal of Applied Physics, 55(4S), p.04EJ04_1 - 04EJ04_4, 2016/04

 Times Cited Count:4 Percentile:25.92(Physics, Applied)

Journal Articles

Anomalous lattice deformation in GaN/SiC(0001) measured by high-speed ${{it in situ}}$ synchrotron X-ray diffraction

Sasaki, Takuo; Ishikawa, Fumitaro*; Takahashi, Masamitsu

Applied Physics Letters, 108(1), p.012102_1 - 012102_5, 2016/01

AA2015-0769.pdf:2.43MB

 Times Cited Count:1 Percentile:6.36(Physics, Applied)

Journal Articles

Direct observation of strain in InAs quantum dots and cap layer during molecular beam epitaxial growth using ${{it in situ}}$ X-ray diffraction

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:7 Percentile:37.13(Physics, Applied)

Journal Articles

Mechanisms determining the structure of gold-catalyzed GaAs nanowires studied by in situ X-ray diffraction

Takahashi, Masamitsu; Kozu, Miwa*; Sasaki, Takuo; Hu, W.*

Crystal Growth & Design, 15(10), p.4979 - 4985, 2015/10

 Times Cited Count:12 Percentile:73.32(Chemistry, Multidisciplinary)

Journal Articles

Strain analysis of III-V epitaxial growth by ${{it in situ}}$ synchrotron X-ray diffraction

Sasaki, Takuo; Takahashi, Masamitsu

Nihon Kessho Seicho Gakkai-Shi, 42(3), p.210 - 217, 2015/10

AA2015-0738.pdf:2.23MB

Journal Articles

${it In situ}$ three-dimensional X-ray reciprocal-space mapping of InGaAs multilayer structures grown on GaAs(001) by MBE

Sasaki, Takuo; Takahashi, Masamitsu; Suzuki, Hidetoshi*; Oshita, Yoshio*; Yamaguchi, Masafumi*

Journal of Crystal Growth, 425, p.13 - 15, 2015/09

 Times Cited Count:3 Percentile:34(Crystallography)

Journal Articles

Role of liquid indium in the structural purity of wurtzite InAs nanowires that grow on Si(111)

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:24 Percentile:75.15(Chemistry, Multidisciplinary)

Journal Articles

Defect characterization in compositionally graded InGaAs layers on GaAs (001) grown by MBE

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:3 Percentile:81.12

Journal Articles

Real-time observation of crystallographic tilting InGaAs layers on GaAs offcut substrates

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:0.01

Journal Articles

High-speed three-dimensional reciprocal-space mapping during molecular beam epitaxy growth of InGaAs

Hu, W.; Suzuki, Hidetoshi*; Sasaki, Takuo*; Kozu, Miwa*; Takahashi, Masamitsu

Journal of Applied Crystallography, 45(5), p.1046 - 1053, 2012/10

 Times Cited Count:10 Percentile:70.93(Chemistry, Multidisciplinary)

Journal Articles

Observation of in-plane asymmetric strain relaxation during crystal growth and growth interruption in InGaAs/GaAs(001)

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:10.01(Physics, Applied)

Journal Articles

Real-time structural analysis of compositionally graded InGaAs/GaAs(001) layers

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:25.16(Energy & Fuels)

Journal Articles

X-ray reciprocal space mapping of dislocation-mediated strain relaxation during InGaAs/GaAs(001) epitaxial growth

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:11 Percentile:47.47(Physics, Applied)

Journal Articles

Growth temperature dependence of strain relaxation during InGaAs/GaAs(0 0 1) heteroepitaxy

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:17 Percentile:82.2(Crystallography)

Growth temperature dependence of strain relaxation during In$$_{0.12}]$$Ga$$_{0.88}$$As/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 $$^{circ}$$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.

Journal Articles

Theoretical optimization of base doping concentration for radiation resistance of InGaP subcells of InGaP/GaAs/Ge based on minority-carrier lifetime

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:10 Percentile:43.19(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.

Journal Articles

Effect of base doping concentration on radiation-resistance for GaAs sub-cells in InGaP/GaAs/Ge

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:6 Percentile:29.58(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.

Journal Articles

Real-time observation of anisotropic strain relaxation by three-dimensional reciprocal space mapping during InGaAs/GaAs(001) growth

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:30 Percentile:76.37(Physics, Applied)

Journal Articles

Study the effects of proton irradiation on GaAs/Ge solar cells

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:1 Percentile:61.53

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.

Journal Articles

In situ study of strain relaxation mechanisms during lattice-mismatched InGaAs/GaAs growth by X-ray reciprocal space mapping

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:0.01

Journal Articles

Large-volume static compression using nano-polycrystalline diamond for opposed anvils in compact cells

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:87.1

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$$^{3}$$ or more. The test results demonstrate a large future potential of NPD anvils for large-volume compression.

49 (Records 1-20 displayed on this page)