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171 results on '"Takahasi, Masamitu"'

9. Design of nano-spintronics beamline at 3-GeV next-generation synchrotron radiation facility, NanoTerasu

Author

Ohtsubo, Yoshiyuki, primary, Ueno, Tetsuro, additional, Iwasawa, Hideaki, additional, Miyawaki, Jun, additional, Horiba, Koji, additional, Inaba, Kento, additional, Agui, Akane, additional, Inami, Nobuhito, additional, Nakatani, Takeshi, additional, Imazono, Takashi, additional, Fujii, Kentaro, additional, Kimura, Hiroaki, additional, and Takahasi, Masamitu, additional

Published
2022
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10. Design of Ultrahigh Energy Resolution RIXS Beamline at NanoTerasu

Author

Miyawaki, Jun, primary, Fujii, Kentaro, additional, Imazono, Takashi, additional, Horiba, Koji, additional, Ohtsubo, Yoshiyuki, additional, Inami, Nobuhito, additional, Nakatani, Takeshi, additional, Inaba, Kento, additional, Agui, Akane, additional, Kimura, Hiroaki, additional, and Takahasi, Masamitu, additional

Published
2022
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15. X-ray reflectivity and diffraction studies on lipid and lipopolymer Langmuir-Blodgett films under controlled humidity

Author

Bolze, Jorg, Takahasi, Masamitu, Junichiro, Mizuki, Baumgart, Tobias, and Knoll, Wolfgang

Subjects
Synchrotron radiation -- Usage, Cephalin -- Chemical properties, Chemistry
Abstract

The characterization of distearoylphosphatidylethanolamine (DSPE) and DSPE-PEO Langmuir-Blodgett films by x-ray reflectivity and grazing incidence x-ray diffraction using synchrotron radiation is discussed. There were indications for a significant intermixing of the polymer with the DSPE moieties, probably resulting in the formation of hydrophobic nanodomains of closely packed alkyl chains that are immersed into the hydrated polymer.

Published
2002

21. Surface study of organopalladium molecules on S-terminated GaAs

Author

Konishi, Tomoya, Nishiwaki, Nagatoshi, Toujyou, Takashi, Ishikawa, Takuma, Teraoka, Teruki, Ueta, Yukiko, Kihara, Yoshifumi, Moritoki, Hideji, Tono, Tatsuo, Musashi, Mio, Tada, Takashi, Fujikawa, Seiji, Takahasi, Masamitu, Bell, Gavin, Shimoda, Masahiko, Tsukamoto, Shiro, Konishi, Tomoya, Nishiwaki, Nagatoshi, Toujyou, Takashi, Ishikawa, Takuma, Teraoka, Teruki, Ueta, Yukiko, Kihara, Yoshifumi, Moritoki, Hideji, Tono, Tatsuo, Musashi, Mio, Tada, Takashi, Fujikawa, Seiji, Takahasi, Masamitu, Bell, Gavin, Shimoda, Masahiko, and Tsukamoto, Shiro

Abstract

Organopalladium species ({Pd}) immobilized on an Sterminated GaAs substrate (S/GaAs) effectively catalyzes C-C bond formation in the Mizoroki-Heck reaction with cycle durability. However, the immobilizing mechanism of {Pd} is unknown. In this study, we deposited Pd(OCOCH3)2 on S/GaAs in two different methods, namely dry-physical vapor-deposition and wetchemical deposition, and compared the catalytic activities in the Mizoroki-Heck reaction. Also, S-termination and {Pd}-immobilization on GaAs grains were performed by the wet-chemical method to monitor the change in the surface chemical structure during the preparation process with diffuse reflectance Fourier transform infrared spectroscopy (FT-IR). FT-IR measurements implied that the immobilization of catalytic active {Pd} was related to the OH groups on the S-terminated surface. {Pd}-S/GaAs prepared dryphysically showed poor catalytic activity, because {Pd} was not immobilized under absence of OH groups.

Published
2019

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

Author

Sasaki, Takuo, Suzuki, Hidetoshi, Takahasi, Masamitu, Ohshita, Yoshio, Kamiya, Itaru, and Yamaguchi, Masafumi

Subjects
ELECTRIC properties of thin films, INDIUM gallium arsenide, GALLIUM arsenide, DISLOCATIONS in crystals, THICKNESS measurement, HYBRID systems, MOLECULAR beam epitaxy, X-ray diffraction
Abstract

Dislocation-mediated strain relaxation during lattice-mismatched InGaAs/GaAs(001) heteroepitaxy was studied through in situ x-ray reciprocal space mapping (in situ RSM). At the synchrotron radiation facility SPring-8, a hybrid system of molecular beam epitaxy and x-ray diffractometry with a two-dimensional detector enabled us to perform in situ RSM at high-speed and high-resolution. Using this experimental setup, four results in terms of film properties were simultaneously extracted as functions of film thickness. These were the lattice constants, the diffraction broadenings along in-plane and out-of-plane directions, and the diffuse scattering. Based on correlations among these results, the strain relaxation processes were classified into four thickness ranges with different dislocation behavior. In addition, the existence of transition regimes between the thickness ranges was identified. Finally, the dominant dislocation behavior corresponding to each of the four thickness ranges and transition regimes was noted. [ABSTRACT FROM AUTHOR]

Published
2011
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31. Temperature dependence of liquid-gallium ordering on the surface of epitaxially grown GaN

Author

Sasaki, Takuo, Iwata, Takuya, Sugitani, Kanya, Kawamura, Takahiro, Akiyama, Toru, and Takahasi, Masamitu

Abstract

The three-dimensional ordering of the gallium (Ga) adlayers on GaN(0001) and (0001¯) surfaces was probed using in situ X-ray scattering under MBE conditions. An ordered bilayer of Ga forms on GaN(0001) but the ordering decreases at substrate temperatures of <450 °C, consistent with the mechanism of non-equilibrium epitaxial growth. Monolayer Ga that forms on GaN(0001¯) is laterally disordered and has no temperature dependence, along with droplets of excess Ga. The vertical and lateral B-factors for each Ga layer were confirmed using first-principles molecular dynamics calculations.

Published
2024
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45. In Situ Electrochemical, Electrochemical Quartz Crystal Microbalance, Scanning Tunneling Microscopy, and Surface X-ray Scattering Studies on Ag/AgCl Reaction at the Underpotentially Deposited Ag Bilayer on the Au(111) Electrode Surface

Author

1000020133697, Uosaki, Kohei, Morita, Jun, Katsuzaki, Tomoko, Takakusagi, Satoru, Tamura, Kazuhisa, Takahasi, Masamitu, Mizuki, Jun'ichiro, Kondo, Toshihiro, 1000020133697, Uosaki, Kohei, Morita, Jun, Katsuzaki, Tomoko, Takakusagi, Satoru, Tamura, Kazuhisa, Takahasi, Masamitu, Mizuki, Jun'ichiro, and Kondo, Toshihiro

Abstract

Ag/AgCl reaction at the Ag bilayer, which was underpotentially prepared on a Au(111) surface, was investigated using electrochemical quartz crystal microbalance (EQCM), scanning tunneling microscopy (STM), surface X-ray scattering (SXS), and electrochemical techniques. When the potential was scanned positively from -200 mV, the Cl^[-] ion was adsorbed on the Au(111) electrode surface around 0 mV, and then the phase transition of the adsorbed Cl^[-] ion layer from random orientation to (√3 x √3) structure took place at around +130 mV. The Ag bilayer and Cl^[-] ions were oxidatively reacted to form the AgCl monolayer with (√13 x √13)R13.9° structure around +200 mV, accompanied with the formation of AgCl monocrystalline clusters on the AgCl monolayer surface. The structure of the AgCl monolayer on the Au(111) surface was changed from (√13 x √13)R13.9° structure to (4 x 4) structure around +500 mV. When the potential was scanned back negatively, the AgCl monolayer was electrochemically reduced, and a Ag monolayer, not a bilayer, was formed on the Au(111) surface. In the subsequent potential cycles, the structural change between the Ag monolayer and the AgCl monolayer was reversibly observed. All oxidative structural changes were much slower than the reductive ones.

Published
2011

46. In Situ Electrochemical, Electrochemical Quartz Crystal Microbalance, Scanning Tunneling Microscopy, and Surface X-ray Scattering Studies on Ag/AgCl Reaction at the Underpotentially Deposited Ag Bilayer on the Au(111) Electrode Surface

Author

Uosaki, Kohei, Morita, Jun, Katsuzaki, Tomoko, Takakusagi, Satoru, Tamura, Kazuhisa, Takahasi, Masamitu, Mizuki, Jun'ichiro, Kondo, Toshihiro, Uosaki, Kohei, Morita, Jun, Katsuzaki, Tomoko, Takakusagi, Satoru, Tamura, Kazuhisa, Takahasi, Masamitu, Mizuki, Jun'ichiro, and Kondo, Toshihiro

Abstract

Ag/AgCl reaction at the Ag bilayer, which was underpotentially prepared on a Au(111) surface, was investigated using electrochemical quartz crystal microbalance (EQCM), scanning tunneling microscopy (STM), surface X-ray scattering (SXS), and electrochemical techniques. When the potential was scanned positively from -200 mV, the Cl^[-] ion was adsorbed on the Au(111) electrode surface around 0 mV, and then the phase transition of the adsorbed Cl^[-] ion layer from random orientation to (√3 x √3) structure took place at around +130 mV. The Ag bilayer and Cl^[-] ions were oxidatively reacted to form the AgCl monolayer with (√13 x √13)R13.9° structure around +200 mV, accompanied with the formation of AgCl monocrystalline clusters on the AgCl monolayer surface. The structure of the AgCl monolayer on the Au(111) surface was changed from (√13 x √13)R13.9° structure to (4 x 4) structure around +500 mV. When the potential was scanned back negatively, the AgCl monolayer was electrochemically reduced, and a Ag monolayer, not a bilayer, was formed on the Au(111) surface. In the subsequent potential cycles, the structural change between the Ag monolayer and the AgCl monolayer was reversibly observed. All oxidative structural changes were much slower than the reductive ones.

Published
2011

47. Surface study of organopalladium molecules on S-terminated GaAs

Author

Konishi, Tomoya, Nishiwaki, Nagatoshi, Toujyou, Takashi, Ishikawa, Takuma, Teraoka, Teruki, Ueta, Yukiko, Kihara, Yoshifumi, Moritoki, Hideji, Tono, Tatsuo, Musashi, Mio, Tada, Takashi, Fujikawa, Seiji, Takahasi, Masamitu, Bell, Gavin, Shimoda, Masahiko, Tsukamoto, Shiro, Konishi, Tomoya, Nishiwaki, Nagatoshi, Toujyou, Takashi, Ishikawa, Takuma, Teraoka, Teruki, Ueta, Yukiko, Kihara, Yoshifumi, Moritoki, Hideji, Tono, Tatsuo, Musashi, Mio, Tada, Takashi, Fujikawa, Seiji, Takahasi, Masamitu, Bell, Gavin, Shimoda, Masahiko, and Tsukamoto, Shiro

Abstract

Organopalladium species ({Pd}) immobilized on an Sterminated GaAs substrate (S/GaAs) effectively catalyzes C-C bond formation in the Mizoroki-Heck reaction with cycle durability. However, the immobilizing mechanism of {Pd} is unknown. In this study, we deposited Pd(OCOCH3)2 on S/GaAs in two different methods, namely dry-physical vapor-deposition and wetchemical deposition, and compared the catalytic activities in the Mizoroki-Heck reaction. Also, S-termination and {Pd}-immobilization on GaAs grains were performed by the wet-chemical method to monitor the change in the surface chemical structure during the preparation process with diffuse reflectance Fourier transform infrared spectroscopy (FT-IR). FT-IR measurements implied that the immobilization of catalytic active {Pd} was related to the OH groups on the S-terminated surface. {Pd}-S/GaAs prepared dryphysically showed poor catalytic activity, because {Pd} was not immobilized under absence of OH groups., journal article

Published
2011

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