The Physical origin of the InSb(111)A surface reconstruction transient

Proessdorf, A.*; Rodenbach, P.*; Grosse, F.*; Hanke, M.*; Braun, W.*; Riechert, H.*; Hu, W.; Fujikawa, Seiji*; Kozu, Miwa; Takahashi, Masamitsu

Surface Science, 606(17-18), p.1458 - 1461, 2012/09

https://doi.org/10.1016/j.susc.2012.05.017

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

https://doi.org/10.1016/j.jcrysgro.2010.10.005

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.

Structural changes caused by quenching of InAs/GaAs(001) quantum dots

Takahashi, Masamitsu; Fujikawa, Seiji

Japanese Journal of Applied Physics, 50(4), p.04DH06_1 - 04DH06_5, 2011/04

https://doi.org/10.1143/JJAP.50.04DH06

Time-resolved X-ray diffraction measurements of high-density InAs quantum dots on Sb/GaAs layers and the suppression of coalescence by Sb-irradiated growth interruption

Kakuda, Naoki*; Kaizu, Toshiyuki*; Takahashi, Masamitsu; Fujikawa, Seiji; Yamaguchi, Koichi*

Japanese Journal of Applied Physics, 49(9), p.095602_1 - 095602_4, 2010/09

https://doi.org/10.1143/JJAP.49.095602

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

https://doi.org/10.1557/PROC-1268-EE06-02

Electronic and spin states of C-Co compound affecting giant TMR effect, 2

Matsumoto, Yoshihiro; Sakai, Seiji; Entani, Shiro; Nagamatsu, Shinichi*; Hojo, Ikuko*; Fujikawa, Takashi*; Shimada, Toshihiro*; Naramoto, Hiroshi*; Maeda, Yoshihito; Yokoyama, Toshihiko*

no journal, , 

no abstracts in English

Element specific analysis of the molecular spintronics materials using synchrotron radiation

Matsumoto, Yoshihiro; Entani, Shiro; Naramoto, Hiroshi*; Sakai, Seiji; Shimada, Toshihiro*; Yokoyama, Toshihiko*; Fujikawa, Takashi*

no journal, , 

no abstracts in English

X-ray diffraction study on hydrogen-induced Pd(110) surface reconstruction

Takahashi, Masamitsu; Fujikawa, Seiji*; Hu, W.; Tajiri, Hiroo*

no journal, , 

Absorption of hydrogen into a substrate begins with dissociated adsorption of hydrogen molecules. The mechanism of the transition from adsorption to absorption is an important knowledge for improving the performance of hydrogen storage materials. The aim of the present study is to verify the hydrogen absorption model in atomic scale through quantitative determination of structures of hydrogen-adsorbed Pd(110) by synchrotron X-ray diffraction. Experiments were performed at a synchrotron beamline 13XU at SPring-8 using a surface X-ray diffractometer integrated with a UHV chamber equipped with a cryostat. We measured five crystal truncation rod (CTR) profiles with increasing substrate temperature to room temperature from 57 K after the substrate was exposed to 10 Torr s hydrogen. Results show an atomic-scale picture that explains how adsorbed hydrogen is absorbed into the Pd bulk.

X-ray absorption and magnetic circular dichroism signals from hexagonal boron nitride/Ni(111) interface

Otomo, Manabu; Matsumoto, Yoshihiro; Yamamura, Noyuri*; Entani, Shiro; Avramov, P.; Naramoto, Hiroshi*; Amemiya, Kenta*; Fujikawa, Takashi*; Sakai, Seiji

no journal, , 

Graphene has been intensively studied in the last few years for its long spin coherent length. The performance of graphene spintronic devices, however, are strongly influenced by poor spin injection efficiency at graphene/ferromagnetic metal (FM) interface. A promising solution for improving spin injection efficiency is to insert a tunnel barrier between graphene and FM. In this study, we propose hexagonal boron nitride (h-BN) as a novel tunnel barrier for graphene spintronics. It was revealed that the N K-edge and B K-edge absorptions exhibit XMCD signals in response to the Ni magnetization. It was also found that the smaller incidence angle between the Ni magnetization and the X-ray propagation direction leads to larger XMCD signals. The nature of the spin polarization was discussed in connection with the energy and angle dependences of the XMCD signals, and contribution from magnetized Nickel atoms was proposed.

High spin polarization of tunnelling electrons at the interfaces in fullerene-magnetic metal systems

Sakai, Seiji; Matsumoto, Yoshihiro; Otomo, Manabu; Entani, Shiro; Avramov, P.; Naramoto, Hiroshi*; Fujikawa, Takashi*

no journal, ,