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Kaneko, Koji; Tabata, Chihiro; Hagihara, Masato; Yamauchi, Hiroki; Kubota, Masato; Osakabe, Toyotaka; Onuki, Yoshichika*
Journal of the Physical Society of Japan, 92(8), p.085001_1 - 085001_2, 2023/08
Times Cited Count：0 Percentile：0(Physics, Multidisciplinary)Kubota, Masato
Isotope News, (771), p.40 - 42, 2020/10
no abstracts in English
Kubota, Masato; Nigo, Seisuke*; Kato, Seiichi*; Amemiya, Kenta*
AIP Advances (Internet), 9(9), p.095050_1 - 095050_4, 2019/09
Times Cited Count：1 Percentile：4.41(Nanoscience & Nanotechnology)We measured the X-ray absorption spectra of amorphous alumina with vacancy-type oxygen defects which exhibits the resistance random access memory effect. For the first time, we detected changes in the electronic structure owing to the memory effect. A major difference in spectrum was observed near the O K-absorption edge.
Kubota, Masato; Sakurai, Takeaki*; Miyadera, Tetsuhiko*; Nakao, Hironori*; Sugita, Takeshi*; Yoshida, Yuji*
Journal of Applied Physics, 120(16), p.165501_1 - 165501_5, 2016/10
Times Cited Count：0 Percentile：0(Physics, Applied)We performed soft X-ray resonant scattering experiments on P3HT:PCBM blend thin films to reveal the domain structure and electronic state, where P3HT and PCBM mean regioregular poly (3-hexylthiophene) and [6,6]-phenyl-C61-buteric acid methyl ester, respectively. We measured two films, where chloroform (CF sample) and 1,2-dichlorobenzene (DCB sample) are used as solvents in the fabrication process. There is negligible X-ray incident angle dependence of the X-ray absorption spectra at the S 
-absorption edge in the CF sample, whereas the DCB sample exhibits clear incident angle dependence. We obtained the wave-number resolved spectra at 
= (1, 0, 0) for P3HT molecules in both samples. The packing growth of P3HT molecules is revealed to be much more developed in the DCB sample than the CF sample. In addition, the electronic structure at local sulfur element sites clearly changes for both of the samples.
Sakaguchi, Yoshifumi*; Asaoka, Hidehito; Uozumi, Yuki; Kawakita, Yukinobu; Ito, Takayoshi*; Kubota, Masato; Yamazaki, Dai; Soyama, Kazuhiko; Sheoran, G.*; Mitkova, M.*
Physica Status Solidi (A), 213(7), p.1894 - 1903, 2016/07
Times Cited Count：7 Percentile：34.12(Materials Science, Multidisciplinary)no abstracts in English
Sakaguchi, Yoshifumi*; Asaoka, Hidehito; Uozumi, Yuki; Kawakita, Yukinobu; Ito, Takayoshi*; Kubota, Masato; Yamazaki, Dai; Soyama, Kazuhiko; Ailavajhala, M.*; Wolf, K.*; et al.
JPS Conference Proceedings (Internet), 8, p.031023_1 - 031023_6, 2015/09
We report recent results of time-resolved neutron reflectivity measurements for silver photo-diffusion into Ge
S
(x=0.20, 0.33, 0.40) films performed on BL17 (SHARAKU). It is well known that silver diffuses into Ge-chalcogenide layer by visible light exposure with a distinct diffusion front, where the silver concentration abruptly drops off. Using an event recording system at the Materials and Life Science Experimental Facility, neutron reflectivity profiles were collected with a time-resolution of 30 seconds in the shortest case. It was found from the measurements that a relatively stable Ag-rich phase in the reaction layer is firstly formed, and then, slower diffusion occurs at the interface between Ag-rich and Ag-poor layers. Fourier transform analysis showed that the position of the interface is essentially fixed. This result is in contrast to the previously reported model of silver diffusion that postulates a mechanism involving progression of the diffusion front. The results of the measurements on Ag/Ge-Se films performed on the INTER instrument at ISIS are also reported.
Sakaguchi, Yoshifumi*; Asaoka, Hidehito; Uozumi, Yuki; Kawakita, Yukinobu; Ito, Takayoshi*; Kubota, Masato; Yamazaki, Dai; Soyama, Kazuhiko; Ailavajhala, M.*; Latif, M. R.*; et al.
Journal of Physics; Conference Series, 619(1), p.012046_1 - 012046_4, 2015/06
Times Cited Count：8 Percentile：95.66(Engineering, Electrical & Electronic)We report the results of time-resolved neutron reflectivity measurements of Ag/a- Ge
S
/Si and a- Ge
Se
/Ag/ Si films taken while the films are exposed to visible light. Silver diffuses into an amorphous (a-) chalcogenide layer while visible light illuminates Ag/a-chalcogenide films. Neutron reflectometry is a suitable technique probing time evolution of the multi-layer structure without damaging the sample by the probe beam itself. It was found from the measurements of Ag/a-GeS/Si films that a relatively stable Ag-rich phase in the reaction layer is first formed, and then, slower diffusion occurs at the interface between Ag-rich and Ag-poor layers. This result is in contrast to the previously reported model of silver diffusion that suggests a mechanism involving progression of the diffusion front. From the measurements of a-GeSe/Ag/ Si films, we found enormous changes in the neutron reflectivity profile, including loss of total reflection region, with continuous illumination even after forming one homogeneous layer, which was about 60 min after starting illumination. At this stage, clear off-specular scattering was observed by a linear detector and a surface roughness was observed with naked eyes.
S (
=0.2 and 0.4) films using neutron reflectometrySakaguchi, Yoshifumi*; Asaoka, Hidehito; Uozumi, Yuki; Kawakita, Yukinobu; Ito, Takayoshi*; Kubota, Masato; Yamazaki, Dai; Soyama, Kazuhiko; Ailavajhala, M.*; Latif, R.*; et al.
Canadian Journal of Physics, 92(7/8), p.654 - 658, 2014/07
Times Cited Count：12 Percentile：62.3(Physics, Multidisciplinary)We report our recent results of neutron reflectivity measurements for Ag/a-Ge S (x=0.2, 0.4) films under light illumination. The neutron reflectivity measurements have been performed on a polarized neutron reflectometer (BL17, SHARAKU) at Japan Proton Accelerator Research Complex (J-PARC), Japan. By using the time-of flight instrument with intensive pulsed neutrons produced by 300kW proton beams, time evolution of the neutron reflectivity under a light illumination has been revealed, with at least 2-min time resolution. From the detailed analysis, it was found for Ag 50nm/Ge S 150nm films under a light illumination from the Ag layer side that there are two types of diffusion processes: a fast change observed in the first 10 min after illumination using a xenon lamp, which is then followed by a slow change observed after a 1 hour of additional light exposure. The result indicates that there is a comparatively stable (metastable) state in the Ag-doped Ge S layer in terms of Ag composition, and the next silver diffusion process occurs by affecting the Ag-doped Ge S layer / interface. This coincides with the Ge S results of Wagner et al. obtained for Ag/As-S films. These results are also in accord with the results reported by some of us by modeling of the Ag transport in Ge-Se glass showing the presence of slow and fast moving Ag ions. Our result demonstrated that the idea of a two-step reaction process can be applied to Ge-chalcogenide system. We also discuss illumination-side dependence and Ge-composition dependence of reaction process.
)
(SrMnO) superlattice revealed by resonant soft X-ray scatteringKubota, Masato; Yamada, Hiroyuki*; Nakao, Hironori*; Okamoto, Jun*; Yamasaki, Yuichi*; Sawa, Akihito*; Murakami, Yoichi*
Japanese Journal of Applied Physics, 53(5S1), p.05FH07_1 - 05FH07_5, 2014/05
Times Cited Count：2 Percentile：8.84(Physics, Applied)
high-spin state with a large orbital angular momentum in La
Ca
CoO
Okamoto, Jun*; Nakao, Hironori*; Yamasaki, Yuichi*; Wadachi, Hiroki*; Tanaka, Arata*; Kubota, Masato; Horigane, Kazumasa*; Murakami, Yoichi*; Yamada, Kazuyoshi*
Journal of the Physical Society of Japan, 83(4), p.044705_1 - 044705_6, 2014/04
Times Cited Count：9 Percentile：55.36(Physics, Multidisciplinary)Nigo, Seisuke*; Kubota, Masato; Harada, Yoshitomo*; Hirayama, Taisei*; Kato, Seiichi*; Kitazawa, Hideaki*; Kido, Giyu*
Journal of Applied Physics, 112(3), p.033711_1 - 033711_6, 2012/08
Times Cited Count：61 Percentile：89.42(Physics, Applied)Takeda, Masayasu; Yamazaki, Dai; Soyama, Kazuhiko; Maruyama, Ryuji; Hayashida, Hirotoshi; Asaoka, Hidehito; Yamazaki, Tatsuya; Kubota, Masato; Aizawa, Kazuya; Arai, Masatoshi; et al.
Chinese Journal of Physics, 50(2), p.161 - 170, 2012/04
; Comparison with LaFePONishi, Ichiro*; Ishikado, Motoyuki; Ideta, Shinichiro*; Malaeb, W.*; Yoshida, Teppei*; Fujimori, Atsushi*; Kotani, Yoshinori*; Kubota, Masato*; Ono, Kanta*; Yi, M.*; et al.
Physical Review B, 84(1), p.014504_1 - 014504_5, 2011/07
Times Cited Count：22 Percentile：65.72(Materials Science, Multidisciplinary)We have performed an angle-resolved photoemission spectroscopy (ARPES) study of the iron-based superconductor PrFeAsO and examined the Fermi surfaces and band dispersions near the fermi level. Heavily hole-doped electronic states have been observed due to the polar nature of the cleaved surfaces. Nevertheless, we have found that the ARPES spectra basically agree with band dispersions calculated in the local density approximation (LDA) if the bandwidth is reduced by a factor of 
2.5 and then the chemical potential is lowered by 70 meV. Comparison with previous ARPES results on LaFePO reveals that the energy positions of the 
- and 
-derived bands are considerably different between the two materials, which we attribute to the different pnictogen height as predicted by the LDA calculation.
Osakabe, Toyotaka; Kogi, Masafumi*; Iwasa, Kazuaki*; Kubota, M.*; Yoshizawa, Hideki*; Haga, Yoshinori; Suzuki, T.*
Physica B; Condensed Matter, 281-282, p.434 - 436, 2000/06
Times Cited Count：5 Percentile：32.8(Physics, Condensed Matter)no abstracts in English
Osakabe, Toyotaka; *; Iwasa, Kazuaki*; Kakurai, Kazuhisa*; J.-M.Mignot*; I.Goncharenko*; *; Takahashi, Hiroki*; Mori, Nobuo*; Kubota, M.*; et al.
Physics of Strongly Correlated Electron Systems (JJAP Series 11), p.123 - 125, 1998/00
no abstracts in English
O studied by use of synchrotron radiationKubota, Masato*; Hayakawa, Hironori*; Oishi, Daisuke*; Akahama, Yuji*; Yoshii, Kenji; Kambe, Takashi*; Ikeda, Naoshi*
no journal, ,
Charge-ordered state of electronic ferroelectric LuFeO was studied by use of synchrotron radiation. We have performed X-ray diffraction measurements at Fe K- and L-edges for a single-crystal LuFe with applying currents at around room temperature. It was observed that the charge-ordered state changed depending on parameters such as the current density and the direction of current. We will discuss detailed results of experiments and at the conference.
OHayakawa, Hironori*; Kubota, Masato*; Oishi, Daisuke*; Akahama, Yuji*; Matsuo, Yoji*; Ikeda, Naoshi*; Kambe, Takashi*; Kimizuka, Noboru*; Yoshii, Kenji
no journal, ,
We have investigated the change of charge-ordered state in LuFeO caused by an applied electric field. The application of the field above a threshold led to a drastic decrease in resistivity; this behavior corresponds to the change of charge-ordered structure observed using synchrotron radiation. More details will be shown at the conference.
Takeda, Masayasu; Yamazaki, Dai; Soyama, Kazuhiko; Maruyama, Ryuji; Hayashida, Hirotoshi; Asaoka, Hidehito; Yamazaki, Tatsuya; Kubota, Masato; Aizawa, Kazuya; Inamura, Yasuhiro; et al.
no journal, ,
Kaneko, Koji; Kubota, Masato; Osakabe, Toyotaka; Takeda, Masayasu; Wakimoto, Shuichi; Yamauchi, Hiroki
no journal, ,
Kubota, Masato
no journal, ,
no abstracts in English
