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Journal Articles

Phase-change materials; Vibrational softening upon crystallization and its impact on thermal properties

Matsunaga, Toshiyuki*; Yamada, Noboru*; Kojima, Rie*; Shamoto, Shinichi; Sato, Masugu*; Tanida, Hajime*; Uruga, Tomoya*; Kohara, Shinji*; Takata, Masaki*; Zalden, P.*; et al.

Advanced Functional Materials, 21(12), p.2232 - 2239, 2011/06

 Times Cited Count:103 Percentile:95.79(Chemistry, Multidisciplinary)

Thermal properties of the amorphous and crystalline state of phase-change materials show remarkable differences such as higher thermal displacements and a more pronounced anharmonic behavior in the crystalline phase. These findings are related to the change of bonding upon crystallization.

Journal Articles

Depth-resolved XAFS analysis of SrTiO$$_3$$ thin film

Yoneda, Yasuhiro; Tanida, Hajime*; Takagaki, Masafumi*; Uruga, Tomoya*

Transactions of the Materials Research Society of Japan, 35(1), p.99 - 102, 2010/03

Depth dependency of local structure of SrTiO$$_3$$ thin film was investigated by X-ray absorption fine structure (XAFS). In epitaxial thin films, a large strain exists between substrates and grown films. The expitaxial strain is the largest in the interface and it is relaxed as parting from the substrate. The lattice parameter of the grown film changes depending on the lattice strain. We performed depth-resolved XAFS measurements on SrTiO$$_3$$ thin film grown on LaAlO$$_3$$ substrate. The depth-resolved XAFS can extract the local structures around the surface and inner regions separately. It was clarified that the bond distance between Sr and O changed greatly depending on the depth. On the other hand, the bond distance between Sr and Ti unchanged.

Journal Articles

Neutron diffraction and X-ray absorption study of Ag$$_{5}$$Pb$$_{2}$$O$$_{6}$$

Yoshii, Kenji; Mizumaki, Masaichiro*; Kato, Kazuo*; Uruga, Tomoya*; Abe, Hideki*; Nakamura, Akio; Shimojo, Yutaka; Ishii, Yoshinobu; Morii, Yukio

Journal of Solid State Chemistry, 180(1), p.377 - 381, 2007/01

 Times Cited Count:6 Percentile:25.64(Chemistry, Inorganic & Nuclear)

no abstracts in English

Journal Articles

Pressure-induced site-selective disordering of Ge$$_{2}$$Sb$$_{2}$$Te$$_{5}$$; A New insight into phase-change optical recording

Kolobov, A.*; Haines, J.*; Pradel, A.*; Ribes, M.*; Fons, P.*; Tominaga, Junji*; Katayama, Yoshinori; Hammounda, T.*; Uruga, Tomoya*

Physical Review Letters, 97(3), p.035701_1 - 035701_4, 2006/07

 Times Cited Count:87 Percentile:92.55(Physics, Multidisciplinary)

We demonstrate that Ge$$_{2}$$Sb$$_{2}$$Te$$_{5}$$ (GST), the material of choice in phase-change optical recording (such as DVD-RAM) can be rendered amorphous by the application of hydrostatic pressure. It is argued that this structural change is due to a very strong second-nearest neighbor Te-Te interaction that determines the long-range order in the metastable cubic phase of GST and also to the presence of vacancies. This newly discovered phenomenon suggests that pressure is an important factor for the formation of the amorphous phase which opens new insight into the mechanism of phase-change optical recording.

Journal Articles

Investigation of structural and electronic properties in Ru perovskite oxides by XAFS measurements

Mizumaki, Masaichiro*; Yoshii, Kenji; Hinatsu, Yukio*; Doi, Yoshihiro*; Uruga, Tomoya*

Physica Scripta, T115, p.513 - 515, 2005/00

The electronic and structural properties of Ru oxides were investigated by utilizing X-ray absorption spectroscopy (XAS). We estimate the valence of Ru in perovskite ruthenium oxides by XAS measurements. XAS measurements were carried out at room temperature around Ru K-edge. The valence of Ru in $$A$$$$_{2}$$ ($$A$$ = Ba, Sr)LnRuO$$_{6}$$ and $$A$$ ($$A$$ = Ca, Ba, Sr)RuO$$_{3}$$ was 4+. The valence of Ru in Ln$$_{3}$$RuO$$_{7}$$ was 5+. The valence of Ru in PbRuO$$_{3}$$ showed an intermediate value between 4+ and 5+. Theoretical calculation reproduced the experimental spectra. We analyzed XAS spectra and obtained information of local structure. The bond length between Ru and O was consistent with the results of neutron diffraction.

Journal Articles

Beamline for surface and interface structures at SPring-8

Sakata, Osami*; Furukawa, Yukito*; Goto, Shunji*; Mochizuki, Tetsuro*; Uruga, Tomoya*; Takeshita, Kunikazu*; Ohashi, Haruhiko*; Ohata, Toru*; Matsushita, Tomohiro*; Takahashi, Sunao*; et al.

Surface Review and Letters, 10(2&3), p.543 - 547, 2003/04

 Times Cited Count:127 Percentile:96.2(Chemistry, Physical)

The main components of a new beamline for surface and interface crystal structure determination at SPring-8 are briefly described. Stages for the beamline monochromator are modified for making an incident X-ray intensity more stable for surface X-ray experiments. Absolute photon flux densities were measured with an incident photon energy. A new ultrahigh vacuum system is introduced with preliminary X-ray measurements from an ordered oxygen on Pt(111) surface.

Journal Articles

Standard X-ray mirror systems for SPring-8 beamlines

Uruga, Tomoya*; Tanida, Hajime*; Yoneda, Yasuhiro; Takeshita, K.*; Goto, Shunji*; Ishikawa, Tetsuya*

Nuclear Instruments and Methods in Physics Research A, 467-468(Part1), p.782 - 784, 2001/07

 Times Cited Count:8 Percentile:54.01(Instruments & Instrumentation)

no abstracts in English

Journal Articles

EXAFS spectra above Pb and Pt $${it K}$$ edges observed at low temperature

Nishihata, Yasuo; Mizuki, Junichiro; Emura, Shuichi*; Uruga, Tomoya*

Journal of Synchrotron Radiation, 8, p.294 - 296, 2001/03

 Times Cited Count:6 Percentile:41.2(Instruments & Instrumentation)

no abstracts in English

Journal Articles

EXAFS study on local structural changes in amorphous Fe-Zr-B alloys

Nakata, Yoshiyuki*; Hara, Naoyuki*; Hirotsu, Yoshihiko*; Emura, Shuichi*; Makino, Akihiro*; Uruga, Tomoya*; Harada, Makoto*; Nishihata, Yasuo; Yoneda, Yasuhiro; Kubozono, Yoshihiro*

Japanese Journal of Applied Physics, 38(Suppl.38-1), p.404 - 407, 1999/06

The EXAFS spectra on Zr K-edge are investigated for as-formed Fe-7at%Zr-3at%B amorphous alloys and annealed ones at 693 K and 773 K for an hour in order to reveal local structural changes due to annealing. The analysis shows that the atomic distances of Fe-Zr and Zr-Zr pairs increase during annealing and approach those in a Fe3Zr or/and Fe2Zr metallic comound. The change in the atomic distances suggests that medium range ordered clusters should be formed during annealing.

Journal Articles

The XAFS beamline BL01B1 at SPring-8

Uruga, Tomoya*; Tanida, Hajime*; Yoneda, Yasuhiro; Takeshita, Kunikazu*; Emura, Shuichi*; Takahashi, Masao*; Harada, Makoto*; Nishihata, Yasuo; Kubozono, Yoshihiro*; Tanaka, Tsunehiro*; et al.

Journal of Synchrotron Radiation, 6(Part3), p.143 - 145, 1999/05

An x-ray absorption fine-structure (XAFS) spectroscopy beamline, BL01B1, was installed at a bending magnet source at SPring-8 and has been open to users since October 1997. It was designed for XAFS experiments covering a wide energy range. Position tables and automatical control programs were established to adjust the x-ray optics and achieve the designed performance of the beamline under each experimental condition. This has enabled conventional XAFS measurements to be made with a good data quality from 4.5 to 110 keV.

Journal Articles

XAFS study on RbC$$_{60}$$

Kubozono, Yoshihiro*; Mimura, Kazue*; Takabayashi, Yasuhiro*; Maeda, Hironobu*; Kashino, Setsuo*; Emura, Shuichi*; Nishihata, Yasuo; Uruga, Tomoya*; Tanaka, Tsunehiro*; Takahashi, Masao*

Journal of Synchrotron Radiation, 6(Part3), p.564 - 566, 1999/05

The Rb K-edge XAFS spectra for the stable phase of RbC60 which is a quasi one-dimensional polymer were measured in the temperature range from 14.6 to 210 K in order to clarify the origin of the metal-insulator transition around 50 K. The distances and mean-square relative displacements between the Rb atom and the neighboring C atoms determined by XAFS exhibited no change around 50 K, implying that the metal-insulator transition originates from the SDW instablity.

Journal Articles

Eu ${it K}$-XAFS of europium dioxymonocyanamide with the convension He$$^+$$ ion yield method

Takahashi, Masao*; Harada, Makoto*; Watanabe, Iwao*; Uruga, Tomoya*; Tanida, Hajime*; Yoneda, Yasuhiro; Emura, Shuichi*; Tanaka, Tsunehiro*; Kimura, Hidekazu*; Kubozono, Yoshihiro*; et al.

Journal of Synchrotron Radiation, 6(3), p.222 - 224, 1999/05

 Times Cited Count:10 Percentile:59.73(Instruments & Instrumentation)

no abstracts in English

Oral presentation

Depth resolved XAFS study on SrTiO$$_3$$ thin film

Yoneda, Yasuhiro; Uruga, Tomoya*; Tanida, Hajime*; Takagaki, Masafumi*

no journal, , 

Depth dependency of local structure of SrTiO$$_3$$ thin film was investigated by X-ray absorption fine structure (XAFS). In epitaxial thin films, a large strain exists between substrates and grown films. The epitaxial strain is the largest in the interface and it is relaxed as parting from the substrate. The lattice parameter of the grown film changes depending on the lattice strain. We performed depth-resolved XAFS measurements on SrTiO$$_3$$ thin film grown on LaAlO$$_3$$ substrate. The depth-resolved XAFS can extract the local structures around the surface and inner regions separately. It was clarified that the bond distance between Sr and O changed greatly depending on the depth. On the other hand, the bond distance between Sr and Ti unchanged.

13 (Records 1-13 displayed on this page)
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