ORCID Profile
0000-0001-9596-2680
Current Organisations
Tokyo University of Science
,
National Institute for Materials Science
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Publisher: Informa UK Limited
Date: 03-07-2020
Publisher: IOP Publishing
Date: 08-12-2011
DOI: 10.1088/0953-8984/24/1/015802
Abstract: The structure and electronic properties of amorphous Ge(15)Te(85) have been studied by combining density functional (DF) simulations with high-energy x-ray and neutron diffraction measurements. Three models with 560 atoms have been constructed using reverse Monte Carlo methods constrained to (1) agree with the experimental structure factors S(Q), and have (2) energies close to the DF minimum and (3) a semiconducting band structure. The best structure is based on the melt-quenched DF structure and has a small number of Ge-Ge bonds. It shows interlocking networks of Te and GeTe with a significant fraction (22-24%) of voids (cavities). Ge occurs with both tetrahedral and 3 + 3 defective octahedral configurations, and the coordination of Te is slightly higher than indicated by the '8 - N rule' (N is the number of valence electrons). The GeTe network includes clusters of ABAB squares (A = Ge, B = Te), and the bonding is characterized by the chemical bond orders.
Publisher: Springer Science and Business Media LLC
Date: 30-10-2015
Publisher: Elsevier BV
Date: 11-2011
Publisher: American Physical Society (APS)
Date: 12-03-2010
Publisher: Springer Science and Business Media LLC
Date: 09-01-2011
DOI: 10.1038/NMAT2931
Abstract: Phase-change optical memories are based on the astonishingly rapid nanosecond-scale crystallization of nanosized amorphous 'marks' in a polycrystalline layer. Models of crystallization exist for the commercially used phase-change alloy Ge(2)Sb(2)Te(5) (GST), but not for the equally important class of Sb-Te-based alloys. We have combined X-ray diffraction, extended X-ray absorption fine structure and hard X-ray photoelectron spectroscopy experiments with density functional simulations to determine the crystalline and amorphous structures of Ag(3.5)In(3.8)Sb(75.0)Te(17.7) (AIST) and how they differ from GST. The structure of amorphous (a-) AIST shows a range of atomic ring sizes, whereas a-GST shows mainly small rings and cavities. The local environment of Sb in both forms of AIST is a distorted 3+3 octahedron. These structures suggest a bond-interchange model, where a sequence of small displacements of Sb atoms accompanied by interchanges of short and long bonds is the origin of the rapid crystallization of a-AIST. It differs profoundly from crystallization in a-GST.
Publisher: American Physical Society (APS)
Date: 07-07-2009
Publisher: American Physical Society (APS)
Date: 06-01-2010
Publisher: Trans Tech Publications, Ltd.
Date: 04-2018
DOI: 10.4028/WWW.SCIENTIFIC.NET/SSP.273.101
Abstract: Liquid metal structure of Sn-Cu alloys studied by synchrotron high energy X-ray diffraction have been performed to investigate the effect of the trace elements Ni and Al. It has been demonstrated that trace Ni and Al additions are able to alter the liquid Sn-4wt%Cu structure. The refinement of the primary Cu 6 Sn 5 phase after trace Al additions is proposed to be caused by the consumption of Cu atoms involved in a AlCu chemical ordering and an associated change in the undercooling for Cu 6 Sn 5 nucleation.
Publisher: American Scientific Publishers
Date: 04-2011
Abstract: We report on structural characterization of sapphire photomodified by voids of sub-wavelength diameter surrounded by amorphised regions formed after exposure by tightly-focused femtosecond laser pulses of 800 nm wavelength and 150 fs duration at the single and double-pulse irradiation inside crystalline sapphire. Regrowth of a crystalline phase near the edge between the amorphous and crystalline phases was observed by transmission electron microscopy (TEM) in the case of double-pulse-irradiated locations. Regions patterned by single-pulse-induced voids inside sapphire were characterized by synchrotron X-ray diffraction (XRD) technique. The XRD patterns indicate presence of an expanded phase of the host crystal. The origin of structural changes observed in TEM and XRD is discussed and is consistent with fast thermal quenching.
Publisher: IOP Publishing
Date: 11-11-2010
Publisher: AIP Publishing
Date: 22-03-2023
DOI: 10.1063/5.0138382
Abstract: A new class of electrolytes have been reported, hybridizing aqueous with non-aqueous solvents, which combines non-flammability and non-toxicity characteristics of aqueous electrolytes with the superior electrochemical stability of non-aqueous systems. Here, we report measurements of the structure of an electrolyte composed of an equal-mass mixture of 21 m LiTFSI-water and 9 m LiTFSI-dimethyl carbonate using high-energy x-ray diffraction and polarized neutron diffraction with isotope substitution. Neutron structure factors from partially and fully deuterated s les exhibit peaks at low scattering vector Q that we ascribe to long-range correlations involving both solvent molecules and TFSI− anions. We compare both sets of measurements with results of molecular dynamics simulations based on a polarizable force field. The structures derived from simulations are generally in agreement with those measured, except that neutron structure factors predicted for two partially deuterated s les show very intense scattering increasing up to the low-Q limit of simulation, indicating a partial segregation between the two solvents not observed in experimental measurements.
No related grants have been discovered for Shinji KOHARA.