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Huang, X. S.*; Ono, Masao; Ueno, Hideto*; Iguchi, Yusuke*; Tomita, Takeshi; Okayasu, Satoru; Mashimo, Tsutomu
Journal of Applied Physics, 101(11), p.113502_1 - 113502_5, 2007/06
Times Cited Count：25 Percentile：66.75(Physics, Applied)A large linearly graded structure on atomic-scale up to 88 at%/mm with oriented grown crystals was formed in selenium-tellurium (Se-Te) semiconductor using a strong gravitational field of 1 million G level at 260 
C. The lattice constants and the binding energies of Se and Te 3
electrons continuously changed along the direction of gravity accordingly, which indicated the formation of the graded band gap structure. The grown crystals showed the crystalline orientation with c-axis of hexagonal structure roughly perpendicular to the direction of gravity. It was found that the diffusion coefficient of sedimentation was larger than that of normal diffusion by more than 100 times, which suggested a different diffusion mechanism from the normal vacancy mechanism.
Ono, Masao; Kinoshita, Takahiro*; Ueno, Hideto*; Huang, X.*; Osakabe, Toyotaka; Mashimo, Tsutomu
Materials Transactions, 46(2), p.219 - 224, 2005/02
Times Cited Count：8 Percentile：54.95(Materials Science, Multidisciplinary)Ultracentrifuge experiments were performed on the In-Pb system to study the sedimentation of atoms and phase equilibrium. After the experiments, the graded structures were obtained. Pb-rich phase (f.c.c) and In-rich phase (tetragonal) appeared at the strong- and weak-gravitational field sides of the sample, respectively, from starting state of 
-phase. And, the continuous changes in lattice parameters were observed in each phase. These observation results showed that the graded structure was continuous in atomic scale, and was formed by the sedimentation of atoms. Composition profiles of the centrifuged samples for 31.3 h, 60 h and 150 h showed that the composition change reached the steady state within 60 hours. The diffusion coefficient for sedimentation was estimated to be about 8 times larger than that for usual diffusion by the simulation. The result indicated that the diffusion mechanism of the sedimentation was different from the conventional ones.
Ono, Masao; Huang, X.*; Kinoshita, Takahiro*; Ueno, Hideto*; Osakabe, Toyotaka; Mashimo, Tsutomu
Defect and Diffusion Forum, 237-240(2), p.1101 - 1104, 2005/00
Ultra-strong gravitational field can induce sedimentation of even atoms in condensed matter. We had realized sedimentation of substitutional solute atoms in some miscible alloys. How about in the other alloys? So, In this study, the ultra-centrifuge experiments were performed on an intermetallic compound of Bi-Pb system (Bi
Pb
) by changing time duration of experiment time (experimental conditions; maximum centrifugal force: 1.0
10
g level, temperature: 130-150 C, duration: 30-150h, state: solid). Composition changes were observed in the centrifuged samples. And, it was found that the Bi phase appeared from starting state of BiPb around the weak gravitational field region of the sample. These results showed that sedimentation of substitutional solute atoms occurred, and induced the structure change in intermetallic compounds.
