1994 Fiscal Year Final Research Report Summary
Study of crystal growth mechanism Utilizing microgravity
| Project/Area Number |
05044081
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| Research Category |
Grant-in-Aid for international Scientific Research
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| Allocation Type | Single-year Grants |
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| Section | Joint Research |
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| Research Institution | University of Tokyo |
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Principal Investigator |
NISHINAGA Tatau University of Tokyo, Faculty of Engineering, Professor, 工学部, 教授 (10023128)
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| Co-Investigator(Kenkyū-buntansha) |
CHEROV A.a. Institute OF Crystallography, Academy of Sciences of Russia, Professor, 結晶学研究所, 教授
DANILEWSKY A.n. Freiburg Univ., Crystallographic Institute, Assistant, 結晶学研究所, 助手
BENZ K.w. Crystallographic Institute, Freiburg Univ., Professor, 結晶学研究所, 教授
TANAKA Masaaki University of Tokyo, Faculty of Engineering, Assoc.Professor, 工学部, 助教授 (30192636)
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| Project Period (FY) |
1993 – 1994
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| Keywords | Crystal growth mechanism / Microgravity / Macrostep / Solution growth / Semiconductor / Spacelab / InP / GaSb |
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| Research Abstract |
Under microgravity since thermal convection is stopped, one can eliminate all kinds of convection in the solution if one avoids free surfaces. In this project, thr crystal growth mechanism in a solution was studied by making use of this ideal condition for the growth. Macrostep is especially studied to find elementary growth process. Firstly, the cross section of space grown InP was investigated by optical microscope and the behavior of macrostep was studied in detail. It was found that macrostep is formed in the beginning of the growth but it disappears when the growth approaches to a steady state. The Inp crystals were grown in Germany side in spacelab D-2 and EURECA mission. The employed growth technique was THM (traveling heater method). In this technique, rather strong temperature gradient was applied at the growth front. It turned out that the temperature gradient and the growth velocity are major factors which govern the creation and annihilation of the macrostep.
Theoretical studies were also made jointly by Japanese and German groups. By solving 3D diffusion equation numerically with a shape boundary condition of macrostep, it was shown that the angle between macrostep terrace and riser decreases with increasing temperature gradient and with decreasing the growth velocity. This means that the macrostep disappears in such conditions.
The macrostep stability was also studied for the solution growth of ADP and KDP at room temperature from water solution by Russian group. It was shown that macrostep appears or disappears depending on the flow direction against the orientation of vicinal surface. This was explained in terms of the non-uniformity of the solute concentration associated with the macrostep. This idea is consistent with the theory developed for the InP macrosteps. It was concluded that the origin of macrostep is the instability of the growing surface caused by the 3D diffusion and non-flat interface.
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