1998 Fiscal Year Final Research Report Summary
Growth of single crystalline films of bismuth based oxide superconductors by the liquid phase epitaxy method
| Project/Area Number |
09650004
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Applied materials science/Crystal engineering
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| Research Institution | Tohoku University |
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Principal Investigator |
MIYASHITA Satoru Institute for Materials Research, Tohoku University, Research Associate, 金属材料研究所, 助手 (00219776)
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| Co-Investigator(Kenkyū-buntansha) |
SAZAKI Gen Institute for Materials Research, Tohoku University, Research Associate, 金属材料研究所, 助手 (60261509)
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| Project Period (FY) |
1997 – 1998
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| Keywords | oxide superconductors / liquid phase epitaxy / film crystal / temperature gradient method / bismuth / flux growth / single crystal / substrate |
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| Research Abstract |
Growth conditions of Bi2212 superconducting films on the substrate crystal by the liquid phase epitaxial growth method using KCl as a solvent were investigated, In the case of the starting composition of Bi : Sr : Ca : Cu=2 : 2 : 1 : 2, the best growth temperature ranged from 840 to 870ﾟC.Under this condition, only the 2212 phase film grew on the substrate. In the early stage, the growth mechanism was the island growth and the changed to the continuous film growth mode. When islands met on the substrate, large steps occurred and this made film flattness poor. When we used the LaAlO3(1 10) substrate, however, grown 2201 films showed atomically flat area extending few micrometers square. When we used the NdGaO_3 * (001) substrate, nearly twin free film was obtained.
Dessolution and solidification process of the oxide system of Bi-Sr-Ca-Cu-O was in situ observed with high temperature optical microscopy. We could determined the primary crystallization field (rough region of temperature and composition where the crystals grow as the first solid) for the self flux growth of the Bi based oxide superconductors system. This region we determined contained much bismuth than those ever reported. Traveling solvent floating zone method was applied on the basis of the knowledge of the primary crystallization field. To obtain single crystals thick in the crystallographic c-axis direction, the control of the nucleation by such as seeding was found to be needed. Using the seed crystal, we succeeded in continuous growth from the seed crystal and this indicated that the primary crystallization field we determined was reliable and useful. Next subject on the primary crystallization field is to clearly separate the 2212 phase and the 2201 phase region. We tried the liquid phase epitaxial method using the self flux, to fail. Corrosion of the substrates by the flux enabled us to obtaine the single film crystal. Further study is needed.
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