1997 Fiscal Year Final Research Report Summary
Study of Vacancy clusters and their electronic structure using positrons
| Project/Area Number |
08650762
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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 |
Physical properties of metals
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| Research Institution | Tohoku University |
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Principal Investigator |
HASEGAWA Masayuki Institute for Materials Research Tohoku University, Professor, 金属材料研究所, 教授 (80005975)
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| Co-Investigator(Kenkyū-buntansha) |
TANG Zheng Institute for Materials Research Tohoku University, Research Associate, 金属材料研究所, 助手 (80271972)
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| Project Period (FY) |
1996 – 1997
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| Keywords | Positron Annihilation / Silicon / Vacancies / First-Principles Calculation / 2D-ACAR / Silicon Carbide |
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| Research Abstract |
The positron annihilation technique has emerged as a powerful tool to study vacancy-type defects in metals and semiconductors. Positrons are sensitively trapped at defects and are annihilated there with the surrounding electrons, conveying significant information on the local electronic environment around the defect site with the emitted two gamma photons. In this field, positron lifetime and Doppler broadening methods have been emplyed. However, a more sophisticated positron annihilation technique "two dimensinal angular correlation of annihilation (2D-ACAR)"can provide us with more significant information about the defects. In this study, 2D-ACAR experiments have been carried out on Si, SiC and their related materials. Furthermore we have made first-principles calculations for 2D-ACAR spectrum.
Interesting features of 2D-ACAR distribution for singly negative divacancies in Si were studied experimentally and theoretically. Anisotropy of the distribution is successfully detected for a specimen with aligned divacancies and well repreduced by first-principles calculations based on the two-component (positron-electron) density functional theory. The present calculation demonstrates that the anisotropy reflects the characteristic distribution of electrons around the divacancies, indicating that the 2D-ACAR is an effective tool to provide microscopic information on vacancy-type defects. Very useful information has been also obtained for perfect crystals of Si, SiC,diamond and graphite, and vacancies in them.
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