Microstructure of high-pressure-synthesized diamonds under rapid quenching and electron irradiation |
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Authors: | L-W Yin M-S Li Z-G Gong Z-Y Hao |
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Institution: | (1) College of Materials Science and Engineering, Shandong University, Jinan 250061, P.R. China, CN;(2) National Key Laboratory for Superhard Materials, Jilin University, Changchun 130012, P.R. China, CN |
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Abstract: | A type of synthetic diamond single crystal about 0.4–0.5 mm in dimension prepared under high pressure–high temperature (HPHT)
in the presence of a FeNi molten catalyst was quenched from HPHT and irradiated with 300 keV electrons at room temperature.
Transmission electron microscopy was employed to examine the microstructure of the diamond single crystal before and after
electron irradiation. It was found that there exists a large amount of cellular interfaces in the quenched diamond sample,
which indicates the growth condition of the diamond under HPHT. Hexagonal dislocation loops about several tens of nanometers
in dimension were observed in the high-pressure-synthesized diamond single crystal before electron irradiation, which strongly
suggests that a number of vacancies were quenched-in due to rapid quenching from high temperature at the end of diamond synthesis,
and were aggregated in the synthetic diamond to form vacancy disks on the (111) plane, the collapse of such vacancy disks
forming vacancy-type dislocation loops. After electron irradiation, it was found that defect clusters present as interstitial-character
dislocation loops were formed in the electron-irradiated region of the diamond. The interstitial dislocation loops grow with
increase of the irradiation time. The present study, in comparison to previous work on ion implantation on diamond, indicates
that electron irradiation does not induce a phase transformation but produces interstitial dislocation loops due to the migration
of interstitial atoms and vacancies. The result of the study directly indicates that interstitials and vacancies in diamond
are mobile at room temperature under electron irradiation. Nitrogen, as the most important kind of impurity contained in the
HPHT as-grown diamond, probably acts as nucleation of the interstitial loops.
Received: 16 November 2001 / Accepted: 12 June 2002 / Published online: 17 December 2002
RID="*"
ID="*"Corresponding author. E-mail: yinlw@sdu.edu.cn |
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Keywords: | PACS: 61 80 Fe 68 37 Lp 81 05 Uw 61 72 Ji |
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