Positron annihilation investigation of vacancies in as-grown and electron irradiated dia onds
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Date
2000-05-01T00:00:00Z
Authors
Pu, Anle
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Abstract
Vacancy-type defects in the four main types of diamond (Ia, Ib, IIa and IIb) were investigated using positron lifetime, Doppler broadening and optical absorption spectroscopies. In unirradiated samples vacancy clusters were found in all types, synthetic as well as natural. These clusters are situated in highly defected regions, rather than homogeneously distributed, and their concentration varies significantly from sample to sample. For synthetic Ib diamonds vacancy clusters were investigated as a function of nitrogen content. We have developed a simplified model for the trapping of positrons by ' negatively' charged vacancies. By solving the differential equations pertaining to the population of positron states, expressions for the experimentally observable positron parameters (lifetimes, their intensities and the Doppler broadening parameter S) were obtained. (Abstract shortened by UMI.)