PNNL

Abstract

Atomic-scale computer simulations, both molecular dynamics (MD) and the nudged-elastic band method, have been applied to investigate long-range migration of point defects in 3C-SiC over the temperature range from 0.36 to 0.95 Tm (melting temperature). A wide set of diffusion characteristics has been obtained, including the self-diffusion coefficient, activation energy and defect correlation factor. Stable C split interstitials can migrate via the first or second neighbor sites, but the relative probability for the later mechanism is very low. Si interstitials migrate directly from one tetrahedral position to another neighboring equivalent position by a kick-in/kick-out process via a split interstitial configuration. Both C and Si vacancies jump to one of their equivalent sites through a direct migration mechanism. The migration energies obtained for C and Si interstitials are consistent with those obtained experimentally for the recovery processes in irradiated SiC. Also, energy barriers for C interstitial and vacancy diffusion are in reasonable agreement with ab initio data.