Atomistic study of intrinsic defect migration in 3C-SiC

Atomic-scale computer simulations, both molecular dynamics (MD) and the nudged-elastic band methods, have been applied to investigate long-range migration of point defects in cubic SiC (3C-SiC) over the temperature range from 0.36Tₘ0.2em0ex to 0.95Tₘ (melting temperature). The point defect diffusivities, activation energies, and defect correlation factors have been obtained. Stable C split interstitials can migrate via the first- or second-nearest-neighbor sites, but the relative probability for the latter 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 barriers obtained for C and Si interstitials are consistent with the activation energies observed experimentally for two distinct recovery stages in irradiated SiC. Also, energy barriers for C interstitial and vacancy diffusion are in reasonable agreement with ab initio data.