Point-defect recombination efficiency at grain boundaries in irradiated SiC

Abstract

We studied the atomic-scale mechanisms of radiation damage recovery, by molecular dynamics simulations of irradiation cascades in a $\ensuremath{\beta}\text{\ensuremath{-}}\mathrm{Si}\mathrm{C}$ model system, containing one general (001) twist grain boundary in the direction approximately perpendicular to the cascade. The (001) grain boundary has a disordered atomic structure, representative of high-angle, high-energy boundaries in cubic silicon carbide. Compared to the perfect crystal model system, we find a relevant effect of grain boundaries on the annealing of cascade defects, both in terms of localization of defects, which are preferentially concentrated around the grain boundary, and of relative defect recovery efficiency. In general, C interstitials are the prevalent type of defect over the whole range of energies explored. A slight grain boundary expansion is observed, accompanied by a broadening of the central atomic planes.