PNNL

Abstract

Molecular dynamics (MD) simulations, experimental studies and a theoretical model have been combined in an investigation of the disordering and amorphization processes in SiC irradiated with Si and Au ions. In MD simulations, large disordered domains, consisting of interstitials and antisite defects, are created in the cascades produced by Au primary knock-on atoms (PKAs); whereas Si PKAs generate only small interstitial clusters, with most defects being single interstitials and vacancies distributed over a large region. The data for cluster spectrum obtained from MD simulations have been used to calculate the relative cross sections for in-cascade amorphization (or clustering)and in-cascade defect-stimulated amorphization. The ratio of these cross sections for Si and Au is in excellent agreement with thhose derived from the experimental data based from a fit of the direct-impact/defect-stimulated model. This suggests that the observed higher disordering rate and the residual disorder after thermal annealing at 300 K for irradiation with Au2+ are associated with a higher probability for the in-cascade amorphization or large disordered cluster formation. The observed different behavior for the accumulation and recovery of disorder in SiC irradiated by Si and Au ions is quantatatively consistent the present MD simulations and direct-impact/defect-stimulated model.