PNNL

Abstract

Molecular dynamics (MD) has been employed to study the disordering and amorphization processes in SiC irradiated with Si and Au ions. The 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. No evidence of amorphization is found at the end of the cascades created by Si recoils. However, the structure analysis indicates that the large disordered domains generated by Au recoils can be defined as an amorphous cluster lacking long range order. The driving force for amorphization in this materials is due to the local accumulation of Frenkel pairs and antisite defects. These results are in good agreement with experimental evidences, i.e. the observed higher disordering rate and the residual disorder after annealing for irradiation with Au2+ are associated with a higher probability for the in-cascade amorphization or formation of large disordered cluster.