Recovery of close Frenkel pairs produced by low energy recoils in SiC

Abstract

Simulations of displacement cascades in silicon carbide (SiC) indicate that most defects created are point defects, where interstitials are displaced only a small distance from the nearest vacancies. Of the interstitial defects produced in SiC, about 40% survive as freely migrating interstitials that can contribute to microstructural evolution during irradiation of SiC. The stable defect configurations in this study were created with low-energy recoils using molecular dynamics (MD) simulation. These stable Frenkel pairs have been annealed at different temperatures, using MD methods, to determine the time required for interstitials to recombine with vacancies. The MD data have been analyzed using an Arrhenius relation, and the activation energies for defect recombination processes range from 0.22 to 1.6 eV for C Frenkel pairs and from 0.28 to 0.9 eV for Si Frenkel pairs. These low activation energies for spontaneous recovery of Frenkel pairs in SiC are qualitatively consistent with the recovery processes observed experimentally on both the Si and C sublattices below room temperature. Based on the data analysis, the spontaneous recombination distance is estimated to be 0.66 and 0.70 ao for the C and Si sublattices, respectively.