Identifying He- and H-vacancy complexes in 3C-SiC by temperature-dependent positron annihilation lifetime calculations

Abstract

The effect of temperatures ranging from 0 K to 1000 K on the positron lifetime of He- or H-vacancy complexes in 3C-SiC are studied using first-principles calculations. We observed a steady decrease in the formation energy of H-vacancy complexes upon additional H introduction, in contrast to the variation tendency of formation energies seen in He-vacancy complexes. The intrinsic vacancies ($V_{\mathrm{Si}}$, $V_C$, and $V_{\mathrm{Si}+C}$) exhibit different decrease in positron lifetime with the addition of He or H atoms, with the effect of He being more pronounced. Moreover, $V_C$ and its impurity-vacancy complexes are almost incapable of trapping delocalized positrons, with positron lifetimes close to those of the bulk. Positron lifetime calculations for the complexes show no significant temperature dependence from 0 K to 1000 K, except in the case of $V_C$. The above results are interpreted by analysis of electron density, positron density, positron ground-state energy, and positron trapping energy analysis. The results provide a reference for future in-situ temperature-dependent positron lifetime experiments on impurity-vacancy complexes in 3C-SiC.