First-principles study of diffusion of zinc vacancies and interstitials in ZnO

A comprehensive investigation of zinc vacancy and interstitial diffusion in ZnO has been performed using ab initio   total energy calculations with both the local density approximation (LDA) and the generalized gradient approximation (GGA). Zinc interstitial is found to diffuse efficiently with a small barrier, 0.3–0.5 eV. Therein, the diffusion perpendicular to cc axis tends to occur via an interstitial mechanism, and the diffusion parallel to cc axis tends to occur via a kick-out mechanism. The diffusion of the zinc vacancy is found to be isotropic, and the migration barrier of the zinc vacancy is about 1.0 eV. Based on our results, zinc vacancies are responsible for the self-diffusion of zinc for nn-type ZnO.