An atomistic picture of the diffusion of two vacancies forming a di-vacancy in si

Abstract

A method is proposed to calculate the formation of a point defect pair in Si based on an atomistic picture. As an illustration, the capturing of a vacancy (V) by another V forming a di-vacancy is described semi-quantitatively. It is shown that in Si, the number of most likely diffusion paths of two vacancies V to form a di-vacancy is limited. The energetically most favorable diffusion paths are the twelve zigzag Si chains surrounding the V along the 110 directions. Systematically calculating all of the irreducible configurations of two vacancies, each with its weight (=total number of each possible configuration), enables determining all possible V diffusion paths with their relative weights. This obtained picture is different from diffusion in the continuum model, which does not take into account the anisotropy of covalent bonds in the diamond lattice. The proposed approach is a first step towards the calculation of the effective "capture cross-section" for the formation of point defect pairs that can be used in continuum models.