Dislocation nucleation from a sharp corner in silicon

Abstract

By combining molecular dynamics simulation with reaction pathway sampling, we have observed the nucleation of a three-dimensional dislocation loop from a sharp corner in silicon and investigated the shear stress dependence of the activation energy and saddle-point configuration. The nucleated shuffle-set half-loop consisted of two 60° segments and one screw segment, each lying along a Peierls valley. The half-hexagonal shape is in good agreement with experiments at low temperature. Under high stress (90%–95% of athermal shear stress), the dislocation embryo is far from perfect, with half-size Burgers vector (about 0.2 nm) and a 0.4–0.7 nm radius forming a diffuse core region. A consequence is that the Rice–Thompson theory gives incorrect predictions regarding the activation energy and saddle-point configuration. With decreasing applied stress (less than 70%), the embryo approaches that of a perfect dislocation.