Dislocation Nucleation from a Surface CUSP

Abstract

ABSTRACTTheoretical and experimental studies have suggested that surface roughness may significantly enhance the nucleation of misfit dislocations in a strained heteroepitaxial film, especially in view of a stress-induced roughening instability which tends to form cusp-like stress singularities along the film surface. In this paper, the process of dislocation nucleation is perceived as a single dislocation emerging from a gradually sharpening surface groove. An analysis similar to the Rice-Thomson model for dislocation nucleation from a crack tip is carried out to determine the nucleation condition in terms of the depth and curvature of the surface groove. Specific applications are made to Si1−xGex alloy films on Si (100) substrates.