Atomistic models of dislocation formation at crystal surface ledges in Si1-xGex/Si(100) heteroepitaxial thin films

Abstract

Abstract Mechanisms of defect formation near surface ledges of a diamond cubic crystal subjected to compressive strain parallel to the surface are investigated as precursory processes to dislocation nucleation in Si1-xGex/Si(100) heteroepitaxial thin films under surface diffusion conditions. This study is motivated by our preliminary calculations of dislocation formation at surface ledges in a model crystal characterized by the 6–12 Lennard-Jones interatomic potential, and by our controlled annealing experiments on evolution of a Si1-xGex/Si(100) film from an atomically flat, defect-free, surface morphology to an undulating surface morphology with cusp-like surface features and dislocation formation at the cusp valley. When subjecting such films to high temperature anneals, we observed nucleation and growth of three types of dislocations: the 60° glide dislocations, the 90° Lomer-Cottrell dislocations with stair rod Shockley partials and twinned wedge disclinations with twofold ∑9 coincidence boundaries b...