Mechanisms of dislocation nucleation in strained epitaxial layers

Using molecular static simulations we have studied possible mechanisms of stress relaxation with misfit dislocation nucleation in strained heteroepitaxial layers. Two-dimensional models of atomic systems with Lennard-Jones type potential were considered. Combination of total energy minimization with spherical repulsion and nudged elastic band calculation allowed us to study possible transitions between an initial coherent interface state and a final state with a single dislocation. Different transition paths involving either successive relaxation of layers or concerted sliding along atomic rows have been identified as possible mechanisms with low activation energies. The role of these mechanisms in heteroepitaxial thin film growth and possible implementations in three dimensions are discussed.