Strained island formation in heteroepitaxy

Abstract

Morphological evolution of strained heteroepitaxial films is studied using large scale kinetic Monte Carlo simulations in 1+1 dimensions. Films and substrates are modeled by square lattices of balls and springs representing atoms and elastic interactions respectively. We simulate surface diffusion using an activated hopping algorithm with the hopping rate of each surface atom followed from the coordination number and the strain energy. The repeated calculations of the strain energy is the most computationally intensive part of the simulation. We handle this efficiently using a novel Green's function technique closely related to the boundary integral method. Simulations of the morphological evolution during deposition or annealing are conducted. We observe formation of islands in both cases under a wide range of conditions. The resulting morphology resembles those of Si1-xGex films on Si(001) substrates at low misfits.