Kinetic Monte Carlo simulation of shape transition of strained quantum dots

Abstract

The pyramid-to-dome transition in Ge᙮Si₁₋᙮ on Si(100) initiated by step formation on pyramidal quantum dots is atomistically simulated using a multistate lattice model in two-dimensions incorporating effective surface reconstructions. Under quasiequilibrium growth conditions associated with low deposition rates, the transition occurs at island size nᴄ following (see article file for details of the abstract) independent of temperature and deposition rate. The shape transition is found to be an activated process. Results are explained by a theory based on simple forms of facet energies and elastic energies estimated using a shallow island approximation. An asymptotic scaling relation (see article file for details of the abstract) for x→0 applicable to d=2 or 3 dimensions is derived. The shape transition energy barrier can be dominated by the interface energy between steep and shallow facets.