Formation, ripening, and stability of epitaxially strained island arrays

We study the formation and evolution of coherent islands on lattice-mismatched epitaxially strained films using two-dimensional evolution simulations. Faceted islands form in films with anisotropic surface tension. Under annealing, these islands ripen until a stable array is formed. We show that the presence of a cusp in the surface tension is essential for reproducing the experimentally observed characteristics of the stable island array. It is also shown that a single cusp in the surface energy is sufficient in order to explain the island-shape transition and associated bimodal island-size distribution which occurs in growth experiments. In films with isotropic surface tension we observe and explain a new mode of growth in which a stable wavy surface is formed.