Coarsening and slope evolution during unstable epitaxial growth

%AB % We present simulations of a solid-on-solid model to characterize the formation and evolution of pyramidlike structuress (mounds) that occur during epitaxial growth. Our model includes a nonthermal short-range mobility upon deposition, and surface diffusion with step-edge barriers to interlayer migration. The average mound size is found to vary according to a power law, ∝(time${)}^{\mathit{n}}$, with the exponent n≊0.19 to 0.26 at later stages of growth. Depending on the model parameters, the slope of the mounds stays approximately constant or grows according to a power law. We observe a competition between coarsening and steepening of the mounds. The surface width (roughness) evolution is determined by the behavior of the mound size and slope. Dependence of the rates of coarsening and steepening of the mounds on the model parameters and growth conditions is studied, and the initial stages of the surface morphology evolution discussed.