Formation of pyramids and mounds in molecular beam epitaxy

One of the generic scenarios in molecular beam epitaxy is the growth of three-dimensional structures such as mounds and pyramids. These structures are a nonequilibrium effect thought to be due to a combination of the microscopic Ehrlich-Schwoebel barriers and the breaking of detailed balance by the deposition process. We propose and investigate by computer simulation a simple microscopic model that displays (i) slope selection, (ii) pyramid and moundlike structures, and (iii) coarsening. The characteristic length scale of our three-dimensional features grows as $R\left(t\right)\mathrm{}\sim t^n$ with $n$ between 0.17 and 0.26. We discuss these results in the light of recent experiments and continuum models of molecular beam epitaxy.