Atomistic modeling of step formation and step bunching at the Ge(1Â 0Â 5) surface

We investigate possible step geometries on the rebonded-step reconstructed Ge(1 0 5) surface. We focus our attention on steps oriented along the [0 1 0] direction, which have been shown to play a key role in the pyramid-to-dome transition during Ge growth on Si(0 0 1). Using molecular dynamics simulations based on the Tersoff potential, we evaluate the step formation energy for several alternative structures. The step-bunching process is also analyzed, showing that one monolayer-high steps are likely to group into multistepped structures. Our results provide support for very recent experiments and modeling on the pyramid-to-dome transition in Ge/Si(0 0 1).