Atomic-scale modeling of next-layer nucleation and step flow at the Ge(105) rebonded-step surface.

Based on ab initio calculations, we propose an atomic-scale path leading to the growth of a new layer on the rebonded-step reconstructed Ge(105) surface. We show that the nucleation of (001)-like dimers triggers the formation of low-energy adtrimers within the surface unit cell. The presence of adjacent trimers and the arrival of a further adatom initiate a fast kinetic process, allowing the perfect rebonded-step structure to be rebuilt. After repeating some of the calculations under compressive-strain conditions, we discuss position-dependent nucleation in (105) Ge pyramid on Si(001), finding solid theoretical justification for the experimentally observed preferential nucleation at the top of Ge islands, followed by fast step flow. © 2007 The American Physical Society.