Atomic-scale mechanisms for surfactant-mediated layer-by-layer growth in homoepitaxy are investigated theoretically. Starting with minimal assumptions on relative bond strengths, we demonstrate that four possible mechanisms can be operative in enhancing layered growth: (1) a high density of islands at the initial growth stage of each layer, (2) a reduced activation barrier for atoms to cross steps, (3) incorporation into a growing island, and (4) an effective increase in the migration rate on top of the island. We assess the relative importance of these processes by computer simulations.

• Received 14 October 1993

DOI:https://doi.org/10.1103/PhysRevLett.72.693