Effect of Sb on Si/Si and Ge/Si growth process

In this paper, we investigate the surfactant effect of Sb on the growth of Ge on Si(1 1 1) and on Si(1 0 0). We show that Sb has mainly two effects: first it delays the 2D–3D growth mode transition and consequently permits to produce thicker flat Ge layers; second Sb promotes the layer by layer 2D nucleation growth mode. The latter effect can be used to considerably reduce the lateral size of Ge islands at 550 °C on both Si(1 1 1) and Si(0 0 1). In order to understand the fundamental role of Sb on the growth processes, we have determined the microstructure and the growth mode of Ge layers deposited on Si and on one monolayer Sb/Si surfaces by atomic force microscopy and reflection high-energy electron diffraction (RHEED). We show that the growth mode changes induced by Sb at 350 and 550 °C (thicker 2D wetting layer and smaller islands, respectively) are explained by the conjugated effects of thermodynamics (decrease of the surface energy) and of kinetics (decrease the surface diffusion length) induced by Sb. We finally suggest that partial desorption of Sb is responsible for the formation of islands at 550 °C.