Analysis of the growth dependences of silicon-on-sapphire heteroepitaxy

The formation of nanoislands of two forms (dome-shaped and a truncated dome) is experimentally found during the initial stage of silicon-on-sapphire heteroepitaxy. Atomic-resolution images of the silicon islands on sapphire are obtained by transmission electron microscopy. A model is proposed to explain the instability of the shape of islands and its transition from isotropic to anisotropic and to describe the evolution of average island sizes during growth. It is shown that the height dependence of the island diameter is approximately linear; however, for large island sizes there is a significant discrepancy with the experimental data due to island coalescence, which is disregarded in the model.