13 - Surface Morphologies Obtained by Ge Deposition on Bare and Oxidized Silicon Surfaces at Different Temperatures

Abstract

The surface morphology of Ge layers grown over a wide temperature range by Ge deposition on Si(001) and Si(111) surfaces, either bare or covered with ultrathin SiO2 films, is studied with scanning tunneling and electron microscopy. Since the SiO2 film is partly decomposed at temperatures above 430°C, this produces the appearance of bare Si nanoareas which serve for epitaxial Ge island nucleation and growth with respect to the Si substrate. It is essential that the SiO2 film residuals prevent Ge–Si intermixing, allowing pure Ge islands to form. The shapes of such islands are also different from the islands grown on bare surfaces, which contain a significant amount of Si due to strain-induced Si–Ge intermixing. The growth of islands at high temperatures reveals that Si–Ge intermixing cardinally affects not only the island’s chemical composition, but also their shape and distribution over the surface, providing islands ordering on Si(100) or nanowire formation on Si(111). These new surface morphologies may lead to Si−Ge nanostructure fabrication with modified optoelectronic characteristics.