Surface morphology of Ge layers epitaxially grown on bare and oxidized Si(001) and Si(111) substrates

The surface morphology of Ge layers grown by Ge deposition on the Si(001) and Si(111) surfaces covered with ultrathin SiO2 films is studied with scanning tunneling microscopy. It is essentially different from that obtained by Ge deposition on the bare Si surfaces, which are performed in similar conditions for comparison. The SiO2 film is partly decomposed at temperatures above 430 degrees C, leading to the formation of bare Si nanoareas which serve for the epitaxial Ge island nucleation and growth with respect to the Si substrate. At the same time, we found that the SiO2 film residuals prevent the Ge-Si intermixing providing pure Ge islands formation. They appear to be different in shape from the islands grown on the bare surfaces, which contain a significant amount of Si due to the strain-induced Ge-Si intermixing. The possibility of pure Ge islands formation may lead to the Ge/Si nanostructures fabrication with modified optoelectronic characteristics. (C) 2014 Elsevier B.V. All rights reserved.