Layers of Si crystals grown on SiO2 surfaces are investigated by scanning tunneling and atomic force microscopy. The deposition of an array of Ge islands on SiO2 surfaces prior to Si growth is found to significantly decrease the concentration of Si crystals and make them more uniform in size. The Si crystals grown at temperatures from 430 to 550 degrees C have a rounded shape of the growing surface. This indicates the presence of a high concentration of threading dislocations and that is confirmed by the observation of dislocation-related photoluminescence in the 1.5 mu m region. Layers of Si crystals grown on SiO2 are of interest for the fabrication of optical resonant structures for the near-infrared region. (C) 2012 Elsevier B. V. All rights reserved.