Growth of WO3 crystals from W-Ti-O thin films

The nucleation and growth of WO3 single crystals induced by annealing W-Ti- O thin films deposited onto Al2O3 substrates has been studied by micro-Rama n spectroscopy. Amorphous W-Ti-O layers have been obtained from RF sputteri ng W-Ti alloy targets in a reactive atmosphere. Annealing of these layers y ielded several WO3 phases depending on the annealing temperature, Ti conten t, and duration of the heat treatment. Monoclinic gamma-WO3 crystallites we re found dispersed onto the layer surface, while in the Ti-rich layer templ ating the Al2O3 substrate higher symmetry WO3 phases have been identified. (C) 1999 Elsevier Science B.V. All rights reserved. PACS: 78.30; 68.55.