Evolution with temperature of a single sol–gel TIO 2 layer on sapphire (α-Al 2O 3) (0 0 0 1)

Abstract

TiO 2 sol–gel layer has been deposited on single crystal sapphire (0 0 0 1) substrate. Evolution of the layer microstructure with the thermal treatment in the range 100–1100 °C has been studied using X-ray diffraction and X-ray reflectometry. TiO 2 layer density first increases with temperature up to 800 °C and then decreases with the appearance of a high roughness finally leading to anatase islands formation. The single crystal nature of the substrate seems to contribute to hinder the transformation of the anatase phase into the rutile phase and to induce a preferred orientation of the TiO 2 islands.