Grain size reduction on nanostructured TiO2 thin films due to annealing

Abstract

TiO2 thin films have been deposited at 300 °C on quartz substrates by a metal-organic chemical vapor deposition technique. The obtained films have been annealed at different temperatures up to 1100 °C. X-ray diffraction studies show that the obtained films maintain the anatase phase till 800 °C annealing temperature, and the rutile phase appears at 900 °C. Extra unidentified peaks appear at 1000 °C, and 1100 °C. Raman microscopy has been used to identify the obtained films. The obtained spectra show the normal modes of vibrations of the pure and mixed phases. Scanning electron microscopy graphs show grain size shrinkage concurrent to the appearance of the rutile phase. A slight band gap reduction has been calculated from UV-Vis transmittance spectrophotometery measurements. DC conductivity curves show three regions with different activation energies.