Influence of annealing temperature on the properties of titanium oxide thin film

The influence of annealing temperature on the micro-structure, surface morphology and optical property of TiO₂ thin films prepared by mid-frequency ac magnetron sputtering technique has been studied. The micro-structure and surface morphology were examined by X-ray diffractometer (XRD) and atomic force microscopy (AFM). The transmittance and reflectance spectra of TiO₂ thin films on fused silica substrate were measured by spectrophotometer. The reflective indices and extinction coefficients of TiO₂ films were calculated by envelope method and experimental expression, respectively. The results show that the TiO₂ thin film sputtered at room temperature is amorphous. After annealing under lower temperature (=700 °C), anatase phase appeared in TiO₂ thin film. After annealing under higher temperature (=900 °C), the structure of TiO₂ thin film changed into rutile completely; the TiO₂ grains changed from column to nubbly. The refractive index of TiO₂ thin film increases with annealing temperature and the extinction coefficient decreases a little during the lower temperature anneal. The TiO₂ thin film annealed at 500 °C has the best optical property.