Optical constants of heat-treated TiO2 thin films

RF sputtering technique has been used to obtain titanium dioxide thin films onto unheated glass substrates. X-ray diffraction (XRD) patterns reveal an amorphous structure for the as-deposited films and a polycrystalline structure, having mixed anatase/rutile phases, for films heat treated at temperatures higher than 360 °C. The heat treatment also induces a change in the surface morphology of TiO2 thin films. The optical constants of TiO2 thin films have been ellipsometrically obtained, during annealing, in the temperature range 50–400 °C. A sudden rise of the optical constants has been observed around 360 °C, explained by the transition phase from amorphous to polycrystalline structure. Heat treating the glass substrate in the same temperature range, no significant differences of the optical constants values from those obtained at room temperature were observed.