Optical properties of SrTiO₃ thin films deposited by radio-frequency magnetron sputtering at various substrate temperatures

SrTiO₃ thin films were deposited on vitreous silica substrates at various substrate temperatures (300-700°C) by rf magnetron sputtering technique. The transition from amorphous phase to polycrystalline phase for the films occurred at the substrate temperatures of 300-400°C. Their optical properties were investigated by transmittance measurements. The fitting method was used to calculate the refractive index and the film thickness from the transparent region of the transmittance spectra. The refractive index increased and the film thickness decreased with the substrate temperatures increasing. The dispersion of the refractive index was studied by considering a single electronic oscillator model. The band gaps of the films were estimated from Tauc's law and showed a decreasing tendency to that of the bulk SrTiO ₃ with the substrate temperatures increasing. These results provide some useful references for the potential application of SrTiO₃ films in integrated optics devices.