Investigation on microstructure and optical properties of titanium dioxide coatings annealed at various temperature
TiO 2 coatings were prepared on fused silica with conventional electron beam evaporation deposition. After TiO 2 thin films were annealed at different temperatures for 4 h, several properties were investigated by X-ray diffraction (XRD), spectrometer, photoelectron spectroscopy (XPS) and AFM. It was found that with the annealing temperature increasing, the transmittance of TiO 2 coatings decreased, and the cutoff wavelength shifted to long wavelength in near ultraviolet band. Especially, when coatings were annealed at high temperature, the optical loss is very serious, which can be attributed to the scattering and the absorption of TiO 2 coatings. XRD patterns revealed that only anatase phase was observed in TiO 2 coatings regardless of the different annealing temperatures. XPS results indicated that the fine chemical shift of TiO 2 2p 1/2 should be attributed to existence of oxygen vacancies around Ti +4 ion. The investigation on surface morphology by AFM showed that the RMS of titania thin films gradually increases from less than 0.40 nm to 5.03 nm and it should be ascribed to the growth of titanium dioxide grain size with the increase of annealing temperature.