Optical properties of TiO ₂ thin film grown on quartz substrate by sol-gel method

TiO ₂ film was deposited on quartz substrate by sol-gel method. X-ray diffraction analysis and Raman scattering measurement indicate that the TiO ₂ film is the pure rutile phase structure. From photoluminescence spectra, it is found that the TiO ₂ film shows a near-infrared luminescence band centered at about 832 nm, and two visible luminescence bands centered at about 426 nm and 524 nm, respectively. The refractive index n, extinct coefficient k, optical band gap EOBG and thickness d of TiO ₂ film were extracted by fitting transmission spectra with the Adachi's dielectric function model and a three-phase layered model. It is found that n value increases and then decreases with increasing wavelength, while k decreases continuously. The thickness of TiO ₂ film is about 297 nm. EOBG value is about 3.72eV and larger than that attained by Tauc's law, which is about 3.28eV.