Effect of Annealing Treatment on Optical Properties of TiO2 Thin Films Prepared by Rapid Thermal Oxidation

TiO2 thin films have been prepared by rapid thermal oxidation of Ti thin films grown on glass substrates using a hot plate at temperature 450ºC for 30 sec . The films were then annealed at 300,500ºC in air for a period of 1 hour to study The effects of annealing temperature on optical properties of TiO2 . The optical constants were characterized using the transmission spectra of the films obtained by UV-VIS-IR spectrophotometer. It was observed that TiO2 films exhibited high visible transmittance and transmittance increased with increasing of annealing temperature. The extinction coefficient was nearly zero in the visible range, both absorption coefficint and extinction coefficient decrease with increasing of annealing temperature.The refractive index of the films was found from (1.8-2.5) at 340 nm, and increased with increasing of annealing emperature. The optical band gaps were evaluated through Tauc model. The allowed direct band gap was found to increase from 3.70 eV to 3.78 eV, while allowed indirect band gap increase from 3.20 eV to 3.40 eV with increasing of annealing temperature