Electronic Transitions and Dispersion Parameters of Annealed TiO_2 Films Prepared by Vacuum Evaporation Technique

摘要

Titanium dioxide (TiO_2) thin films were successfully grown on glass substrates using vacuum evaporation technique. Optical measurements were studied by UV-VIS technique in the wavelength ranges 300-900 nm. The optical properties and dispersion parameters of the films have been studied as a function of annealing temperature, results show that the annealing temperature has a significant effect on the transparency of the thin films. The optical energy gap decreased from 3.25 to 2.95 eV as the annealing temperature increases to 250 ℃. The density of localized states increased by this process and causes an expanding in the Urbach tail and consequently decreases the energy gap. The changes in dispersion parameters and Urbach tails were investigated. The single-oscillator parameters have been reported.