Optical studies on sol-gel derived titanium dioxide films

Optical absorption A(λ) and transmission T(λ) spectra for normal incidence have been obtained within the wavelength (λ) range 300-900 nm for titanium dioxide (TiO₂) films in anatase form prepared by the sol-gel method. The dispersion relation for refractive indices is in agreement with the oscillator model. The refractive index is found to be independent of thickness. Above the absorption tail, optical absorption is believed to be due to nondirect electronic processes involving no transitions between localized states in a single layer thick TiO₂ film. For a multilayered film, transitions between localized states are probable as equal as those between all other states.