Influence of film thickness on optical and morphological properties of TiO2 thin films

Titanium dioxide (TiO2) thin films of different thicknesses were prepared on a glass substrate by using the electron beam evaporation method. The film thickness was estimated using multiple-beam Fizeau fringes in reflection. The optical properties and surface morphology of the films were studied by using an ultraviolet-visible double-beam spectrophotometer and an atomic force microscope (AFM), respectively. The spectral transmittances of the deposited samples were measured in the range 300-800 nm. It was revealed that the decrease in film thickness enhanced the transmittance. Optical bandgaps were calculated from Tauc's plots for different thicknesses and were found to increase with increasing film thickness. The dependence of the absorption coefficient on the wavelength as well as the optical density and extinction coefficient was found to be affected by film thickness. AFM measurements indicated that the average roughness and root-mean-square roughness increased with increasing film thickness.