Optical and fractal properties of sputter deposited TiO2 films

In this study, TiO2 films were deposited on the glass substrates at different pressures using a DC magnetron sputtering system. The surface topography, fractality, particle size, transparency spectra, and roughness of the deposited films were analyzed through atomic force microscopy in non-contact mode and spectrophotometer (UV–visible) analysis. The Gwyddion open source software was used to analyze the AFM results. The surface morphology, absorption spectra, transparency, and energy band gap of the films were studied through analytical and mathematical relations, including fractal and multifractal dimensions of the films. The pressure influenced the particle size leading to the changes in the surface roughness and fractality of the films. When the working pressure increased above 8 × 10-3 Torr, the nonuniformity in the distribution of surface properties and multifractality increased. Additionally, using optical data and the Tauc’s method, their energy gap was calculated. It was revealed that the TiO2 coatings have a relatively large energy gap of ~ 4 eV, probably due to their small grain size.