Effect of microstructure and crystallinity on the photocatalytic activity of TiO₂thin films deposited by dc magnetron sputtering

Abstract

TiO2 thin films were deposited by dc magnetron sputtering from sub-stoichiometric TiO2−x targets. The as deposited films were XRD amorphous and their microstructure was varied by changing the Ar-pressure and the applied dc power during sputtering. An anneal treatment at 673 K/1 h in air resulted in the crystallization of a preferentially oriented anatase phase, the degree of which depended on the deposition conditions. The microstructure, optical and photocatalytic properties of the thin films were investigated using SEM, UV–VIS spectroscopy and a custom made photocatalytic test reactor, respectively. The thin film density was estimated from their refractive index. Density and crystallinity were the most important factors determining the photocatalytic activity of the thin films.