Tailoring of TiO2 film crystal texture for higher photocatalysis efficiency

Nanocrystalline TiO2 thin films were deposited on borosilicate glass substrates using pulsed DC reactive magnetron sputtering in oxygen rich O-2-Ar gas mixtures. The influence of sputtering power and argon-oxygen gas flow ratio over crystallinity, crystal texture and surface morphology of the films was investigated. Interestingly, there was no correlation between the O/Ti concentration ratio in the films and their indirect band gap values. Based on experimentally observed band gap values and other properties of the films the model of the films consisting of nearly stoichiometric TiO2 crystals with a small fraction of weakly coordinated Ti impurities or amorphous low oxidation state titanium suboxide formations is proposed. Photocatalytic activity of the deposited films was analysed using inorganic markers and strong correlation between photocatalytic efficiency of TiO2 films with the (004) Crystalographic Preffered Orientation parameter was observed.