Comparison of hydrophilic properties of TiO2 thin films prepared by sol–gel method and reactive magnetron sputtering system

This article reports on preparation, characterization and comparison of TiO2 films prepared by sol–gel method using the titanium isopropoxide sol (TiO2 coating sol 3%) as solvent precursor and reactive magnetron sputtering from substoichiometric TiO2 − x targets of 50 mm in diameter. Dual magnetron supplied by dc bipolar pulsed power source was used for reactive magnetron sputtering. Depositions were performed on unheated glass substrates. Comparison of photocatalytic properties was based on measurements of hydrophilicity, i.e. evaluation of water contact angle on the film surface after UV irradiation. It is shown, that TiO2 films prepared by the sol–gel method exhibited higher hydrophilicity in the as-deposited state but has significant deterioration of hydrophilicity during aging, compared to TiO2 films prepared by magnetron sputtering. To explain this effect AFM, SEM and high resolution XPS measurements were performed. It is shown that the deterioration of hydrophilicity of sol–gel TiO2 films can be suppressed if as-deposited films are exposed to the plasma of microwave oxygen discharge.