Effect of sputtering parameters on the self-cleaning properties of amorphous titanium dioxide thin films

The aim of this work was to assess the effect of the direct current magnetron sputtering parameters on the photocatalytic activity and photoinduced wettability of amorphous TiO₂ films. TiO₂ films were deposited on glass using the direct current magnetron sputtering technique, without heating, at different total working pressures. Qualitative analysis using in situ X-ray photoelectron spectroscopy confirmed the TiO₂ stoichiometry of the deposited films. Surface structure was studied as a function of working pressure using scanning electron microscopy. The hydrophilicity of the TiO₂ surfaces was investigated macroscopically using measurements of the water contact angle. A threshold working pressure was observed, with a strong dependence on the film thickness. A super hydrophilic surface was observed after less than 1 h of UV irradiation. The photocatalytic activity of the films was evaluated under UV light through the degradation of methylene blue (\(\lambda_{\hbox{max} } \approx 660\;{\text{nm}}\)). The effect of UV irradiation on the photocatalytic activity was rapid, strong, and dependent on film thickness and total working pressure. Fifty percent of organic compounds were photodegraded by films with a thickness of 60 nm deposited at 10 mTorr.