Influencing surface phenomena by Au diffusion in buffered TiO2-Au thin films: Effects of deposition and annealing processing

Enhanced optical properties of TiO2 thin films can be achieved by doping or coating with metals. Metal-doped TiO2 can reduce electron-hole recombination and increase hydroxyl radical concentration on the surface of TiO2, resulting in increase of the photocatalytic activity. TiO2 and TiO2-Au thin films were obtained by DC magnetron sputtering of Ti target with Ar ions in O2 atmosphere. In the case of Au buffered TiO2 thin films, two different systems were deposited for comparison. Post deposition annealing at 400 °C was carried out in nitrogen atmosphere for 3 h. The structural and optical characteristics of the prepared films were investigated in detail by the combination of high-resolution microscopic and spectroscopic techniques. The photo-degradation rate was measured using Rhodamine B which simulated pollutant. Post deposition annealing resulted in diffusion of Au atoms through the layer as it was revealed by transmission electron microscopy and energy dispersive X-ray spectroscopy. The obtained TiO2 thin films were found to be amorphous after deposition and annealing at 400 °C leads to crystallization of anatase phase. Analysis of the binding energy in the corresponding X-ray photoelectron spectra has confirmed stoichiometry of TiO2 and that concentration of Au on the surface can be controlled by sputtering and annealing conditions, thus changing optical properties by influencing the surface plasmonic nature. All Au doped TiO2 thin films exhibited enhanced wettability and photo-degradation rates when compared to pristine titania films. © 2022 Elsevier B.V.