Self-cleaning and antifogging effects of TiO2 films prepared by radio frequency magnetron sputtering

Abstract

The article reports on the correlation between the structure, the surface morphology, and the photocatalytic behavior of transparent TiO2 films prepared at different total pressures and oxygen partial pressures. The reactive deposition process was conducted in a mixture of Ar and O2 on unheated glass substrate using a rf magnetron sputtering system. The film structure and the surface morphology were investigated by x-ray diffraction and scanning electron microscopy, respectively. The photocatalytic behavior was studied by the measurement of the decomposition of methylene blue and the reduction of the contact angle between water and TiO2 under ultraviolet irradiation. The experiments showed that the photocatalytic properties accompany the changes in the structure and the surface morphology. The phase conversion from the rutile to the anatase TiO2 film leads to an increase in the photocatalytic activity. The rutile films prepared at lower total pressures are characterized by a very low decomposition efficiency and a contact angle about 42° after irradiation. On the contrary, the anatase films with the best photocatalytic behavior are prepared at higher total pressures (>1.50 Pa) and characterized by a high decomposition efficiency, a contact angle about 10° after irradiation, and a good stability in darkness. Such anatase films possess the surface morphology of a lower density, a higher surface roughness, and a larger surface area. Moreover, the TiO2 films deposited in the transition sputtering mode showed a lower decomposition efficiency. The TiO2 films prepared in the reactive mode at the same total pressure exhibited the similar photocatalytic behavior with small variations only.