The influence of pressure on the structure and the self-cleaning properties of sputter deposited TiO2 layers

TiO2-layers for self-cleaning applications were deposited on glass and silicon wafer by reactive dc-sputtering at various oxygen and argon pressures in the range from 0.18 Pa to 3.0 Pa. With an increasing sputtering pressure the microstructure of the resulting films is significantly modified. The deposited crystal phases change from rutile to anatase and the density and the refractive index decrease by a factor of about 1.3. The microstructure of the layers is strongly influenced by the sputtering pressure. An improvement of the hydrophilicity as well as of the photocatalytic activity can be observed, due to the changes in the structure of the layers.