Thin film TiO2 photocatalyst deposited by reactive magnetron sputtering

TiO2 films were deposited by r.f. reactive magnetron sputtering on non-alkali glass at 200 °C under total gas pressure of 0.3, 1.0 and 3.0 Pa with oxygen flow ratio [O2/(O2+Ar)] of 30%. All films showed polycrystalline anatase structure, in which a small portion of rutile phase was observed only for the films deposited at 0.3 Pa. The films deposited at total gas pressure (ptot) of 3.0 Pa performed photoinduced hydrophilicity and high photocatalytic activities, i.e. photoinduced decomposition of acetaldehyde (CH3CHO) gas and adsorbed Methylene Blue on the film surface. The photocatalytic activity of the films showed the clear tendency to decrease with the decrease in ptot during the deposition. Such degradation of the photocatalytic activity was considered to be correlated with the transport processes of the high-energy particles in the sputter deposition processes. In the case of the lower ptot of 0.3 or 1.0 Pa, the films showed poor photocatalytic activities because of the defect level generations caused by the bombardment of the high-energy particles on the growing film surface. Such defect levels should be the recombination centers of the electron–hole pairs induced by the UV illumination and decrease their lifetime.