Photocatalytic TiO2 films were deposited by a hollow cathode gas-flow sputtering method using two Ti metal targets mounted parallel to each other. The Ar and O-2 flow rates were 3000 and 0-50 SCCM (SCCM denotes cubic centimeter per minute at STP), respectively, and total gas pressure during the deposition was maintained at 45 Pa. The highest deposition rate for the photocatalytic TiO2 films was 162 nm/min at 30 SCCM of O-2 flow. The as-deposited films and postannealed films, annealed in air at 300 degrees C for 1 h, were used to carry out photocatalytic decomposition of acetaldehyde (CH3CHO). In particular, the postannealed films showed extremely high photocatalytic activity compared to the photocatalytic activity of films deposited by conventional reactive sputtering. (C) 2008 American Vacuum Society.