Influence of the D.C. Magnetron Sputter Deposition Process on the Photocatalytic Activity of Amorphous TiO_2 Thin Films

摘要

For photocatalytic thin film applications TiO_2 has become one of the important materials. The most active TiO_2 crystal phase is anatase, though also rutile and brookite show good photoac-tivity. Therefore, it is usually anatase or a mixture of rutile and anatase which is applied for powder or thin film catalysts. On the other hand it has been claimed, that amorphous films should not exhibit any or only a very low photocatalytic activity. We have deposited XRD amorphous thin films by d.c. magnetron sputtering from sub-stoichiometric TiO_(2-x) targets. The coatings are transparent and show a photocatalytic activity half of that of a thin layer of spin coated Degussa P25 powder which is opaque due to its high surface roughness. It was found that the photocatalytic activity of the films depended on deposition parameters like gas pressure and sputter power. A decrease in film density, as deduced from the refractive index and the microstructure, resulted in an increase in photocatalytic activity.