Characterization of titanium–tin composite oxide films and their visible-light photocatalytic properties Original Research Article

Bilayer structures of Ti film on SnOx film prepared by magnetron sputtering were annealed in ambient oxygen. Depth profiles of compositional elements after oxidation of the Ti/SnOx structures analyzed by XPS reveal that TiOx/SnOx composite films and TiO2/SnOx bilayer films were formed when the Ti/SnOx bilayer structures were fabricated at RT and 300 °C, respectively. In the TiOx/SnOx composite films, the SnOx forms impurity levels in the TiOx bandgap at the same time as it prevents TiO2 crystallization. These impurity levels are considered to play a role of visible-light absorption. Visible-light response photocatalytic activities are observed only in the TiOx/SnOx composite films.