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

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.