Microstructure and photoelectrochemical characterization of the TiO2-SnO2 system

The isostructural system of TiO2-SnO2 has recently emerged as a promising candidate for gas detection. Thin films of TiO2-SnO2 have been deposited onto different substrates at 620 K by the rf sputtering from a Ti-SnO2 target. In order to cover a full compositional range from 100% TiO2 to 100% SnO2 in the film, the target surface ratio of SnO2/Ti has been varied. The crystallographic structure and film morphology have been investigated by means of GID and AFM. The oxidation states of tin and titanium ions have been studied by the Mössbauer spectroscopy combined with XPS. From the photoelectrochemical kinetics, longer relaxation times have been found for TiO2-SnO2 than those for pure TiO2. The electron trap levels are proposed to account for this observation.