On the transient photoconductivity behavior of sol–gel TiO2/ZnO composite thin films

• TiO2/ZnO composite films and pure TiO2 and ZnO were prepared by the sol–gel method.
• Transient photoconductivity was studied both in vacuum and in air.
• Environment influences significantly the shape of the photoconductivity responses.
• Some composites and pure TiO2 show a significant photoconductivity decrease in air.

The transient photoconductivity of TiO2/ZnO nanocomposite thin films was studied at 300 K, both in vacuum and in air. The samples deposited on quartz substrates were prepared via the sol–gel technique and calcinated at 500 °C for 1 h. For comparison, pure TiO2 and ZnO films were also synthesized. The XRD patterns of pure TiO2 and ZnO films revealed the formation of anatase TiO2 and wurtzite hexagonal ZnO, respectively. The nanocomposite Ti75Zn25O presented anatase phase only, while Ti25Zn75O and Ti50Zn50O presented amorphous phases. The pure TiO2 photoconductivity amplitude in vacuum is more than two and half orders of magnitude larger than that in air. Although no significant difference between the ZnO photoconductivity amplitudes in vacuum and in air is observed, the decay is obviously faster in air. For TiO2/ZnO nanocomposites, both in vacuum and in air, a considerable reduction in the photoconductivity amplitudes, especially for Ti50Zn50O sample, is shown.