Preparation and characterization of ZnO–TiO2 films obtained by sol-gel method

Abstract

The sol-gel route has been applied to obtain ZnO–TiO2 thin films. For comparison, pure TiO2 and ZnO films are also prepared from the corresponding solutions. The films are deposited by a spin-coated method on silicon and glass substrates. Their structural and vibrational properties have been studied as a function of the annealing temperatures (400–750°C). Pure ZnO films crystallize in a wurtzite modification at a relatively low temperature of 400°C, whereas the mixed oxide films show predominantly amorphous structure at this temperature. XRD analysis shows that by increasing the annealing temperatures, the sol-gel Zn/Ti oxide films reveal a certain degree of crystallization and their structures are found to be mixtures of wurtzite ZnO, Zn2TiO4, anatase TiO2 and amorphous fraction. The XRD analysis presumes that Zn2TiO4 becomes a favored phase at the highest annealing temperature of 750°C. The obtained thin films are uniform with no visual defects. The optical properties of ZnO–TiO2 films have been compared with those of single component films (ZnO and TiO2). The mixed oxide films present a high transparency with a slight decrease by increasing the annealing temperature.