Effect of annealing temperature on the growth of Zn-Sn-O nanocomposite thin films

The Zn-Sn-O (ZTO) nanocomposite thin films were annealed at 300-1000 °C to study the annealing temperature effects on the film optical and structural properties. The XRD analysis shows that the films composition largely depends on the annealing temperature. The spinel zinc stannate Zn2SnO4 was obtained from 400 to 700 °C, the perovskite-type zinc stannate ZnSnO3 appeared at 800 °C, and the Zn2SiO4 can be generated only above 1000 °C. In addition, lattice parameter, grain size and microstrain were investigated to understand the influence of annealing temperature on the film property. The average transmittance of the ZTO films is among 80%-96%, and the film optical band gap increases from 3.55 to 4.09 eV with temperature increases from 300 to 1000 °C. First-principles calculation confirms that the band gap increase can be ascribed to the phase transition from Zn2SnO4 to ZnSnO3. Our work suggests that the ZTO film property can be well engineered by controlling the annealing temperature.