Annealing effects on the structural, electrical and optical properties of ZnO thin films prepared by thermal evaporation technique

Zinc oxide (ZnO) thin films have been prepared on glass substrates at room temperature by thermal evaporation technique using ZnO powders and then are annealed at different temperatures ranging from 200 °C to 500 °C for 2 h in air. The effect of the annealing temperature (Tr) on the structural, optical and electrical properties of the ZnO thin films was studied. Experimental results show that annealing temperature has an important role in the changes observed in the structural, optical and electrical properties of the ZnO thin films. The XRD measurements confirm that the thin films grown by this technique have good crystalline hexagonal wurtzite structures. The optical transmittance spectra show transmittance higher about ∼90% within the visible wavelength region. Hence, the values of the gap are found to be between 3.13 and 3.25 eV. The resistivity values of the films have changed between 2.10−3 and 4.10−2 Ω cm with annealing temperature