Structural and optical properties of RF sputtered ZnO thin films: Annealing effect

In this study, the effects of annealing temperature on morphological, optical and structural properties of Radio Frequency (RF) magnetron sputtered Zinc oxide (ZnO) thin films were investigated. X-ray diffraction spectra confirmed the hexagonal wurtzite structure with preferential orientation along the c-axis. The annealing temperature had an important role on the crystallite size and it was calculated as 19.7 nm, 17.2 nm, 15.1 nm and 24.5 nm, depending on the increasing annealing temperature. The optical transmittance of ZnO thin films ranged from 85% to 95% at 550 nm wavelength, and this change occurred linearly with annealing temperature. The optical band gap (E_g) of pure ZnO was 3.25 eV; this first decreased to 3.23 eV at low annealing temperature and then increased linearly to 3.26 eV with increasing annealing temperature.