Optical and structural characterization of aluminium doped zinc oxide thin films prepared by thermal evaporation system

Abstract

The process of mixing different weight ratios of aluminium (2, 4, and 6 wt%) and zinc powder – as the target material – was conducted in a vacuumed quartz tube. The sintering processing was completed by leaving the powder for 2 h in an oven at 1000 ᴼC, facilitating the manufacturing of homogeneous alloys. The posterior, prepared by vacuum evaporation, was deposited on a glass substrate. Next, the films were annealed at 200 ᴼC for 2 h. X-ray diffraction demonstrated that both the pure ZnO and ZnO:Al had a polycrystalline composition, with a dominate preferential direction of (101) for all models. The crystallite size of pure ZnO was 26.26 nm; aluminium doping at 2 wt% and 4 wt% led to a decrease in the crystallite size, to 19.24 nm. Further, the deformation increased to 6 wt%, leading to spherical nanoparticles with diameters in the range of (30–60) nm. With increases in the doping ratio, the nanoparticles become more conical, with bases of widths of (25–50) nm and heights of (100–225) nm. Optical measurements also showed a decrease in the optical transmittance and energy gap values. The occurrence of shifting at the Fermi level for ZnO and ZnO:Al were Ef = 0.427 eV and Ef = 0.667 eV, respectively.