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

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 degrees C, 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 degrees C 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 E-f = 0.427 eV and E-f = 0.667 eV, respectively.