Investigation of aluminum doping on structural and optical characteristics of sol–gel assisted spin-coated nano-structured zinc oxide thin films

Abstract

In this research, Al-doped (with 2, 4, 6, and 8 mol%) zinc oxide thin films deposited onto glass substrates using wet chemical spin coating technique were characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and UV–Vis spectroscopic methods to realize the doping effect of Al on structural and optical properties of ZnO thin films. XRD analysis revealed that the Al-doped ZnO (AZO) thin films were polycrystalline in nature with hexagonal lattice structure, and crystallite growth along c-axis. SEM images on the film surface at lower Al content exhibited granular nanostructures. At higher Al content, the nanostructural features of ZnO thin films was observed to be diminished. The compositional analysis via EDS measurements indicated the presence of zinc, oxygen, and aluminium into the AZO thin films. AZO thin film containing 2 mol% Al exhibited higher transmittance of 97% and absorption edge at 385 nm in the visible region. Optical bandgaps of AZO thin films were varied within 3.30–3.37 eV. Noticeable variations on structural features, and optical parameters of AZO thin films were detected, and the changing trend showed was non-linear and non-monotonic in nature.