The effect of Zn2+ on the anion vacancies in ZnO thin-films grown using chemical bath deposition.

Abstract

Zinc Oxide (ZnO) thin-films were grown on glass substrate using chemical bath deposition method (CBD) from precursors containing varying molar concentrations of zinc acetate. The structure, morphology, optical and luminescence properties of the films were investigated using X-ray diffraction (XRD), Scanning electron microscopy (SEM), Ultraviolet visible spectroscopy (UV/VIS/NIR) and Photoluminescence spectroscopy (PL). The XRD result showed that at low molar concentrations of zinc acetate the structure consists of Zn(OH)2 and ZnO phases. As the molar concentration of zinc acetate increases the well-known hexagonal wurtzite structure of ZnO was developed. The average crystalite size estimated using Scherrer’s formula was about 41.19 nm. It was found that the average crystallite size increased with an increase in the molar concentration of zinc acetate. SEM observations showed the presence of nanoparticles forming aggregated nanoflakes. The surface morphology was found to be dependent on the concentration of zinc acetate. The UV-Vis spectra showed that the absorption band edge shift to the higher wavelength with an increase in molar concentration of zinc acetate. The band gap energy of ZnO thin-films determined from UV reflectance spectra was found to decrease from 3.17 to 2.73 eV with an increase in the zinc acetate concentration. The PL results showed that the luminescence intensities decrease with an increase in the molar concentration of zinc acetate without any noticeable shift in position.