Microstructural and optical properties of Ni-doped ZnO thin films prepared by chemical spray pyrolysis technique

Abstract

In this study, multifunctional ZnO and Ni-doped ZnO thin films were prepared by chemical spray pyrolysis technique (SPT) on soda lime glass substrates at 300 °C. The liquid precursors for the films were synthesized from high purity zinc acetate (Zn (CH3COO)2.2H2O) and nickel acetate (Ni (CH3COO)2.3H2O). In order to vary the concentrations of the metallic constituents in the films, the precursors were prepared at 0.1 M, 0.15 M, 0.2 M and 0.25 M in distilled water. For the Ni-doped ZnO thin films, the mixing ratio of the precursor was in proportion of nickel acetate 0% to 10% by volume of the zinc acetate. Meanwhile, deposition parameters i.e. temperature, substrate distance and deposition time were optimized to achieve good quality thin films. Rutherford Backscattering spectroscopy (RBS) result shows an increase in oxygen content in ZnO film with 84% compared to Ni–ZnO thin films. The thickness of ZnO was observed to be lower than Ni–ZnO thin films, however a marginal increase in the thickness of Ni–ZnO thin film was observed with increase in Ni2+ content. Visual observation and spectrophotometer results indicated that the films are highly transparent in the UV-visible region. Ni–ZnO films were observed to have a higher transmittance than ZnO thin films, with increase in transmittance with Ni2+concentrations. The absorption edge of ZnO was observed to be lower than Ni–ZnO, and the optical band gap of undoped ZnO thin film decreased slightly from 3.28 eV to 3.20 eV of 10% Ni-doped ZnO thin film.