UV–visible studies of nickel oxide thin film grown by thermal oxidation of nickel

In this work, we report an experimental study on optical properties of nickel oxide thin film by UV–visible spectroscopy. The nickel oxide thin film is grown by the oxidation of nickel deposited on ITO (tin doped indium oxide) coated glass substrate. The phase formation and electrical properties are studied with XRD and electrometer, respectively. On heat treatment at 500 °C for 4 h under oxygen atmosphere, most of the nickel is oxidized to nickel oxide. From the XRD analysis, we observe that, the (1 1 1) peak evolved as the most intense peak for nickel oxide contrary to (2 0 0) peak as previously reported (Dongliang Tao and Fei Wei, 2004; Hotovy et al., 2004; Lili et al., 2004 [1], [2] and [3]). The small oscillations in the absorbance spectra correspond to the constructive and destructive interferences of the reflected beam. The broad absorbance band below optical band gap energy is due to defects in the film. The band gap energy for NiO is calculated to be ∼3.6 eV.