Optical constants and dispersion energy parameters of NiO thin films prepared by radio frequency magnetron sputtering technique

In this paper, we report on rf power induced change in the structural and optical properties of nickel oxide (NiO) thin films deposited onto glass substrates by rf magnetron sputtering technique. The crystallinity of the film was found to increase with increasing rf power and the deposited film belong to cubic phase. The maximum optical transmittance of 95% was observed for the film deposited at 100 W. The slight shift in transmission threshold towards higher wavelength region with increasing rf power revealed the systematic reduction in optical energy band gap (3.93 to 3.12 eV) of the films. The dispersion curve of the refractive index shows an anomalous dispersion in the absorption region and a normal dispersion in the transparent region. It was observed that the dispersion data obeyed the single oscillator of the Wemple-Didomenico model, from which the dispersion parameters, dielectric constants, relaxation time, and optical non-linear susceptibility were evaluated. We have made an attempt to discuss and correlate these results with the light of possible mechanisms underlying the phenomena. (C) 2013 AIP Publishing LLC.