In this paper a systematic study has been carried out on the influence of thickness on the physical properties of nanocrystalline nickel oxide (NiO) thin films prepared on glass substrate by spray pyrolysis method. The prepared nanocrystalline NiO films were characterized using X-ray diffraction technique (XRD), field emission scanning electron microscopy (FESEM) and optical measurement techniques. XRD patterns reveal the cubic structure for all the samples and the crystallite size varies with the thickness. FESEM images confirmed that all the films are homogeneous, without any crack, dense and exhibit almost complete coverage of the substrate. The optical parameters such as transmittance, absorption coefficient and energy band gap of the films as a function of film thickness was investigated by UV-Vis spectrophotometer. The band gap of the films is found to be direct allowed transition and the variation of band gap values of nanocrystalline NiO thin films were found to be in the range of 3.48 eV to 3.53 eV.

Keywords: Nickel Oxide; Spray Pyrolysis Technique; Optical Properties;