Study of Structural and Optical Properties of Ni(1-x) Znx O Thin Films Prepared by Chemical Spray Pyrolysis Method

Abstract

Pure NiO and NiO doped with Zn with volume percentage doping of (2, 4, 6 and 8 %) have been prepared by chemical spray pyrolysis method on glass substrates at a temperature of (370 ºC). The effect of Zn doping on structural and optical properties has been investigated. XRD results showed that all the films were polycrystalline in nature and had a cubic structure with preferred orientation along (111) plane for all doping percentages except the films of 4% doping percentage where the preferred orientation was along the (200) plane. It was found that doping with Zn led to decrease in the intensity of (111) peak, while the average grain size increases as Zn concentration increases. In order to study the optical properties, the absorbance and transmittance spectra have been recorded in the wavelength range of (300-900) nm. The optical energy gap for allowed direct electronic transition was calculated using Tauc equation and it is found to be (3.59 eV) for undoped NiO thin films. However, the increase in doping percentage causes an increase in the value of the energy gap and it reaches (3.75 eV) for the doping percentage of (8%). These values were in good agreement with the values of energy gap obtained by taking the values of energy correspond to the peak of the first derivative of absorbance with respect to energy versus energy curve. In order to investigate the behavior of refractive index as a function of wavelength, two empirical models have been adopted namely Cauchy’s and Sellmeier’s equations. The static refractive indices for all samples were calculated using these models.