Effect of Cu, Co, and Pb doping on physical properties of ZnO Zinc Blende and Hexagonal mixed phases thin films prepared by spray pyrolysis

Abstract

Here we report the preparation of the Zinc Blende ZnO phase mixed with a small ratio of the Wurtzite phase. The spray pyrolysis technique has been employed for all films deposited onto amorphous glass substrates. The XRD results revealed the formation of mixed ZnO Zinc Blende (ZB) and Wurtzite (WU) phases with the ZB phase as the predominant phase. The crystallite size of both phases had estimated using Scherer’s equation and both phases were found to have the same crystallite size. The FE-SEM images show the formation of grain sizes bigger than those recorded from Scherer’s equation. XPS results confirm the existence of doped elements in the deposited films with different ratios. The optical band gap of the pure film was estimated and found to be 3.24 eV. Upon doping the band gap optical has been decreasing to 3.2 eV for Cu-doped ZnO and 3.22 and 3.24 eV for Pb and Co-doped films. The refractive index dispersion was found to change from normal to anomalous behavior for a pure film as the wavelength increases. Cu and Pb-doped films show dispersion relation and Co-doped film shows normal behavior. Also, the high-frequency dielectric constant has been determined and found to decrease upon all doping elements as compared to pure film.