Microstructures and complex impedance analysis of spray pyrolysis-synthesized Ni doped ZnO for optoelectronic applications

Abstract

This study focuses on the physical exploration, particularly examining the structural and electrical attributes of ZnO thin films produced through spray deposition, with variations in the Ni/Zn ratio (0.25 %, 0.5 %, and 0.75 %). X-ray diffraction (XRD) analysis reveals that both undoped and Ni-doped ZnO films exhibit a hexagonal crystalline structure, with a preferred orientation along the (002) direction perpendicular to the substrate. The semiconductor nature of all prepared compounds is confirmed by the grain boundary resistance. An escalation in Ni concentration corresponds to an increase in grain boundary resistance. The activation energy values, derived from both relaxation time and grain boundary resistances, closely align. Impedance studies indicate the presence of two relaxation processes within the compounds. The Nyquist diagram illustrates the emergence of semicircles, with decreasing radii at higher temperatures, indicating thermally activated semiconductor behavior in these samples, as evidenced by electrical conductance and distribution of relaxation times.