Influence of Ni doping on the morphological, structural, optical and electrical properties of CuO thin films deposited via a spray pyrolysis

Abstract

Nanostructured copper oxide (CuO) and Nickel (Ni)-doped CuO thin films with different concentrations of Ni ranging from 2 to 8 at.% were synthesized onto a plain glass substrate at the substrate temperature, 350 °C by a thermal spray pyrolysis technique. Field emission scanning electron microscopy (FESEM) analysis of CuO and Ni-doped CuO thin films detected the closely spaced rock-like nanostructures, evenly distributed on the film surfaces. The average particle sizes of CuO and Ni-doped CuO thin films were calculated from the FESEM and found between 260 and 63 nm. Energy-dispersive X-ray analysis revealed that CuO and Ni-doped CuO thin films were stoichiometric and typically comprised of Cu, O, and Ni. X-ray diffraction analysis showed the monoclinic structure of the films with the most preferred orientation plane ( 1 ‾ 11) along with the (111), ( 2 ‾ 02) and (02 2 ‾ ) crystalline planes. The maximum crystallite size was found at about 81 nm for 6 at% Ni-doped CuO thin film. CuO film showed an optical transmittance of about 33% in the visible-NIR region. Ni-doping enhanced the absorbing nature of CuO thin films in the vis-NIR region of light. With the rise of Ni content in CuO thin films, the optical bandgap gradually increased from 2.28 to 2.78 eV. Resistivity raised from 9.28 × 10 3 to 49.01 × 10 3 Ω-cm with the increase of the amount of Ni. • The FESEM micrographs show that the thin film surface of the CuO and nickel (Ni)-doped CuO thin films comprises irregularly shaped nanoparticles that aggregate to form the columnar surface's morphology. • As the Ni increased in the precursor solution for the preparation of Ni-doped CuO thin films, EDX analysis of the prepared films showed an increase in Ni's mass and atomic percentage. • The films' monoclinic structure with the preferred orientation along with the ( 1 ‾ 11) crystalline plane is shown in the X-ray diffraction analysis. • Ni-doping enhanced the absorbing nature of CuO thin films in the vis-NIR region of light. • The optical band gap and electrical resistivity gradually increased with an increase in the CuO thin film's Ni content.