Nickel-induced microwheel-like surface morphological evolution of ZnO thin films by spray pyrolysis

Abstract

Nickel–zinc oxide (Ni–ZnO) thin films were deposited onto glass and tin-doped indium oxide-coated glass substrates by using a pneumatic spray pyrolysis technique at 450 °C from aqueous solutions of zinc acetate and nickel acetate precursors. The effect of nickel doping on structural, morphological and optical properties of the ZnO thin films has been studied. The X-ray diffraction patterns confirmed the polycrystalline nature of the films having hexagonal crystal structure. Ni–ZnO films with appropriate nickel doping revealed the occurrence of novel wheel-like surface morphology. The absorption edge of the Ni–ZnO films showed a red shift, meaning that the optical band gap energy decreases as the nickel doping concentration increases. A growth model is developed and proposed for the novel wheel-like morphology. All the thin films exhibited room-temperature photoluminescence. Pure ZnO and Ni–ZnO thin films were tested for their photoelectrochemical performance in 0.5 M Na2SO4 electrolyte solution. The values of fill factor and open circuit voltage were improved for the Ni–ZnO thin films.