Preparation and characterization of nanostructured nickel oxide thin films by spray pyrolysis

Transparent crystalline nanostructured nickel oxide (NiO) thin films were prepared using a simple spray pyrolysis technique from hydrated nickel chloride salt solution (NiCl2·6H2O) onto glass and silicon (n-type) substrates at different temperatures (280, 320, 360, and 400 °C) and with different solution concentrations (0.025, 0.05, 0.075, and 0.1 M). Structural and morphological properties of the grown NiO films were studied using X-ray diffraction (XRD) and atomic force microscope. Optical properties and chemical analysis of the films were characterized by UV–visible absorption spectra and Fourier transform infrared spectroscopy, respectively. The XRD result showed that the deposited film has an amorphous structure when deposited at temperature of T s = 280 °C and concentration of 0.025 M. At higher temperatures (T s = 320, 360, 400 °C) and solution concentrations (0.05, 0.075, 0.1 M), the deposited films have cubic polycrystalline structure formed with preferred orientation along (111) plane. The band gap of NiO film increases from 3.4 to 3.8 eV as the molarity decreased from 0.1 to 0.05 M.