New process for synthesis of nickel oxide thin films and their characterization

Sol–gel spin coating method has been successfully employed for the deposition of nanocrystalline nickel oxide (NiO) thin films. The films were annealed at 400–700 °C for 1 h in an air and changes in the structural, morphological, electrical and optical properties were studied. The structural properties of nickel oxide films were studied by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD analysis shows that all the films are crystallized in the cubic phase and present a random orientation. Surface morphology of the nickel oxide film consists of nanocrystalline grains with uniform coverage of the substrate surface with randomly oriented morphology. The electrical conductivity showed the semiconducting nature with room temperature electrical conductivity increased from 10−4 to 10−2 (Ω cm)−1 after annealing. The decrease in the band gap energy from 3.86 to 3.47 eV was observed after annealing NiO films from 400 to 700 °C. These mean that the optical quality of NiO films is improved by annealing.

► NiO thin films are prepared by sol–gel spin coating technique. ► NiO exhibits hexagonal wurtzite structure. ► The room temperature electrical conductivity of NiO is of 10−6–10−5(Ω cm)−1. ► Optical studies show NiO has high absorption coefficient (104 cm−1).