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°C - 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(Ωcm)^-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^oC - 700^oC. These mean that the optical quality of NiO films is improved by annealing

Nanosized Co₃O₄ thin films were prepared on glass substrates by using sol-gel spin coating technique. The effect of annealing temperature (400°C - 700°C) on structural, morphological, electrical and optical properties of Co₃O₄ thin films were studied by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Electrical conductivity and UV-visible Spectroscopy (UV-Vis). XRD measurements show that all the films are nanocrystallized in the cubic spinel structure and present a random orientation. Six prominent peaks, corresponding to the (111) phase (2θ ≈ 18.90°), (220) phase (2θ ≈ 31.29°), (311) phase (2θ ≈ 36.81°), (222) phase (2θ ≈ 38.54°), (400) phase (2θ ≈ 44.80°), (511) phase (2θ ≈ 59.37°) and (440) phase (2θ ≈ 65.27°) appear on the diffractograms. The crystallite size increases with increasing annealing temperature. These modifications influence the optical properties. The morphology of the sol gel derived Co₃O₄ shows nanocrystalline grains with some overgrown clusters and it varies with annealing temperature. The optical band gap has been determined from the absorption coefficient. We found that the optical band gap energy decreases from 2.58 eV to 2.07 eV with increasing annealing temperature between 400°C - 700°C. These mean that the optical quality of Co₃O₄ films is improved by annealing. The dc electrical conductivity of Co₃O₄ thin films were increased from 10^–4 to 10^–2 (Ω^.cm)^–1 with increase in annealing temperature. The electron carrier concentration (n) and mobility (μ) of Co₃O₄ films annealed at 400°C - 700°C were estimated to be of the order of 2.4 to 4.5 × 10¹⁹ cm^–3 and 5.2 to 7.0 × 10^–5 cm²^.V^–1^.s^–1 respectively. It is observed that Co₃O₄ thin film annealing at 700°C after deposition provide a smooth and flat texture suited for optoelectronic applications