Nanosized Co 3 O 4 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 Co 3 O 4 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 Co 3 O 4 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 Co 3 O 4 films is improved by annealing. The dc electrical conductivity of Co 3 O 4 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 Co 3 O 4 films annealed at 400°C - 700°C were estimated to be of the order of 2.4 to 4.5 × 10 19 cm –3 and 5.2 to 7.0 × 10 –5 cm 2 . V –1 . s –1 respectively. It is observed that Co 3 O 4 thin film annealing at 700°C after deposition provide a smooth and flat texture suited for optoelectronic applications.
KeywordsSol Gel MethodStructural PropertiesOptical PropertiesElectrical Properties
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Synthesis and Characterization of Co<sub>3</sub>O<sub>4</sub> Thin Film — Oak Academic Publishing