Precursor-Dependent Spray-Pyrolyzed Co3O4 Thin Films: Comparative Results on Their Structural, Optical, and Electrical Properties

The paper reports the comparative results on the structural, optical, and electrical characteristics of precursor-dependent spray-pyrolyzed Co3O4 thin films. X-ray diffraction analysis confirms the cubic spinel Co3O4 structure of both films. Williamson-Hall plot analysis reveals that the Co3O4 film prepared using cobalt chloride is of crystallite size 28.59 nm and undergoes tensile strain, while the film prepared using cobalt nitrate is of crystallite size 10.53 nm and undergoes compressive strain. Using Kubelka–Munk treatment, the band gap energies corresponding to ligand–metal charge transfer events O2−  → Co3+ and O2−  → Co2+ are found to be 1.61 and 2.05 eV in the film prepared using cobalt chloride and 1.68 and 2.15 eV in the film prepared using cobalt nitrate respectively. The study of the temperature dependence of the resistance reveals that the films prepared using cobalt chloride and cobalt nitrate have activation energies of 0.091 and 0.161 eV in the lower temperature region and 1.284 and 1.383 eV in the higher temperature region, respectively.