Synthesis of cobalt oxide (Co₃O₄) thin films by electrostatic spray pyrolysis technique (ESP)

The fabrication of cobalt oxide (Co₃O₄) thin films has received considerable attention. The crystalline quality of Co₃O₄ plays an important role in the properties of the fabricated film. This paper reports on the performance of a local electrostatic spray pyrolysis system to prepare Co₃O₄ thin films on glass substrates. The effect of applying an electric field during deposition on the structural growth and optical properties of Co₃O₄ thin films was studied. An improvement in the structure and optical properties was observed for the films deposited using an electric field, primarily because of the reduction in the droplet size. The results showed that applying a suitable electric field led to films formed with a smoother surface that were highly crystalline, with larger grain size, higher stoichiometry, and good optical properties that differed from those of the Co₃O₄ film deposited with no electric field. It was found that the grain size increased with the applied electric field. Optical absorption results revealed direct and indirect transitions for the Co₃O₄ thin films, and the band gap energy decreased with the applied electric field.