The effect of substrate temperature on the structural, morphological, optical and electrical properties of CO3O4 thin films

This study aims to create cobalt oxide layers using the spray pyrolysis approach. During this process, a cobalt chloride (COCl2.6H2O) aqueous solution is sprayed onto preheated glass substrate at temperatures in the range of 250°C to 400°C. To evaluate and characterize the structural, optical, morphological, and electrical characteristics of the samples, several techniques were employed, including X-ray diffraction (XRD), scanning electron microscopy, optical absorption measurements, and the four-point probe process. Structural analysis of the X-ray diffraction displayed that Co3O4 developed in a controlled manner, forming a cubic structure. The films were found to grow preferentially along the (111) or (331) directions depending on the temperature of the substrate. Furthermore, (XRD) analysis clearly indicated that the average Co3O4 grain size increased with higher substrate temperatures. Observations of the surface morphology indicated some overgrowth of cobalt oxide clusters alongside the presence of nanocrystalline grains, and small spherical particles are well distributed at both substrate temperatures of 250°C and 400°C. Optical studies revealed direct bandgap values ranging from 1.46 to 2.05 eV. The highest conductivity measured was 1.29 S/cm at a temperature of 400 °C. It's observed that as the substrate temperature rises, the electric conductivity of the prepared samples also increases.