Growth and characterization of Cobalt Oxide thin films

Thin films of cobalt were deposited on glass substrates at room temperature using an electron beam evaporation technique. Formation of different cobalt nanostructures has been carried out by controlled thermal oxidation of the as-deposited Co films in controlled ambient condition. Oxidation temperature was varied within a range up to 700 °C. Structure and morphology of the oxide films along with their chemical and electrical properties have been investigated using various surface characterization techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and I-V measurements. All results are in good correlation and suggest that the CoO phase is only stable for a lower oxidation temperature below 400 °C whereas Co3O4 phase usually appears at higher oxidation temperature. Moreover, the average crystallite size of the oxide nano-particles increases with the oxidation temperature and duration. Electrical measurement shows that resistance of cobalt oxide thin films decreases with an increase in oxidation temperature and duration. All these findings can be explained in terms of thermal diffusion related to different surface morphologies and grain size effects.