The Impact of Local Heating on the Oxidation Process of Cobalt Nanowires

The process of oxidation of cobalt (Co) nanowires leading to the formation of different oxides (CoO an Co3O4) was investigated. The transition from CoO to Co3O4 was studied by X-ray diffraction analysis and Raman spectroscopy techniques. Only Co3O4 reflexes were detected in the X-ray diffraction patterns after annealing nanowires at 360°C, which confirms the complete conversion to cobalt tetroxide. A similar result was observed upon exposure to laser radiation, where local heating induced by the laser also led to the transition from CoO to Co3O4. Two Raman spectra of cobalt tetroxide were demonstrated with a relative shift of 20 cm–1 depending on the degree of crystallization at different excitation laser powers.