Nanopatterning on highly oriented pyrolytic graphite surfaces promoted by cobalt oxides

In this work we present a method to produce nanopatterning on graphite surfaces via carbon gasification reaction, with oxygen as reactant gas, catalyzed by cobalt oxides (CoO) instead of metallic cobalt nanoparticles as most usual methods. This reaction is produced at 400 °C, temperature which is much lower than that used in conventional methods. The chemical analysis of the cobalt species have been performed with X-ray photoemission and X-ray absorption spectroscopies, which are supported by theoretical cluster model and multiplet calculations of the spectra. The changes in the morphology of the surfaces after each process have been followed by atomic force microscopy. The defects produced after the gas reaction on the graphite surface have also been analyzed by combining atomic force microscopy and confocal micro-Raman spectroscopy. The presence of oxygen in the initial CoO wetting-layer has been identified as responsible of the weakening of the graphite bonds at the surface.