OXIDATION STUDIES OF THE GRAPHITE SURFACE BY SCANNING-TUNNELING-MICROSCOPY AND PHOTOELECTRON-SPECTROSCOPY

Scanning tunneling microscopy and spectroscopy and X-ray photoelectron spectroscopy were used to study oxidation effects of nitric acid on highly oriented pyrolytic graphite surface. This treatment was performed at different temperatures and etching times with the aim of realizing local binding sites on the surface without creating deep defects. Then these three technics were found in good agreement to characterize the weakly oxidized surface. A wavy structure different from pure graphite at atomic scale was imaged by scanning tunneling microscopy. This modification was correlated to the presence of carboxylic groups on the surface revealed by X-ray photoelectron spectroscopy. Both spectroscopies of scanning tunneling and X-ray photoelectron demonstrated the vanishing of pi bands characteristic from sp2 graphitic hybridization. This was attributed to dehybridization corresponding to new bondings of the graphite carbons in the carboxylic groups.