Energetic heterogeneity studies of the oxidized graphite surface by scanning tunneling microscopy and photoelectron spectroscopy

Scanning tunneling microscopy and spectroscopy (STM/STS) and X-ray photoelectron spectroscopy (XPS) are used to study oxidation effects of nitric acid on an HOPG surface. Various temperatures and etching times are applied in order to create local binding sites on the surface without creating deep defects. A wavy structure, different from pure graphite at atomic scale, is shown by STM. This can be explained by the presence of carboxylic groups on the surface, revealed by XPS. Both STS and XPS demonstrate the vanishing of bands characteristic of sp2 graphite hybridization. This, in turn, can be explained by dehybridization related to new bondings of the graphite carbons in the carboxylic groups. An important result of area averaging spectroscopy is the observed energetic heterogeneity of the oxidized surface.