Electron spectroscopy of graphite, graphite oxide and amorphous carbon

Abstract

Core-level and valence-band photoelectron spectra and Auger spectra for the basal plane of highly ordered graphite, the edge plane of highly ordered graphite, the basal plane of graphite oxide, and for the basal plane of disordered graphite are compared in an effort to determine spectral features that may be used to identify these chemical species in carbon-rich specimens. The photoelectron spectra were recorded using 1253.6 eV X-ray excitation. The Auger spectra were obtained using both X-ray (1253.6 eV) and electron (3 keV) excitation. The differential X-ray excited C-KVV spectra were the most useful in distinguishing the different types of carbon. In particular, the plasmon structure and the energy separation between the two major excursions were very sensitive to changes in the surface chemistry and structure. Changes in peak position and peak width observed in the valence band and C(1s) photoelectron spectra were also very helpful in distinguishing the pristine, structurally damaged, and the oxidized graphite surfaces. Much of the structural and chemical information apparent in the X-ray excited C-KVV spectra was lost upon electron beam exposure. Differences in the C-KVV Auger lineshapes for X-ray and electron excitation were attributed to both structural and chemical changes induced by electron beam exposure.