Interlayer interaction and π-band electron occupation on top layers of freshly cleaved bulk HOPG investigated with N(E) C KVV Auger electron spectroscopy

N(E) C KVV Auger spectra (V = σsσpπ) were used for measurement of the π-band electron occupation of five outer layers on freshly cleaved bulk HOPG. The π-band electron occupation of the 1-5 graphene layers was measured relative to the electron concentration in the σp-band. In-depth π-band profiles were obtained by means of variation of the Auger electron takeoff angle within the range of 15-90°. Differences in the π-band electron occupation of the 1-5 graphene layers were determined. The π-band electron occupation varies from 0 at the top graphene layer to that of the π-band electron occupation typical for bulk HOPG at the 5th graphene layer counted from the outer surface. These results are discussed on the basis of the π-band formation under the interlayer interaction of the pz-electrons.