Dependence of electronic properties of epitaxial few-layer graphene on the number of layers investigated by photoelectron emission microscopy

We used spectroscopic photoemission and low-energy electron microscopy to investigate the electronic properties of epitaxial few-layer graphene grown on 6H-SiC(0001). Photoelectron emission microscopy (PEEM) images using secondary electrons (SEs) and C 1s photoelectrons can discriminate areas with different numbers of graphene layers. The SE emission spectra indicate that the work function increases with the number of graphene layers and that unoccupied states in the few-layer graphene promote SE emission. The C 1s PEEM images indicate that the C 1s core level shifts to lower binding energies as the number of graphene layers increases, which is consistent with the reported thickness dependence of the Dirac point energy.