Role of covalent and metallic intercalation on the electronic properties of epitaxial graphene on SiC(0001)

We present an orbital-resolved density functional theory study on the electronic properties of hydrogen and lithium intercalated graphene grown on the Si face of SiC. Starting from the (6√3×6√3)R30^∘ surface reconstruction of the graphene/SiC heterosystem, we find that both H and Li can restore the ideal structural characteristics of the two nonequivalent junction parts (i.e., graphene and the SiC substrate) when inserted at the interface. However, the chemical and electrostatic interactions remain different for the two cases. Hence, H-intercalated epitaxial graphene is subject to a sublattice symmetry-breaking electronic interference that perturbs the Dirac point, whereas Li intercalation gives rise to a highly n-doped system due to a nonuniform delocalization of Li charges. Results bring to discussion the role of substrate engineering in epitaxial graphene on SiC.