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

TL;DR

This study uses density functional theory to analyze how hydrogen and lithium intercalation affect the electronic properties of epitaxial graphene on SiC, revealing different doping and symmetry effects.

Contribution

It provides a detailed orbital-resolved analysis of how covalent and metallic intercalation modify the electronic structure of epitaxial graphene on SiC.

Findings

Hydrogen intercalation breaks sublattice symmetry, perturbing the Dirac point.

Lithium intercalation results in high n-doping due to charge delocalization.

Both intercalants restore structural characteristics of the graphene/SiC interface.

Abstract

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 $(6\sqrt3\times6\sqrt3)R30^{\circ}$ 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/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.