Quasi-Free-Standing Epitaxial Graphene on SiC Obtained by Hydrogen Intercalation

Abstract

Quasi-free-standing epitaxial graphene is obtained on SiC(0001) by hydrogen intercalation. The hydrogen moves between the $(6\sqrt{3}\times 6\sqrt{3})\mathrm{R}30°$ reconstructed initial carbon layer and the SiC substrate. The topmost Si atoms which for epitaxial graphene are covalently bound to this buffer layer, are now saturated by hydrogen bonds. The buffer layer is turned into a quasi-free-standing graphene monolayer with its typical linear $\pi$ bands. Similarly, epitaxial monolayer graphene turns into a decoupled bilayer. The intercalation is stable in air and can be reversed by annealing to around $900°\mathrm{C}$.