Imaging the interface of epitaxial graphene with silicon carbide via scanning tunneling microscopy

Graphene grown epitaxially on SiC has been proposed as a material for carbon-based electronics. Understanding the interface between graphene and the SiC substrate will be important for future applications. We report the ability to image the interface structure beneath single-layer graphene using scanning tunneling microscopy. Such imaging is possible because the graphene appears transparent at energies of $\ifmmode\pm\else\textpm\fi{}1\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ above or below the Fermi energy $({E}_{F})$. Our analysis of calculations based on density-functional theory shows how this transparency arises from the electronic structure of a graphene layer on a SiC substrate.