Revealing the atomic structure of the buffer layer between SiC(0001) and epitaxial graphene

摘要

On the SiC(0001) surface (the silicon face of SiC), epitaxial graphene isobtained by sublimation of Si from the substrate. The graphene film isseparated from the bulk by a carbon-rich interface layer (hereafter called thebuffer layer) which in part covalently binds to the substrate. Its structuraland electronic properties are currently under debate. In the present work wereport scanning tunneling microscopy (STM) studies of the buffer layer and ofquasi-free-standing monolayer graphene (QFMLG) that is obtained by decouplingthe buffer layer from the SiC(0001) substrate by means of hydrogenintercalation. Atomic resolution STM images of the buffer layer reveal that,within the periodic structural corrugation of this interfacial layer, thearrangement of atoms is topologically identical to that of graphene. Afterhydrogen intercalation, we show that the resulting QFMLG is relieved from theperiodic corrugation and presents no detectable defect sites.