The interfacial structure of epitaxial graphene on Si-face SiC(0001) has been controversial since its first observation in the 1970s. In this work, we show that this interface is a warped graphene layer with periodic inclusions of pentagon-hexagon-heptagon (H5,6,7) topological defects within the honeycomb lattice. These H5,6,7 regions deviate locally from the honeycomb lattice of ideal graphene, relieving strain between the graphene layer and the SiC substrate, while still retaining the three-fold coordination for each carbon atom and providing local commensurability with the substrate. This model explains the consistencies and variation in the structural and electronic properties of the epitaxial graphene/SiC(0001), and ends the decades-long controversy on the nature of its interface.
Published in Physical Review Letters:
“Epitaxial Graphene on SiC(0001): More than Just Honeycombs“, Y. Qi, S. H. Rhim, G. F. Sun, M. Weinert, and L. Li, Phys. Rev. Lett. 105, 085502 (2010).