Epitaxial graphene on SiC(0001): It takes a Si jump

Using scanning tunneling microscopy with transition metal (Fe, Cr)-coated W tips and first-principles calculations, we have recently shown that interface of epitaxial graphene/SiC(0001) is a warped graphene layer with periodic inclusions of hexagon-pentagon-heptagon (H$_{5,6,7})$ defects that break the six-fold honeycomb symmetry [1]. Here we show that this unique structure facilitate a novel pathway for the disposal of Si during growth: the diffusion of Si vertically through the warped interfacial layer via a series of configurations that involve the dissociation and formation of C-C and Si-C bonds within the pentagon and heptagon of the H$_{5,6,7}$ complex. The calculated energy barrier for this diffusion path is 4.7 eV. These results and their implications on the self-limiting growth of epitaxial graphene on SiC(0001) will be presented at the meeting. \\[4pt] [1] Qi et al., Phys. Rev. Lett. \textbf{105}, 085502 (2010).