Characterization of Graphene Films and Ribbons on Silicon Carbide

Ultrathin graphite films, 1-6 graphene layers thick, were grown on both the Si-terminated (0001) and C-terminated ($000\bar {1})$ faces of 4H- and 6H-SiC via thermal desorption of silicon in UHV. Through investigations of the thinnest films (monolayer graphene) by LEED and STM, we show the existence of a complex $\sqrt 3 \times \sqrt 3 R30^{\circ}$reconstructed layer between the lowest graphene layer and the SiC substrate. The $6\sqrt 3 \times 6\sqrt 3 R30^{\circ}$ LEED pattern obtained after annealing above $1250^{\circ}C$ can be explained predominantly by kinematic scattering from the slightly $6\times 6$ corrugated graphene, from the reconstruction, and from the SiC substrate. Low-order double-scattering is required to explain all of the diffraction features. LEED and STM on graphene ribbons patterned from these films (80-400 nm width) show that graphene layers remain intact after photolithography and plasma etching.