Epitaxial graphene on step bunching of a 6H-SiC(0001) substrate: Aromatic ring pattern and Van Hove singularities

We report on scanning tunneling microscopy and spectroscopy (STM/STS) investigations of graphene grown on a 6H-SiC(0001) substrate. Our STM images of a graphene layer on a step bunching of the SiC feature a (root 3 x root 3)R30 degrees pattern of aromatic rings and well developed, sharp Van Hove singularities in the corresponding STS spectra. High-resolution STM images show that the flake is discontinuous at the step edge. Simulations based on density functional theory indicate that the graphene edge is terminated armchair. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4796170]