Direct Observation of Interface States between Single Layer Graphene and SiC*

Graphite films grown on carbon-terminated SiC exhibit coherent transport properties that suggest potential for novel nanoelectronics applications [1]. However, for films grown on silicon-terminated SiC the coherence is greatly reduced, suggesting that the interface electronic structure influences the transport [1]. We have investigated the interface structure and electronic states that form in single layer graphene grown on silicon terminated SiC, using scanning tunneling microscopy and spectroscopy measurements at 4 K. Imaging a single graphene layer reveals features of both the graphite structure and the~SiC~interface. Which structure dominates is observed to be a function of the imaging bias. Sharp peaks in the density of states were found over SiC interface features, which correspond to the onset voltages observed in topography measurements. A comparison of experimental and theoretical findings will be discussed including relevance to transport measurements. *This work is supported in part by the Office of Naval Research and NSF. [1] C. Berger et al., Science 312, 1191 (2006); J. Phys. Chem. B 108, 19912 (2004).