| AVS 57th International Symposium & Exhibition | |
| Graphene Focus Topic | Tuesday Sessions |
| Session GR-TuP |
| Session: | Graphene Focus Topic Poster Session |
| Presenter: | J.E. Rowe, North Carolina State University |
| Authors: | A. Sandin, North Carolina State University A. Pronshinske, North Carolina State University D.B. Dougherty, North Carolina State University J.E. Rowe, North Carolina State University |
| Correspondent: | Click to Email |
Constant current tunneling spectroscopy has been used to study the high energy unoccupied electronic structure of single layer and bilayer epitaxial graphene on the Si-terminated face of SiC(0001) prepared with several different sample-annealing conditions that give different thicknesses of graphene film coverage. We identify a series of intense peaks in vertical sample-tip spacing versus voltage as derived from image-potential states of epitaxial graphene. These peaks shift in energy position between single-layer and bilayer graphene in a manner somewhat like the known work function difference (of ~4.4 eV and ~4.6 eV for single-layer and bilayer graphene respectively). We compare the series of image-potential-like-state energies measured experimentally with simple models of the tunneling potential due to a sharp tip protrusion and a flatter average tip radius that shows a variability of the energy series with spatial variation of the potential. In addition, we argue that variability in peak positions for nearly all of the observed image potential derived states arises from the variations in the 3-D tip shape, which then determines the filed dependent tunneling potential.