Effect of local doping on the electronic properties of epitaxial graphene on SiC

Graphene grown on silicon carbide (SiC) is a promising material for high speed electronic devices. However, for possible future applications it is important to understand the electron properties of this material and how it is affected by the interaction with the SiC interface. Here we report an atomically resolved scanning tunneling microscopy and spectroscopy study of local structural and electronic properties of epitaxial graphene. Sharp localized states from the graphene/SiC(0001) interface have been found to strongly influence the electronic properties of the first graphene layer, causing local doping of graphene layer. The disordered high electron density states have originated from the underlying carbon-rich interface layer whose structure is discussed. Scanning tunneling microscopy images of a first graphene layer on SiC(0001) taken at bias voltage - 500 and 500mV (5×5 nm 2). Red circles and blue crosses indicate that localized states in the filled and empty electron states belonging to the underlying interface layer are located at different positions.