We describe the synthesis of bilayer graphene thin films deposited on insulating silicon carbide and report the characterization of their electronic band structure using angle-resolved photoemission. By selectively adjusting the carrier concentration in each layer, changes in the Coulomb potential led to control of the gap between valence and conduction bands. This control over the band structure suggests the potential application of bilayer graphene to switching functions in atomic-scale electronic devices

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With the recent discovery of superconductivity in carbon nanotubes (CNTs), 1, 2 alkaline-metal-doped C 60 crystals, 3 and graphite intercalation compounds 4-6 (GICs) with relatively high transition temperatures, there is a strong interest in the influence of many-body interactions on the electron dynamics in these systems. Graphene is a sheet of carbon atoms distributed in a honeycomb lattice and is the building block for all of these materials;therefore it is a model system for this entire family. Recently, graphene has been isolated using exfoliation from graphite 7, 8 and graphitization of SiC, 9, 10 enabling, for the first time, the direct measurement of the manybody interactions fundamental to all of these carbon systems. These interactions could be especially interesting owing to the effectively massless, relativistic nature of the charge carriers, which follows from the linearity of the bands at the Dirac crossing energy E D = ħω D and the formal equivalence of the Schrödinger wave equation with the relativistic Dirac equation for graphene. 7,8,11