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HL: Fachverband Halbleiterphysik

HL 50: Graphene and Carbon Nanotubes

HL 50.4: Vortrag

Donnerstag, 25. März 2010, 10:15–10:30, H15

Electronic structures and screening effects in bilayer graphene nanoribbons — •Hengyi Xu¹, Thomas Heinzel¹, and Igor Zozoulenko² — ¹Heinrich-Heine-Universität, Düsseldorf — ²Linköping University, Sweden

Graphene is considered as a promising material for future microelectronics in which the externally controllable of the resistance is crucial. To achieve this purpose, a number of mechanisms to induce an energy gap in single-layer graphene are proposed. Graphene bilayers, however, provide an alternative way to realize this task. Here, we study the electronic properties of bilayer graphene nanoribbons in the presence of a single gate using the tight-binding approach. The Coulomb interactions are incorporated in a self-consistent way within the Hartree approximation. We calculate the density and Hartree potential profiles and compare them with those of the single-layer graphene. It is shown that the fluctuations of the density and potential of bilayers are suppressed and their values decrease due to the Coulomb interaction between layers in contrast to the single-layer graphene. For sufficient thin dielectrics and high external voltages, the potentials of graphene layers diverge clearly and the differences grow linearly as gate voltages increases. This potential difference results in the electron-hole asymmetry of electronic spectrum and energy gaps around the neutrality point in the otherwise metallic graphene bilayers. The sizes of energy gaps are studied as a functions of external gate voltages. The relevant electrostatics of double- and single-gate geometries of bilayer is also discussed.