Bilayer graphene: gap tunability and edge properties

Abstract

Bilayer graphene -- two coupled single graphene layers stacked as in graphite -- provides the only known semiconductor with a gap that can be tuned externally through electric field effect. Here we use a tight binding approach to study how the gap changes with the applied electric field. Within a parallel plate capacitor model and taking into account screening of the external field, we describe real back gated and/or chemically doped bilayer devices. We show that a gap between zero and midinfrared energies can be induced and externally tuned in these devices, making bilayer graphene very appealing from the point of view of applications. However, applications to nanotechnology require careful treatment of the effect of sample boundaries. This being particularly true in graphene, where the presence of edge states at zero energy -- the Fermi level of the undoped system -- has been extensively reported. Here we show that also bilayer graphene supports surface states localized at zigzag edges. The presence of two layers, however, allows for a new type of edge state which shows an enhanced penetration into the bulk and gives rise to band crossing phenomenon inside the gap of the biased bilayer system.

8 pages, 3 fugures, Proceedings of the International Conference on Theoretical Physics: Dubna-Nano2008

References in corpus (14)

• Electric Field Effect in Atomically Thin Carbon Films
• The electronic properties of graphene
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• Biased bilayer graphene: semiconductor with a gap tunable by electric field effect
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• Asymmetry gap in the electronic band structure of bilayer graphene
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• Localized states at zigzag edges of bilayer graphene
• Low density ferromagnetism in biased bilayer graphene
• Transmission through a biased graphene bilayer barrier
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• Magnetic structure at zigzag edges of graphene bilayer ribbons

Cited by in corpus (6)

• Energy gap tuning in graphene on hexagonal boron nitride bilayer system
• Strain-tunable band gap in graphene/h-BN hetero-bilayer
• Random gap model for graphene and graphene bilayers
• Diffusion in the random gap model of mono- and bilayer graphene
• Quantum Hall activation gaps in bilayer graphene
• Gaps and tails in graphene and graphane