Proximity Mechanisms in Graphene: Insights from Density Functional Theory

Abstract

One of the challenges in graphene fabrication is the production of large scale, high quality sheets. To study a possible approach to achieve quasi-freestanding graphene on a substrate by the intercalation of alkali metal atoms, Cs intercalation between graphene and Ni(111) is investigated. It is known that direct contact between graphene and Ni(111) perturbs the Dirac states. Cs intercalation restores the linear dispersion characteristic of Dirac fermions, which agrees with experiments, but the Dirac cone is shifted to lower energy, i.e., the graphene sheet is n-doped. Cs decouples the graphene sheet, while the spin polarization of Ni(111) does not extend through the intercalated atoms to the graphene sheet, for which we find virtually spin-degeneracy. In order to employ graphene in electronic applications, one requires a finite band gap. We engineer a band gap in metallic bilayer graphene by substitutional B and/or N doping. Specifically, the introduction of B-N pairs into bilayer graphene can be used to create a band gap that is stable against thermal fluctuations at room temperature. Introduction of B-N pairs into B and/or N doped bilayer graphene likewise hardly modifies the band dispersions, however, the size of the band gap is effectively tuned. We also study the influence of terrace edges on the electronic properties of graphene, considering bare edges and H, F, Cl, NH2 terminations. Periodic structural reconstruction is observed for the Cl and NH2 edge terminations due to interaction between the terminating atoms/groups. We observe that Cl edge termination p-dopes the terraces, while NH2 edge termination results in n-doping.