12 NovPhD DissertationProximity Mechanisms in Graphene: Insights from First-Principles Calculations
Proximity Mechanisms in Graphene: Insights from First-Principles Calculations
  • Maha Alattas
  • Ph.D. Candidate supervised by Prof. Udo Schwingenschloegl
  • Monday, November 12, 2018
  • 08:00 AM - 10:30 AM
  • Ibn Al Haytham Building (Bldg. 2), Room 5220
2018-11-12T08:002018-11-12T10:30Asia/RiyadhProximity Mechanisms in Graphene: Insights from First-Principles CalculationsIbn Al Haytham Building (Bldg. 2), Room 5220Mazen E. Mero

ABSTRACT: One of the challenges in graphene fabrication is the production of large scale, high quality sheets. We study a possible approach to achieve quasi-freestanding graphene on a substrate by the intercalation of alkali metal atoms, therefore Cs intercalation between graphene and Ni(111) is investigated. It is known that direct contact between graphene and Ni(111) perturbs the Dirac states. We confirm that 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, on the other hand, 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 efficiently employ graphene in electronic applications, one requires a finite band gap. We engineer a band gap in a the 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 in the presence of B-N pairs. We also study the influence of terrace edges on the electronic properties of graphene considering bare edges and H, F, Cl, NH_2 terminations. Periodic structural reconstruction is observed for the Cl and NH_2 edge terminations due to interaction between the terminating atoms/groups. We observe that Cl edge termination p-dopes the terraces, while NH_2 edge termination results in n-doping.

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  • Mazen E. Mero

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