Berlin 2012 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 41: Graphene III

O 41.8: Vortrag

Mittwoch, 28. März 2012, 12:15–12:30, MA 041

DFT study of the electronic structure of graphene/Ag(111)/Re(0001) — •Jörg Doppler, Florian Mittendorfer, and Josef Redinger — Inst. of Applied Physics, Vienna University of Technology, Vienna, Austria

Data from ARPES experiments on graphene/Re and graphene/Ag/Re(0001), which features an additional intercalated Ag monolayer, demonstrate that the strong interaction of Gr/Re is significantly lowered as soon as Ag is introduced. It is also found that the Ag atoms grow epitactically, and we have evidence of a hybridization of the Ag bands with graphene’s π-state. We study the electronic structure of Gr/Ag(111)/Re(0001) by means of numerical ab-initio DFT calculations employing the program VASP. The properties of gr/Ag/Re were determined in a simplified approach by examining a (1x1) cell for the two equilibrium lattice constants of Re and Gr, i.e. either stretching Gr or compressing the underlying Ag/Re substrate, respectively. Different interface models and graphene-substrate distances were tested to determine the energetically most favourable placement of the carbon atoms relative to the substrate surface, yielding the top-fcc arrangement as the structure featuring the lowest energy. Due to interaction with the Ag/Re substrate, the electronic structure of graphene is modified, showing qualitative agreement with above mentioned ARPES experiments. We observe a downward shift of the Dirac point with respect to the Fermi energy as well as hybridization of the graphene π-band with the Ag d-bands. The strength of both phenomena depends on the graphene-substrate distance.