Berlin 2012 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 22: Graphene: Structure and Theory II
HL 22.7: Vortrag
Montag, 26. März 2012, 18:45–19:00, EW 201
Graphene on Different SiC Polytypes — Oleg Pankratov, •Stephan Hensel, and Paul Götzfried — Theoretische Festkörperphysik, Universität Erlangen, Staudtstr. 7B2, 91058 Erlangen
Epitaxial graphene grows on different SiC polytypes, yet the influence of the substrate polytype on graphene Dirac spectrum has not been systematically studied. We address this question with ab initio calculations, comparing the electronic structure of a graphene epilayer on polytypes with different hexagonality, various terminations and buffer/epilayer stackings within the (√3×√3)R30 interface model. We find the Dirac point alignment relative to the valence band substantially varies depending on polytype, but the Fermi level pinning and hence the doping of the epilayer stay the same. For the most relevant case of a buffer/epilayer Bernal stacking (Si-face) the Dirac cone splits by εg < 40 meV, whereas it remains intact for the AA-stack. This can be understood within the analytical symmetry-based model, which allows to establish a direct connection between εg and the buffer/epilayer interaction potential.