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O: Fachverband Oberflächenphysik
O 15: Focused Session: Epitaxial Graphene II
O 15.3: Vortrag
Montag, 23. März 2009, 15:45–16:00, SCH 251
An ab initio study of graphene buffer layers on SiC — •Stephan Hensel, Michel Bockstedte, and Oleg Pankratov — Lst. Theoretische Festkörperphysik, Universität Erlangen-Nürnberg, Staudststr 7B2, 91058 Erlangen
Silicon Carbide enables the growth of few layer graphene by thermal sublimation of silicon. Graphene layers with disparate properties are formed on (0001) and (0001) surfaces.1−4 On (0001)-SiC a 6√3×6√3 buffer layer forms, which serves as a template for subsequent alined layers.1,2 On (0001)-SiC, in contrast, carbon layers are mutually rotated being practically decoupled from each other and hence possessing individual Dirac spectra.3 The distinction manifests itself in the presence (Si-termination) or absence (C-termination) of covalent graphene-SiC bonding in XPS.4 With ab initio methods we analyzed the bonding of graphene on SiC (0001) and (0001) surfaces. We consider a tractable 5×5 model that allows for low strain and the turbostratic registry of graphene. The calculations demonstrate clearly the distinct bonding features on the two surfaces. While covalent graphene-substrate bonds are present for almost all atoms on the Si-terminated surface, such bonding is absent for as much as 50% of the carbon atoms on the C-terminated face.
[1] T. Ohta et al, Science 313, 951 (2006)
[2] C. Riedl et al. Phys. Rev. B 76, 245406 (2007).
[3] J. Hass et al, Phys. Rev. Lett. 100,125504 (2008).
[4] K.V. Emtsev et al, Phys. Rev. B 77, 155303 (2008).