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O: Fachverband Oberflächenphysik

O 8: Focused Session: Epitaxial Graphene I

O 8.4: Vortrag

Montag, 23. März 2009, 12:15–12:30, SCH 251

Electronic excitations in epitaxial graphene layers grown on SiC(0001) — •Thomas Langer^1,2, Herbert Pfnür¹, Christoph Tegenkamp¹, Hans Werner Schumacher², and Uwe Siegner² — ¹Institut für Festkörperphysik, Leibniz Universität Hannover, Appelstrasse 2, D-30167 Hannover, Germany — ²Physikalisch-Technische Bundesanstalt, Bundesallee 100, D-38116 Braunschweig, Germany

Transport measurements on epitaxial graphene require flat and large-scale graphene layers to apply electrical contacts. For this purpose growth of graphene on SiC(0001) has been studied with spot profile analysis low energy electron diffraction (SPA-LEED) and has been controlled and correlated in addition with X-ray photoelectron spectroscopy (XPS). The lateral (H(S)-analysis) and vertical (G(S)-analysis) roughness of different prepared SiC samples has been investigated as a function of graphene layers. Only the buffer and the first graphene layer show almost no additional roughening within the transfer width (200 nm) after graphitization process. The influence of interfaces on the loss function of epitaxial graphene layers has been studied further by means of electron energy loss spectroscopy (EELS). Electronic transitions and plasmon losses are sensitive to the interface. The collective in-plane excitations show a characteristic blueshift after graphitization, while single electron transitions with dipole moments along the surface normal are suppressed for the buffer layer. These characteristics can be used to distinguish between the buffer layer and intact graphene layers on top.