Regensburg 2013 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 46: Graphene - SiC Substrates and Intercalation (jointly with DS, HL, MA, and O)

TT 46.3: Talk

Wednesday, March 13, 2013, 16:30–16:45, H17

Local investigation of transport properties and morphology of epitaxially grown 2d graphene — •Frederik Edler, Jens Baringhaus, Herbert Pfnür, and Christoph Tegenkamp — Institut für Festkörperphysik, Leibniz Universität Hannover, Appelstraße 2, 30167 Hannover, Germany

Graphene has a peculiar band structure and special transport properties. The transport is strongly affected by imperfections of the graphene films, e.g atomic steps and impurities located at the interface between graphene and its support. A reliable control of these parameters is possible by epitaxial grown graphene on SiC. To characterize the epitaxial growth and correlate the structure with transport properties, the sheet resistance of graphene grown on SiC(0001) and SiC(0001) have been studied via a 4-tip STM/SEM system. The SEM allows precise positioning of feedback controlled STM tips, enabling transport measurements on a nm-scale. While STM is used to characterize atomic size defect structures, step-bunches and nano-inhomogeneities can be identified in SEM. Sheet resistances were found to be independent from probe spacing indicating a 2d transport behavior but highly depending on ex-situ processing steps. Further in-situ annealing led to sheet resistances around 6−8 k Ω /. These values can be explained by diffusive transport theory [1] and correlate with the concentration of the nano-inhomogeneities. Structural defects induce a mobility gap as deduced from temperature-dependent transport measurements. The sheet resistance increased by a factor of three for elastically bend graphene layers across SiC step-bunches. [1] Adam et al., PNAS, 104, 18392 (2007)