Berlin 2012 – scientific programme

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O: Fachverband Oberflächenphysik

O 34: Poster Session I (Graphene; Plasmonics and nanooptics; Coherence and coherent control in nanophotonics and plasmonics)

O 34.6: Poster

Tuesday, March 27, 2012, 18:15–21:45, Poster E

Local transport measurements in graphene and graphene nanostructures — •Frederik Edler, Jens Baringhaus, Thomas Langer, Herbert Pfnür, and Christoph Tegenkamp — Institut für Festkörperphysik, Leibniz Universität Hannover, Abteilung Atomare und Molekulare Strukturen, Appelstrasse 2, 30167 Hannover, Germany

Graphene exhibits interesting transport signatures. The non-vanishing conductivity in neutral graphene was believed to be a signature of a ballistic system. However, diffusive transport theory including long range ordered defects reveal similar conductance values. Therefore, the control of the structure is important in order to interpret transport data, affected by in impurities, defects, or finite size effects, correctly. We have studied the morphology and the resistivity of graphene and graphene nanostructures by means of a 4-tip STM SEM system.
Due to inhomogeneous growth and the residual influence of substrate, the sheet resistance for monolayer graphene, grown on SiC(0001) and SiC(0001) substrates, was around 40-50 kΩ / . After further graphitization it decreased to 8 kΩ / . Graphene bilayers on SiC(0001) reveal values close to those reported for exfoliated graphene. Besides 2d graphene, uniaxial graphene nanoribbon structures (width ≈ 100 nm), grown by using appropriate SiC-MESA structures, have been studied. The resistances measured on them were found to be significantly lower and are almost independent on the contact separation, as expected for graphene ribbons with robust edge channels.