Regensburg 2013 – scientific programme

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O: Fachverband Oberflächenphysik

O 57: Graphene: SiC Substrates and Intercalation (jointly with HL, MA and TT)

O 57.2: Talk

Wednesday, March 13, 2013, 16:15–16:30, H17

Transport properties of epitaxially grown graphene nanostructures — •Jens Baringhaus, Frederik Edler, Herbert Pfnür, and Christoph Tegenkamp — Institut für Festkörperphysik, Leibniz Universität Hannover, 30167 Hannover, Germany

The patterning of graphene into small stripes, the so called graphene nanoribbons, is an essential task for the development of future graphene based electronic devices. For such ribbons with a well-ordered edge geometry the presence of one-dimensional edge states has been predicted. The fabrication of these well-defined structures requires the avoidance of any damaging post-processing. To overcome this obstacle we use a selective graphitization process on SiC-mesa structures, producing monolayer graphene nanoribbons of 40 nm to 100 nm in width and of several micrometers in length. The local electronic properties of the ribbons are investigated by means of a 4-tip STM. The self-assembled graphene nanoribbbons show metallic behavior and can be clearly distinguished from the non-metallic substrate. Conductances close to G₀=e²/h are observed for a wide temperature range from 30 K up to room temperature. Description within the Landauer formalism is possible assuming ballistic transport dominated by a single ballistic channel. This is a strong indication for spin-polarized transport through the edge-states of the ribbons. These edge states also show up in scanning tunneling spectra. At higher temperatures the conductance increases due to the occupation of the next subband. Remarkably all investigated ribbons exhibit very large mean free paths up to 15 µ m.