Dresden 2014 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 76: Graphene: Electronic properties (organized by O)

HL 76.3: Talk

Wednesday, April 2, 2014, 16:30–16:45, WIL C107

Exceptional ballistic transport in epitaxial graphene nanoribbons — Jens Baringhaus¹, Frederik Edler¹, Claire Berger², Walter A. de Heer², and •Christoph Tegenkamp¹ — ¹Leibniz Universität Hannover, Institut für Festkörperphysik, 30167 Hannover, Germany — ²Georgia Institute of Technology, Atlanta, Georgia 30332-0430, USA

The patterning of graphene into graphene nanoribbons is an essential task for the development of graphene based devices. For such ribbons with a well-ordered edge geometry the presence of one-dimensional edge states has been predicted. We use a selective graphitization process on SiC-mesa structures to produce graphene nanoribbons with a width of 40 nm. The local electronic properties of the ribbons are investigated by means of a 4-tip STM. In combination with a SEM, the precise positioning of all four tips on the nanometer range is possible to perform local transport measurements. Additionally, local tunneling spectroscopy reveals characteristic features of ferromagnetic zig-zag graphene nanoribbons. Transport experiments carried out on the very same ribbon show a conductance close to e²/h for a wide temperature range from 30 K up to room temperature and probe spacings between 1 µm and 10 µ m. Description within the Landauer formalism is possible assuming ballistic transport dominated by a single channel. Transport in the second zeroth subband is only detectable for probe spacings smaller than 1 µ m due to the short localization length of carriers in this subband manifesting in the increase of the conductance to 2 e²/h at probe spacings below 200 nm.