Berlin 2015 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 107: Graphene: Electronic Structure (jointly with O, HL)

TT 107.6: Talk

Thursday, March 19, 2015, 16:15–16:30, MA 041

From ribbons to constrictions: STM lithography on ballistic sidewall graphene nanoribbons — •Jens Baringhaus¹, Mikkel Settnes², and Christoph Tegenkamp¹ — ¹Leibniz Universität Hannover, Institut für Festkörperphysik, 30167 Hannover, Germany — ²Technical University of Denmark, DTU Nanotech, Center for Nanostructured Graphene (CNG), 2800 Kgs. Lyngby, Denmark

The selective graphene growth on the sidewalls of SiC mesa structures produces well-ordered graphene nanoribbons (GNR) with exceptional transport properties. Using a 4-tip STM, a probe spacing and temperature independent conductance of e²/h is found, indicating single channel ballistic transport even at room temperature [1]. The robustness of the ballistic channel makes these GNR ideal templates for morphological alterations. For this purpose, one of the STM tips is used for local lithography. Careful control over the feedback parameters and the bias voltage allows to either fully cut the ribbon or to create narrow, a few nm wide constrictions. Every STM lithography step is monitored directly by local transport. After a full cut, the transport characteristics of the sidewall GNR are completely destroyed. In contrast, in narrow constrictions the ballistic channel is preserved, but only present at bias voltages exceeding 10 mV. Additionally, localized currents manifest as resonances in the IV curves at bias voltages of about 8 mV. Using a standard tight binding and recursive Green’s function approach, the resonances are found to be robust against temperature as well as different types of disorder, e.g. Anderson or edge disorder.
Baringhaus et al., Nature 506, 349 (2014)