Berlin 2018 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 43: Graphene: Electronic Properties, Structure and Substrate Interaction II (joint session O/TT)
TT 43.1: Hauptvortrag
Dienstag, 13. März 2018, 10:30–11:00, MA 043
Inside graphene devices — •Clemens Winkelmann1, Sayanti Samaddar1, Alessandro De Cecco1, Hervé Courtois1, Indra Yudhistira2, Shaffique Adam2, Vladimir Prudkovskiy1,3, Claire Berger1,3, and Walt de Heer3 — 1Univ. Grenoble Alpes / France — 2NUS / Singapore — 3Georgia Inst. of Technol. / USA
The electronic transport properties of devices are governed by microscopic physics which can often only be inferred indirectly from the former. By combining in situ transport and scanning probe experiments in graphene-based devices, we directly test the microscopic pictures used for predicting macroscopic transport properties.
The first part focusses on the charge puddles in diffusive graphene on a disordered dielectric substrate. Because of the linear dispersion relation in monolayer graphene, the puddles are predicted to grow near charge neutrality, a markedly distinct property from conventional two-dimensional electron gases. Using STM/STS on a gated single mesoscopic graphene device, we observe the puddles' growth as the Fermi level approaches the Dirac point. Self-consistent screening theory provides a unified description of both the macroscopic transport properties and the microscopically observed charge disorder.
The second part extends the above technique to a system with very little disorder, namely graphene nanoribbons grown on the sidewalls of steps of a SiC substrate. By performing STM (and the related scanning tunneling potentiometry technique) on such nanoribbons driven out of equilibrium, we gain novel insights into the extraordinary transport properties of graphene nanoribbons.