Regensburg 2010 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 50: Graphene and Carbon Nanotubes
HL 50.1: Vortrag
Donnerstag, 25. März 2010, 09:30–09:45, H15
Electronic properties of twisted graphene monolayers — •Hennrik Schmidt, Patrick Barthold, Thomas Lüdtke, and Rolf J. Haug — Institut für Festkörperphysik, Leibniz Universität Hannover, D-30167 Hannover, Germany
We investigate the transport properties of two stacked graphene monolayers with a rotational stacking fault in respect to Bernal stacking. Using micromechanical cleavage of graphite as preparation methode, flakes of different thickness, also including folded samples, are deposited on top of a silicon wafer with a 330 nm thick silicon oxide. This folded monolayer graphene forms a system of two very closely spaced layers, decoupled due to the misorientation. Magneto–transport measurements on this decoupled monolayers conducting in parallel are performed variing perpendicular applied magnetic field, backgate voltage and temperature. From the Shubnikov–de Haas oscillations, carrier densities are obtained, being different for the two layers due to screening. Mobilities and scattering times are calculated for both layers and exhibit significantly higher values in the top layer, indicating weaker substrate influence. From the temperature dependence of the Shubnikov–de Haas oscillations, the cyclotron masses are obtained, yielding higher values than for a single monolayer. These masses correspond to reduced Fermi velocities of down to 0.66· 106 m/s, being consistent with theory.
[1] H. Schmidt, T. Lüdtke, P. Barthold, E. McCann, V. I. Fal’ko, and R. J. Haug, Appl. Phys. Lett. 93, 172108 (2008)