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HL: Fachverband Halbleiterphysik

HL 53: Transport properties

HL 53.6: Talk

Friday, March 27, 2009, 11:30–11:45, POT 151

Tunable Graphene System with Two Decoupled Monolayers — •Hennrik Schmidt, Thomas Lüdtke, Patrick Barthold, and Rolf J. Haug — Institut für Festkörperphysik, Leibniz Universität Hannover, D-30167 Hannover, Germany

Atomically thin sheets of carbon, graphene, can be used as current-carrying components in field-effect transistors. Using micromechanical cleavage of natural graphite, flakes of different thickness are deposited on top of a silicon wafer with a 330 nm thick silicon oxide, including also folded samples. This folding leads to a misorientation and thereby to decoupling of the two stacked layers.
We present measurements on such two layer systems consisting of decoupled monolayers [1]. To distinguish this sample from monolayer and single cystal bilayer graphene, magnetotransport measurements are carried out with temperatures down to 1.5 Kelvin. A backgate voltage between -70 V and 70 V is used to tune the carrier concentration and type. Applying magnetic fields up to 13 Tesla, the longitudinal resistance shows two sets of Shubnikov-de Haas oscillations with a Berry’s phase of π for both oscillations, verifying a system of stacked monolayers. From the period of theses oscillations, the charge carrier densities are obtained, showing different values for each layer due to screening effects.
H. Schmidt, T. Lüdtke, P. Barthold, E. McCann, V. I. Fal’ko, and R. J. Haug, Appl. Phys. Lett. 93, 172108 (2008)