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HL: Fachverband Halbleiterphysik

HL 50: Graphene and Carbon Nanotubes

HL 50.6: Vortrag

Donnerstag, 25. März 2010, 11:00–11:15, H15

Hysteresis in the Field Effect of Bilayer Graphene at Low Temperatures — •Patrick Barthold, Thomas Lüdtke, and Rolf J. Haug — Institut für Festkörperphysik, Leibniz Universität Hannover, Appelstr. 2, 30167 Hannover, Germany

We present transport measurements on single crystal bilayer graphene at low temperatures down to 1.5 K. In the field effect a strong hysteresis is observed. The bilayer graphene is deposited via micromechanical cleavage on top of a 265 nm SiO₂/Si substrate. Using standard e-beam lithography the device is structured and leads are evaporated to the device (Ti/Au). As the field effect is measured at T=1.5 K in a four-terminal setup the neutrality point varies in dependence of the direction the back-gate voltage is swept. This splitting in the neutrality points (hysteresis) changes with different sweeping rates. At the lowest rate (6.6 mV/s) the splitting is almost zero, whereas it rises with faster rates. By applying a perpendicular magnetic field to the device the hysteresis changes dramatically. We attribute this behaviour to molecular adsorbates which act as charge traps.