Electric field doping of few-layer graphene

We report on magneto-transport and quantum Hall effect measurements in a few-layer graphene sample in magnetic fields up to 55T applied perpendicular to the layers. Few-layer graphene systems consist of several planes of carbon atoms and exhibit complex electronic band structures. Regarding their transport properties, they are natural candidates to study the cross over from 3D graphite to 2D graphene. The sample, obtained by micro-mechanical exfoliation of graphite, displays a p-type conductivity that was tuned by the application of a back gate voltage. The Hall and longitudinal resistances were simultaneously recorded and analyzed. We find evidences of two regimes of charge carrier dynamics driven by massive and Dirac fermions, respectively, depending on the gate voltage. The Dirac fermion signatures are observed from 2 to 120 K. (C) 2009 Elsevier B.V. All rights reserved.