▎ 摘　　要

We study transport properties of a locally gated graphene device. The samples are made by exfoliation of natural graphite onto a SiO(2) substrate such that single layers of graphene can be contacted and the potential can be tuned by applying a voltage to the SiO(2). Additional top gates are fabricated to control the carrier concentration locally. In doing so we find that induced electrons and holes are distributed in two 2D systems that are decoupled. The characteristic of the Shubnikov-de Haas oscillations shows that these systems behave like two monolayers of graphene, which has to be decoupled due to its magneotransport characteristic. (C) 2009 Elsevier B.V. All rights reserved.