Abstract
We have performed scanning gate microscopy (SGM) on graphene field effect transistors(GFET) using a biased metallic nanowire coated with a dielectric layer as a contact modetip and local top gate. Electrical transport through graphene at various back gate voltagesis monitored as a function of tip voltage and tip position. Near the Dirac point, theresponse of graphene resistance to the tip voltage shows significant variation with tipposition, and SGM imaging displays mesoscopic domains of electron-doped and hole-dopedregions. Our measurements reveal substantial spatial fluctuation in the carrier density ingraphene due to extrinsic local doping from sources such as metal contacts, grapheneedges, structural defects and resist residues. Our scanning gate measurements alsodemonstrate graphene’s excellent capability to sense the local electric field and charges.
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