title: Scanning gate microscopy on graphene: charge inhomogeneity and extrinsic doping.
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 mode tip and local top gate. Electrical transport through graphene at various back gate voltages is monitored as a function of tip voltage and tip position. Near the Dirac point, the response of graphene resistance to the tip voltage shows significant variation with tip position, and SGM imaging displays mesoscopic domains of electron-doped and hole-doped regions. Our measurements reveal substantial spatial fluctuation in the carrier density in graphene due to extrinsic local doping from sources such as metal contacts, graphene edges, structural defects and resist residues. Our scanning gate measurements also demonstrate graphene's excellent capability to sense the local electric field and charges.
authors.affiliation: Department of Physics, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: Romaneh
authors.initials: R
authors.lastname: Jalilian
authors.forename: Luis A
authors.initials: LA
authors.lastname: Jauregui
authors.forename: Gabriel
authors.initials: G
authors.lastname: Lopez
authors.forename: Jifa
authors.initials: J
authors.lastname: Tian
authors.forename: Caleb
authors.initials: C
authors.lastname: Roecker
authors.forename: Mehdi M
authors.initials: MM
authors.lastname: Yazdanpanah
authors.forename: Robert W
authors.initials: RW
authors.lastname: Cohn
authors.forename: Igor
authors.initials: I
authors.lastname: Jovanovic
authors.forename: Yong P
authors.initials: YP
authors.lastname: Chen