Gregory, A P; Hao, L; Klein, N*; Gallop, J C; Mattevi, C*; Shaforost, O*; Lees, K; Clarke, R N (2014) Spatially resolved electrical characterisation of graphene layers by an evanescent field microwave microscope. Physica E, 56. pp. 431-434.

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Abstract

An evanescent field microwave microscope has been developed at the National Physical Laboratory. This instrument has multiple applications. In this paper we describe basic operation of the microscope and show recent measurements on graphene samples produced at Imperial College. The microscope obtains images by raster scanning of a wire probe in `contact mode'. Of particular interest to the graphene community is the possibility of being able to scan over large areas (up to 4x4 mm), and to be able to measure surface resistance without a requirement for metal contacts. As an ultrathin semimetal, a graphene layer being placed in the evanescent field of the probe is expected to behave like a lossy dielectric material, its microwave loss tangent is proportional to its conductivity. Employing a high Q dual mode re-entrant cavity as host resonator and a spherical metal probe of 180 micrometer diameter, we found that spatial variations of the conductivity of graphene can be clearly resolved.

Item Type:	Article
Keywords:	graphene, near-field scanning microwave microscope, surface impedance
Subjects:	Electromagnetics Electromagnetics > RF and Microwave
Identification number/DOI:	10.1016/j.physe.2012.10.006
Last Modified:	02 Feb 2018 13:13
URI:	http://eprintspublications.npl.co.uk/id/eprint/6129

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