Graphene oxide, a chemically modified graphene, has been attracting wide attention because of promising adaptability to a wide variety of applications. However, the properties of graphene oxide itself are not known well. Using a conductive cantilever, we observed a current image of graphene oxide nanosheets of various thicknesses. Currentvoltage characteristics were found to reflect the local conductivity normal to the nanosheets. Under high electric fields, the conduction was well described in terms of PooleFrenkel emission mechanism. The fitting of IV curves to the PooleFrenkel model provides information on dielectric properties, and the relative permittivity of graphene oxide was found to be 4.8 ± 0.8.
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