The article shows how the dynamic mapping of surface potential (SP) measured by Kelvin probe force microscopy (KPFM) in combination with calculation by a diffusion-like equation and the theory based on the Brunauer-Emmett-Teller (BET) model of water condensation and electron hopping can provide the information concerning the resistivity of low conductive surfaces and their water coverage. This is enabled by a study of charge transport between isolated and grounded graphene sheets on a silicon dioxide surface at different relative humidity (RH) with regard to the use of graphene in ambient electronic circuits and especially in sensors. In the experimental part, the chemical vapor-deposited graphene is precisely patterned by the mechanical atomic force microscopy (AFM) lithography and the charge transport is studied through a surface potential evolution measured by KPFM. In the computational part, a quantitative model based on solving the diffusion-like equation for the charge transport is used to fit the experimental data and thus to find the SiO2 surface resistivity ranging from 107 to 1010 Ω and exponentially decreasing with the RH increase. Such a behavior is explained using the formation of water layers predicted by the BET adsorption theory and electron-hopping theory that for the SiO2 surface patterned by AFM predicts a high water coverage even at low RHs.

Central European Institute of Technology Brno University of Technology Purkyňova 123 612 00 Brno Czech Republic

Department of Physics and Materials Engineering Faculty of Technology Tomas Bata University in Zlín Vavrečkova 275 760 01 Zlín Czech Republic

Department of Thin Films and Nanostructures Institute of Physics The Czech Academy of Sciences Cukrovarnická 10 112 162 00 Praha 6 Czech Republic

Institute of Physical Engineering Brno University of Technology Technická 2 616 69 Brno Czech Republic

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