A method is established to reliably determine surface conductance of single-layer or multi-layer atomically thin nano-carbon graphene structures. These can be synthesized by chemical vapor deposition (CVD), epitaxial growth on silicon carbide (SiC), obtained from reduced graphene oxide (rGO) or mechanically exfoliated from graphite. The measurements are made in an air filled standard WR-90 rectangular waveguide configuration at one of the resonant frequency modes, typically at 7 GHz. Surface conductance measurement involves monitoring a change in the quality factor of the cavity as the specimen is progressively inserted into the cavity in quantitative correlation with the specimen surface area. The specimen consists of a nano-carbon-layer supported on a low loss dielectric substrate. The thickness of the conducting nano-carbon layer does not need to be explicitly known, but it is assumed that the lateral dimension is uniform over the specimen area. The non-contact surface conductance measurements are illustrated for CVD graphene and epitaxial graphene. We compare these non-contact results with longitudinal resistance of mono graphene layers formed by sublimation of Si on SiC (0001) wafers.
graphene, surface conductance, microwave cavity