Non-contact method for measurement of the microwave conductivity of graphene

TL;DR

This paper introduces a rapid, non-contact microwave resonator technique for measuring the conductivity and sheet resistance of graphene, applicable to various sample types with high sensitivity and dynamic range.

Contribution

The study presents a novel microwave dielectric resonator method for non-contact, accurate measurement of graphene's microwave conductivity and sheet resistance, applicable to different growth methods.

Findings

Higher conductivity in epitaxially grown graphene on SiC.

Method sensitive to impurities and imperfections.

Applicable to monolayer and few-layer graphene samples.

Abstract

We report a non-contact method for conductivity and sheet resistance measurements of graphene samples using a high Q microwave dielectric resonator perturbation technique, with the aim of fast and accurate measurement of microwave conductivity and sheet resistance of monolayer and few layers graphene samples. The dynamic range of the microwave conductivity measurements makes this technique sensitive to a wide variety of imperfections and impurities and can provide a rapid non-contacting characterisation method. Typically the graphene samples are supported on a low-loss dielectric substrate, such as quartz, sapphire or SiC. This substrate is suspended in the near-field region of a small high Q sapphire puck microwave resonator. The presence of the graphene perturbs both centre frequency and Q value of the microwave resonator. The measured data may be interpreted in terms of the real and imaginary components of the permittivity, and by calculation, the conductivity and sheet resistance of the graphene. The method has great sensitivity and dynamic range. Results are reported for graphene samples grown by three different methods: reduced graphene oxide (GO), chemical vapour deposition (CVD) and graphene grown epitaxially on SiC. The latter method produces much higher conductivity values than the others.