RF Transport Electromagnetic Properties of CVD Graphene from DC to 110 MHz

TL;DR

This study measures the RF electromagnetic properties of CVD graphene from DC to 110 MHz, revealing substrate effects and intrinsic resistance, and introduces a model for understanding its frequency response.

Contribution

It presents the first phenomenological lumped-parameter model for RF graphene impedance, demonstrating the frequency-independent intrinsic resistance of graphene channels.

Findings

Intrinsic graphene resistance is frequency-independent up to 110 MHz.

Substrate parasitic effects dominate at frequencies above 1 MHz.

The RF 4TP method aligns well with DC measurements for graphene resistance.

Abstract

We report measurement of the radio-frequency (RF) transport electromagnetic properties of chemical vapour deposition (CVD) graphene over the DC to 110 MHz frequency range at room temperature. Graphene on Si/SiO2 substrate was mounted in a shielded four terminal-pair (4TP) adaptor which enabled direct connection to a calibrated precision impedance analyser for measurements. Good agreement is observed for the DC four-probe resistance and the 4TP resistance at 40 Hz, both yielding R ~ 104 {\Omega}. In general the apparent graphene channel electromagnetic properties are found to be strongly influenced by the substrate parasitic capacitance and resistance, particularly for high-frequencies f > 1 MHz. A phenomenological lumped-parameter equivalent circuit model is presented which matches the frequency response of the graphene 4TP impedance device over approximately seven decades of the frequency range of the applied transport alternating current. Based on this model, it is shown for the first time, that the intrinsic graphene channel resistance of the 4TP device is frequency-independent (i.e. dissipationless) with RG ~ 105 {\Omega} or sheet resistance of approximately 182 {\Omega} / sq. The parasitic substrate impedance of the device is found shunt RG with RP ~ 2.2 {\Omega} in series with CP ~ 600 pF. These results suggest that our new RF 4TP method is in good agreement with the conventional DC four-probe method for measuring the intrinsic sheet resistance of single-atom thick materials and could potentially open up new applications in RF electronics, AC quantum Hall effect metrology and sensors based on graphene 4TP devices operating over broad range of frequencies.