Contactless microwave characterization of encapsulated graphene p-n junctions to appear in Physical Review Applied, see:

Graphene and other 2D materials play a major role in research aiming to go beyond CMOS technology and current computation paradigms. In general electrical contacts to these materials are needed to perform standard low frequency conductance measurements. However, the electrical contacts strongly influence the material properties. Therefore, the determination of the intrinsic material properties is challenging.
Vishal Ranjan, Simon Zihlmann, Peter Makk and Christian Schönenberger of the University of Basel and the Swiss Nanoscience Institute together with their collaborators K. Watanabe and T. Taniguchi from the National Institute for Material Science at Tsukuba Japan developed a novel technique which enables characterizations of these materials without the need for electrical contacts. This relies on a capacitive coupling of the material to a high quality microwave resonator. In this work, they have used this method to investigate the properties of graphene pn-junctions. Simultaneous determination of both the resistance and the quantum capacitance of the graphene sheet is achieved. Hence, information of the band structure and the scattering mechanisms is obtained with a single measurement. This technique is not only limited to graphene but also applicable to further 2D materials and thus enables the study of more exotic materials.


Contactless admittance measurement; paper accepted!