Scientists have developed a new method of characterizing graphene without using destructive electrical contacts, enabling them to study the resistance and quantum capacitance of graphene and other two-dimensional materials. Researchers from the Swiss Institute of Nanoscience and the Department of Physics at the University of Basel reported their findings in the journal Physical Review Application.
Graphene consists of a single layer of carbon atoms. It is transparent, harder than diamond, stronger than steel, more flexible, and more conductive than copper. Since graphene was first isolated in 2004, scientists around the world have been studying its properties and possible applications for ultra-thin materials. There are other two-dimensional materials with similar promising applications; however, their electronic structure research is scarce.
No electrical contact required
Electrical contacts are often used to characterize the electronic properties of graphene and other two-dimensional materials. However, these can significantly change the properties of the material. The team of Professor Christian Schönenberger from the Swiss Institute of Nanoscience and the Department of Physics at the University of Basel has now developed a new method to study these properties without using contact.
To this end, scientists embedded graphene in boron nitride, an isolator, placed it on a superconductor, and coupled it with a microwave resonator. Both the resistance and quantum capacitance of graphene affect the figure of merit and resonance frequency of the resonator. Although these signals are very weak, they can be captured using a superconducting resonator.
By comparing the microwave characteristics of resonators with and without graphene packages, scientists can determine resistance and quantum capacitance. "These parameters are very important in determining the exact nature of graphene and the limiting factors in its application," explains Simon Zihlmann, a doctoral student in the Schönenberger Group.
Also suitable for other 2D materials
During the development of this method, boron nitride-encapsulated graphene was used as a prototype material. Graphene integrated into other materials can be studied in the same way. In addition, other two-dimensional materials can be characterized without the use of electrical contacts; for example, semiconductor molybdenum disulfide, which has applications in solar cells and optics.