Electrical measurements on graphene
Graphene exhibits unique electrical properties as a result of its unusual linear band structure. The mobility of charge carriers in graphene is higher at room temperature than that of silver (previously the highest conductivity material known to man). Graphene also has a high thermal conductivity, comparable to diamond, and is transparent, flexible and very strong.
These properties have attracted a lot of interest in graphene from the electronics industry as a possible replacement for silicon in transistors or ITO (indium tin oxide) in touch screen displays. Other applications include transparent electrodes in solar cells or electrodes for super capacitors. Furthermore, graphene could be the base material for completely new types of information technology based on the spin of an electron rather than its charge. For more information, please see the graphene roadmap published in Nature.
Graphene is also very interesting for measurement science because it shows a very strong quantum Hall effect. So strong in fact that it can even be observed at room temperature in very pure materials. NPL has made some of the most accurate measurements ever of this effect and demonstrated that graphene can be used as a quantum standard for electrical resistance. NPL scientists demonstrated that it is possible to make a quantum standard for electrical current from graphene by patterning a sequence of small quantum dots and manipulating these with fast RF signals.
At NPL, we study the physics behind these quantum effects in an effort to, firstly, improve the accuracy and usability and, secondly, discover new effects that might be of importance to metrology and industry. We try to link the measured electrical properties to the morphology and chemical characteristics, which NPL also measures. A key aspect of this research is close collaboration with academic groups in the UK and across the world in order to bring the best scientists together and pool the available technical resources.