The long-term collaboration between NPL, Chalmers and Graphensic, has resulted in a big advance in graphene samples. Epitaxial graphene (epigraphene) has been grown on silicon carbide and has better performance at higher temperatures and lower magnetic field than was previously possible. In practical terms, it has also removed the difficult process of fine-tuning the carrier density and means the ‘table-top’ system can be warmed up and cooled back down and the plateau stays where it is set with no user intervention.
NPL, Chalmers and the national metrology institute of Sweden (RISE) have demonstrated the metrological quality and stability of these types of devices for up to two years.
Sergey Kubatkin, professor at the Quantum Device Physics Laboratory at MC2, is one of the researchers involved in the project:
"With the new definitions of certain units within the International System of Units (SI) coming into effect since 20 May 2019, the epigraphene-based quantum Hall devices are used to disseminate not only the electrical units, but also other standards relying on electrical measurements, such as the unit of mass, the kilogram," he says in a press release from NPL.
JT Janssen, chief scientist at NPL, explains the importance of this work:
"One of the aspirations of quantum metrology is to deliver primary standards directly to end-users. Epitaxial graphene has enabled us to demonstrate significantly shorter traceability chains and more accurate measurements, with a more accurate and compact piece of equipment. This is a step change in capability and an exciting development," he says.
The project was in part funded by Chalmers innovationskontor, and is one of the impact cases at MC2 during 2019.
Text: NPL and Michael Nystås