The main promise of quantum metrology is to deliver turnkey primary standards directly to end-users in industry and academia, thereby enabling far more accurate products. A bottleneck in the realisation of one such primary standard namely for electrical resistance, has up until now been the quantum Hall effect device.
For some time the quantum Hall effect devices used by national metrology institutes have been relying on conventional semiconductor two-dimensional electron gases, such a those based on GaAs. However, in a recent paper published in Metrologia, polymer encapsulated epitaxial graphene (epigraphene) is shown to be a viable candidate for a quantum Hall resistance standard. The devices, now used by the National Physical Laboratory (NPL), had been thermally cycled several times over three years with no significant drift in performance. The performance in question is also significantly higher than GaAs, enabling operation at higher temperatures and lower magnetic fields.
Sergey Kubatkin from Chalmers University of Technology (Chalmers) explains more: “With the new definitions of certain units within the International System of Units (SI) coming into effect since May 20th 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.”
The long-term collaboration between the Graphensic, Chalmers, and NPL has now resulted in commercially viable quantum Hall effect devices that are offered by Graphensic for use as primary standards or research purposes.