Graphene-based quantum Hall effect metrology

In the past few decades, major improvements in electrical standards have come from quantum solid-state physics. The discovery of the Josephson effect and the integer quantum Hall effect (QHE) led to the realization of reproducible and universal voltage and resistance standards directly linked to Planck's constant and the electron charge. In efforts to further improve the dissemination of quantum standards, graphene could be crucial for the development of a more convenient resistance standard that is able to benefit from recent helium-free cryogenic techniques. This fascinating material could also contribute to a revolutionary revision of the Systeme International of units by enabling convincing universality tests of the QHE. This article reports on metrological investigations of the QHE in graphene, with accuracy down to 10(-10), demonstrating that a quantum resistance standard more robust than existing GaAs-based ones can be developed. The various results highlight the impacts of graphene quality and graphene-substrate interactions on quantization accuracy and the advantage for metrology of fabrication techniques that are scalable over large sizes such as epitaxial growth or chemical vapor deposition, although no single technique is yet clearly superior for achieving the final goal of an improved quantum standard for resistance.