The development of a graphene chip has enabled significantly shorter traceability chains and more accurate measurements, with a more accurate and compact piece of equipment.

“NPL, Chalmers University of Technology and Graphensic, have demonstrated the long-term stability of the epigraphene quantum Hall chip, which represents a key step towards enabling end-users to maintain their own resistance standards.
 
The SI unit of resistance is realised at NPL using a quantum Hall effect device. Recent research on graphene devices has enabled the quantum Hall effect to be realised at both lower magnetic fields and higher temperatures, whilst still retaining part per billion accuracies. The detailed findings are published in a recent edition of Metrologia.
 
NPL in collaboration with Oxford Instruments is developing a table-top primary standard of resistance incorporating both a graphene quantum Hall effect device and a cryogenic current comparator in the same cryostat, in order to provide a compact and easy-to-operate system for metrology laboratories.
 
The long-term collaboration between NPL, Chalmers University of Technology 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.
 
JT Jansen from 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.”

 
Read full article Graphene paves the way for novel product enabling industrial users

Source: Phys Org by National Physical Laboratory

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