Graphene Devices for Tabletop and High-Current Quantized Hall Resistance Standards

Abstract

We report the performance of a quantum Hall resistance standard based on epitaxial graphene maintained in a 5-T tabletop cryocooler system. This quantum resistance standard requires no liquid helium and can operate continuously, allowing year-round accessibility to quantized Hall resistance measurements. The ν = 2 plateau, with a value of RK/2, also seen as RH, is used to scale to 1 kΩ using a binary cryogenic current comparator (BCCC) bridge and a direct current comparator (DCC) bridge. The uncertainties achieved with the BCCC are such as those obtained in the state-of-the-art measurements using GaAs-based devices. BCCC scaling methods can achieve large resistance ratios of 100 or more, and while room temperature DCC bridges have smaller ratios and lower current sensitivity, they can still provide alternate resistance scaling paths without the need for cryogens and superconducting electronics. Estimates of the relative uncertainties of the possible scaling methods are provided in this report, along with a discussion of the advantages of several scaling paths. The tabletop system limits are addressed as are potential solutions for using graphene standards at higher currents.

Atypical quantized resistances in millimeter-scale epitaxial graphene p-n junctions

“…[1][2][3][4] Epitaxial graphene (EG) on silicon carbide (SiC), which can be grown on the centimeter scale and is one of the many methods of synthesizing graphene, exhibits properties that render it suitable for large-scale or high-current applications such as the continued development of quantized Hall resistance (QHR) standards. [5][6][7][8][9][10][11][12][13][14][15] Though modernday standards using millimeter-scale EG have been shown to have long-term electrical stability in ambient conditions, 16 these devices are, in most cases, only able to output a single value of quantized resistance (ν = 2 plateau) to a degree of accuracy which warrants possible use in metrology. The corresponding value is: One milestone for graphene QHR standards would be the eventual accessibility of different resistance values that are well-quantized.…”

The quantum Hall effect in the era of the new SI

“…The labelled GaAs devices can be traced to the following references: A - [39], B - [91], C - [18], D - [27]. The labelled EG devices can be traced to the following references: A - [91], B - [75], C - [77], D - [92], E to G - [73], H - [92]. (a) The optimization process for EG-based devices made at NIST took several years to accomplish, with the first crucial milestone being the successful growth of uniform single layer EG as opposed to overgrown or undergrown (i.e.…”

A quantum ampere

“…2) at lower magnetic fields (5 T or lower), higher measurement currents (up to hundreds of µA) and higher temperatures (5 K) was demonstrated [35]. These conditions allow to implement tabletop quantum Hall resistance standards using small, inexpensive dry cryocoolers [36,37], suitable to be continuously operated in a calibration laboratory. Research is now focusing on achieving better reproducibility of fabrication and long-term stability of the devices.…”