Epitaxial graphene for quantum resistance metrology

Abstract

Graphene-based quantised Hall resistance standards promise high precision for the unit ohm under less exclusive measurement conditions, enabling the use of compact measurement systems. To meet the requirements of metrological applications, national metrology institutes developed large-area monolayer graphene growth methods for uniform material properties and optimized device fabrication techniques. Precision measurements of the quantized Hall resistance showing the advantage of graphene over GaAs-based resistance standards demonstrate the remarkable achievements realized by the research community. This work provides an overview over the state-of-the-art technologies in this field.

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.…”

Two-Terminal and Multi-Terminal Designs for Next-Generation Quantized Hall Resistance Standards: Contact Material and Geometry

“…The device fabrication process, as shown in Fig. 1(a), is based on the technique of protecting the EG from lithographic residues with a thin Pd/Au layer to allow for contaminant-free graphene/metal contacts [10], [11]. The covered EG is then structured into the Hall bar geometry using a thicker Au metal masking layer and Ar plasma etching.…”

The quantum Hall effect in the era of the new SI

“…Figure 2 highlights the present-day parameter space over which one can realize the extraordinary precision of the QHR value in a 2D material [73][74][75][76][77][78][79][80][81]. It has been established that graphene-based QHE devices can exhibit a distinct advantage over GaAs-based devices when attempting to use low magnetic fields, higher temperatures, and larger currents [10]. Improvement of devices to expand accessibility is expected to correlate with the reduction in cost and complexity of QHR resistance standards for metrology as well as the associated laboratory measurement apparatus.…”