Industrial feasibility test of a graphene-enabled turnkey quantum resistance system

Benchmark: The minimum requirement for primary resistance metrology is to measure the quantum Hall resistance to better than 1 part per billion (or 1 nanoOhm/Ohm). When using traditional GaAs/AlGaAs heterostructues or Si MOSFETs this requires a measurement current of at least 25 microamps through the device without breakdown of the quantum Hall effect. To achieve this the temperature must be below 1 kelvin and the magnetic field around 10 tesla or higher to achieve robust Landau quantisation.

Benefit of graphene: Graphene improves on this in several ways: firstly the Landau quantisation is intrinsically much stronger (factor of 5 at 10 T). Secondly, because of the specific phonon spectrum and electron-phonon coupling strength the relaxation of hot carriers in graphene is 10 times faster than in GaAs, resulting in a much larger breakdown current. The combination of these two unique graphene properties mean that a superior quantum Hall resistance can be constructed. However, so far these effects have been demonstrated in academic research and the advanced laboratory conditions at the National Physical Laboratory.

Targetted improvement: The challenge of this project to take these results forwards and make these measurements routine in a simple turn-key cryogen-free magneto-transport system. Specifically the project needs to address the noise levels produced in cryogen-free pulse-tube coolers, the control of the charge carrier density and homogeneity at very low carrier densities, and ability to perform ppb-level measurements outside metrology laboratory.

The business opportunity that this project will create is that of a significant market share for high-precision primary resistance metrology and graphene characterisation tools. A cryogen-free quantum Hall system based on graphene, GQHER, will reduce the traceability chain for resistance metrology and lead to higher measurement accuracies directly on the factory floor where precision equipment is manufactured. Higher accuracies in measurement technologies enable novel appilications. For example, more accurate atomic clocks have led directly to more accurate GPS and location services, enabling a host of high-tech applications. Similarly in electrical metrology, more accurate resistance measurements will lead to more accurate sensors and therefore better process control. For example, temperature control is often based on the measurement of very precise platinum resistors on the parts per million level which is right at the limit of what is possible today. This is about a factor of a 1000 worse than what you would potentially get from the QHE directly and results from the fact that the factory calibration is many steps removed from the primary realisation in the metrology laboratory. Shortening this calibration chain is the key to improving the traceability. The expensive infrastructure for traditional quantum Hall systems and the operational cost and complexity of liquid helium are the major barriers to wide-spread use of the quantum Hall effect. These obstacle will be, now, removed, opening ways for the transferable universal quantum resistance standard to reach manufacturing floors in electronics industry.