Programmable graphene resistance standards

Realisation of the resistance unit ohm and the voltage unit volt is fundamental in electrical metrology. These realisations are the basis for all calibration within the electrical quantities. It is therefore important for the National Laboratory for electrical quantities to develop these methods as they affect most of our electrified and connected society.

Quantum Hall arrays and graphene

Resistance is realised through the quantum hall effect. Graphene is well established as the best material for this realisation. Traditionally, the realisation takes place at a level close to 12.9 kΩ. In several previous projects, RISE has taken a world-leading role in developing matrices of connected quantum hall elements, so-called quantum hall arrays, to realize resistance at an arbitrary level. These standards lead to better measurement uncertainty as the number of calibration steps becomes fewer. The development has attracted the attention of both other national metrology institutes and industrial actors.

Currently, each desired resistance level requires a separate quantum hall array, which often has to be custom-made on a separate chip. It takes time and resources to manufacture and switch these quantum hall arrays when calibrating at different resistance levels.

A programmable quantum hall array

A programmable quantum hall array is the ultimate version of a resistance standard and would radically streamline resistance calibration. With a programmable resistance standard, the operator can easily set the desired resistance level at each calibration, saving a lot of time and resources.

A parallel can be drawn to the development in realising the unit for voltage, volt, which is increasingly dominated by programmable Josephson standards.

The concept of programmable quantum hall arrays has been tested on a smaller scale by, for example, the American National Institute of Standards and Technology and the German Physikalisch-Technische Bundesanstalt, but the measurement uncertainty has not reached the required low level.

First steps

By using the methods we previously developed, the project will take the first steps towards a programmable graphene resistance standard that meets the high demands, by designing, developing and testing small-scale programmable quantum hall arrays.