Cleaner graphene for improved electronics

Researchers at the National Graphene Institute, UK, claim to have produced the cleanest graphene yet.

This allows quantum phenomena to appear in magnetic fields as weak as the Earth’s own.

The work, reported in Nature by a team led by Professor Andre Geim, was achieved by placing a sheet of graphene three atoms below cleaner bulk graphite. This ‘proximity mirror’ cancels out unwanted electric fields, reducing disorder in graphene by a factor of 100.

First author Dr Daniil Domaretskiy explains. ‘We’ve removed almost all the dirt that disrupts smooth flow of electric current. You can suddenly see effects that were hidden, like wiping clean a fogged-up window.’ In quantum materials, disorder hides delicate effects and can prevent new physics from emerging.

The low disorder level in the cleaner graphene mean that electrons travel faster and further than before.

Key benchmarks of material quality, such as Shubnikov–de Haas oscillations, are now visible at fields below 10 Gauss. The celebrated quantum Hall effect appears below 50 Gauss.

The concept is straightforward. The nearby graphite acts like an electrical mirror, cancelling random electric fields in the graphene layer. The challenge was engineering the mirror close enough, three atoms apart, without damaging the graphene.

The team expects that the proximity-mirror technique will become standard for probing quantum phenomena in 2D materials, enabling new discoveries in superconductivity, magnetism and exotic quantum phases, which would all benefit from ultra-clean electronic conditions.

The work involved collaborators from Lancaster University, the National University of Singapore, and the National Institute for Materials Science in Japan.