A team of Cornell University researchers have devised a tiny magnetic field sensor using a graphene and hexagonal boron (hBN) “sandwich.” The sensor works at any temperature, and is capable of detecting very small changes in magnetic fields that would otherwise be impossible to see within a larger magnetic background, according to Graphene-info.
The team’s approach looks to improve on the existing sensor technology, Hall-effect sensors, which are less capable of detecting the tiny field changes than their “sandwich.” Hall-effect sensors are used in everything from mobile phones to anti-lock brakes, and are typically made from semiconductors like silicon.
hBN has a similar crystalline structure to graphene, but its electricity insulating properties allow the graphene sheet to lie flat. The graphene layers in the “sandwich” then govern how many electrons can conduct electricity in the graphene.
The team’s sensors are so effective they can spot magnetic field fluctuations against a field a million times their size. Their goal is to incorporate the sensor into a scanning probe microscope to look at quantum materials and natural phenomena like magnetic fields and current flows.
“This work puts ultraclean graphene really on the map for being a superior material to build Hall probes out of. It wouldn’t be really practical for some applications because it’s hard to make these devices. But there are different pathways for materials growth and automated assembly of the sandwich that people are exploring. Once you have the graphene sandwich, you can put it anywhere and integrate it with existing technology,” said team lead Katja Nowack.