Simon Thomas, Ivor Guiney, Colin Humphreys*

Paragraf Ltd, Somersham, Cambridge,UK
*School of Engineering and Materials Science, Queen Mary University of London, UK

In 2015, Bosch issued a press release claiming that their Hall effect magnetic sensor made from an exfoliated flake of graphene was the most sensitive in the world, but they added that graphene-based sensor applications will require 5-10 years before they can compete with established technologies because of the currect lack of large-scale wafer-based and transfer-free systhesis techniques.

Large-area (up to 4-inch diameter so far) sheets of graphene produced by chemical vapour deposition (CVD) are available, but the CVD process uses a metal substrate, usually copper, as a catalyst to decompose the growth gases used. This results in copper atoms being incorporated in the graphene. The graphene then needs to be removed from the copper substrate using, for example, iron chloride, resulting in further contamination with iron as well as copper. Such large-area CVD graphene has been attempted to be used in electronic device manufacturing, however the contamination has proven to be a completely limiting factor.

We have produced large-area graphene directly on a substrate and it is therrefore free of metallic contamination. In response to the press release of Bosch, quoted above, we have produced a graphene Hall sensor for measuring magnetic fields. It is the most sensitive Hall sensor in the world and is manufacturable. It promises to revolutionise sensors, photonics and electronics.