German researchers have created a magnetic sensor from graphene that is 100 times more sensitive than a silicon-based alternative.
The device, presented at the Graphene Flagship Conference in Manchester this week, was developed by Bosh engineer Robert Roelver in cooperation with scientists from the Max-Planck Institute for Solid State Research.
Bosh, the leading manufacturer of sensors for the automotive industry, has been investigating graphene for its potential to improve existing applications and to enable new ones.
The firm’s engineers explored techniques that might be suitable for the mass production of graphene-based devices, including thermal decomposition and chemical vapour deposition.
The researchers experimented with various substrates for their magnetic sensor and eventually settled on hexagonal boron nitride due to its favourable cost and good performance.
According to Roelver, even the worst of the graphene-based sensors roughly matched a silicon reference, with the best one being up to 100 times more sensitive than the silicon-based alternative.
Bosch's magnetic sensors are based on the Hall effect, in which a magnetic field induces a Lorentz force on moving electric-charge carriers, leading to deflection and a measurable Hall voltage.
The sensitivity of such a sensor is defined by the number of charge carriers, while its performance is limited by the overall power consumption. Graphene excels in this field because of its high carrier mobility.
As explained by Roelver, a silicon sensor has a sensitivity of 70 volts per amp-tesla, whereas the boron nitride and graphene device offers 7,000.
“We are pleased to see that Graphene Week has been chosen as the forum to disclose such an important technological milestone,” said Andrea Ferrari, chairman of the Executive Board of the Graphene Flagship. “Bosch's call for large-area integration of graphene into industrial processes fully matches and validates the flagship's planned investments in this critical area for the mass production of devices.”
Although Roelver warned that graphene-based sensor applications will require five to ten years before they can compete with established technologies, he expressed confidence the wonder material would eventually lead to major developments in many areas.
Bosh wants to use graphene-based sensors in future to measure pressure, magnetism, humidity and gas and sound pressure. Such sensors are used frequently in automobiles, as well as consumer electronic devices including smartphones and tablets.
Currently, the major limitation for the development of large-scale graphene sensor production is the lack of large-scale wafer-based and transfer-free synthesis techniques.