A collaboration between Bosch, the Germany-based engineering giant, and scientists at the Max-Planck Institute for Solid State Research yielded fascinating results, shown in a presentation during Graphene Week 2015. The researchers jointly created a graphene-based magnetic sensor 100 times more sensitive than an equivalent device based on silicon.
The research team used hexagonal boron nitride as substrate for the magnetic sensor, which is based on the Hall effect (a magnetic field that induces a Lorentz force on moving electric charge carriers, leading to deflection and a measurable Hall voltage). Graphene's high carrier mobility makes it useful in sensing applications, and the results achieved by the Bosch-led team confirm this. The presentation displaying the team's results showed that the worst case graphene scenarios roughly match a silicon equivalent. In the best case scenario, the result is a huge improvement over silicon, with much lower source current and power requirements for a given Hall sensitivity. In short, graphene provides for a high-performance magnetic sensor with low power and footprint requirements.
The remarkable result focused on a direct comparison between the sensitivity of a silicon-based Hall sensor with that of the Bosch-MPI graphene device. The silicon sensor has a sensitivity of 70 volts per amp-tesla, whereas with the boron nitride and graphene device the figure is 7,000. That is a significant two orders of magnitude improvement. Following this remarkable result, Bosch stated that it regards graphene as a strong material suitable for commercial application.
Bosch is a world-leading supplier of microelectromechanical sensors, with €1bn in sales. It has a long-standing involvement in sensor technology, notably in the automotive sector. It has been investigating the use of graphene in its various sensing devices with focus on commercial-scale production, mainly bottom-up techniques like thermal decomposition of silicon carbide, and chemical vapour deposition onto metal surfaces. The company maintains, though, that graphene-based sensor applications will require 5-10 years before they can compete with established technologies due to the current lack of large-scale wafer-based and transfer-free synthesis techniques.