Graphene and hexagonal boron nitride have been used to create new, ultra-sensitive Hall effect sensors.
Magnetic field sensors are in high demand in various industries, such as the consumer electronics industry and vehicle production. These sensors offer precise measurements of position, proximity and motion. Of the most popular types of sensor available, Hall effect sensors are the most durable and cost effective.
The most commonly used Hall effect devices are currently fabricated with silicon. The important figures of merit of Hall sensors are voltage and current-related sensitivities. These sensitivities depend on the electronic properties of the device materials, such as charge carrier mobility and density. However, more advanced applications require higher sensitivity Hall sensors. The other well-known materials are based on high purity III-V semiconductors like GaAs- or InAs-based heterostructures. While a lot of effort has been made to develop sensors using these materials, sensitivity values are restricted.
Now researchers have fabricated highly-sensitive Hall effect sensors using single layer graphene. Graphene, a two dimensional atomic form of carbon, is a potential candidate for highly-sensitive Hall sensors because of its very high carrier mobility at room temperature and very low carrier densities. These properties make graphene a material that can outperform all currently existing Hall sensor technologies.
Researchers have protected the graphene from ambient contaminations by encapsulating it with hexagonal boron nitride layers, another highly promising 2D insulating material. The fabricated devices show a voltage and current normalized sensitivity of up to 3 V/VT and 5700 V/AT, respectively. These values are more than one order of magnitude above the values achieved in silicon-based sensors and a factor of two above the values achieved with the best sensors using III-V semiconductors in ambient conditions.
This new sensitivity level will allow for devices with higher precision and lower energy consumption. This work will enable the use of graphene in more commercial applications, as Hall sensors are an integral part of many household appliances.
The research was conducted by RWTH University and AMO GmbH Aachen. The results were published in the journal Applied Physics Letters.
