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NUS scientists develop super sensitive magnetic sensor

31 October 2015

Researchers from the National University of Singapore have developed a new hybrid magnetic sensor that is more sensitive than most commercially available sensors.

Members of the NUS research team pose with one of their new sensors (photo: National University of Singapore)

This technological breakthrough hails opportunities for the development of smaller and cheaper sensors for various fields, such as consumer electronics, information and communication technology, biotechnology and automotive. The work was led by Associate Professor Yang Hyunsoo of the Department of Electrical and Computer Engineering at the National University of Singapore (NUS) Faculty of Engineering, 

When an external magnetic field is applied to certain materials, a change in electrical resistance - also known as magnetoresistance - occurs as the electrons are deflected. The discovery of magnetoresistance paved the way for magnetic field sensors used in hard disk drives and other devices.

In the search for an ideal magnetoresistance sensor, researchers have prized the properties of high sensitivity to low and high magnetic fields, tunability, and very small resistance variations due to temperature. The new hybrid sensor may finally meet these requirements.

The new sensor, made of graphene and boron nitride, comprises a few layers of carrier-moving channels, each of which can be controlled by the magnetic field. The researchers characterised the new sensor by testing it at various temperatures, angles of magnetic field, and with a different pairing material.

The researchers found that a bilayer structure of graphene and boron nitride displays an extremely large response with magnetic fields, and the combination can be utilised for magnetic field sensing applications.

Compared to other existing sensors, which are commonly made of silicon and indium antimonide, the group’s hybrid sensor displayed much higher sensitivity to magnetic fields. In particular, when measured at 127°C (the maximum temperature at which most electronics products are operated), the researchers observed a gain in sensitivity of more than eight-fold over previously reported laboratory results and more than 200 times that of most commercially available sensors.

Another breakthrough in this research was the discovery that mobility of the graphene multilayers can be partially adjusted by tuning the voltage across the sensor, enabling the sensor’s characteristics to be optimised. In addition, the sensor showed very little temperature dependence over room temperature to 127°C range, making it an ideal sensor suitable for environments of higher temperature.

Graphene-based magnetoresistance sensors hold immense promise over existing sensors due to their stable performance over temperature variation, eliminating the necessity for expensive wafers or temperature correction circuitry. Production cost for graphene is also much lower than silicon and indium antimonide.

The research team has filed a patent for the invention. Following this proof-of-concept study, the researchers plan to scale up their studies and manufacture industry-size wafers for industrial use.

An article describing the work is published in the journal, Nature Communications.

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