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Singapore develops super sensitive hybrid sensor

Posted: 03 Nov 2015 ?? ?Print Version ?Bookmark and Share

Keywords:hybrid sensor? graphene? magnetoresistance?

National University of Singapore (NUS) researchers have created a hybrid magnetic sensor that is more sensitive than existing sensors available in the market. This innovation paves the way for the development of smaller and cheaper sensors for such applications as consumer electronics, biotechnology, automotive, and information and communication technology.

The invention, led by Associate Professor Yang Hyunsoo of the Department of Electrical and Computer Engineering at NUS' Faculty of Engineering, was published in the journal Nature Communications.

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 disc drives and other devices, transforming how data is stored and read.

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 developed by the team led by Yang, who is also with the NUS Nanoscience and Nanotechnology Institute (NUSNNI) and the Centre for Advanced 2D Materials (CA2DM) at NUS Faculty of Science, may finally meet these requirements. Other members of the interdisciplinary research team include Dr Kalon Gopinadhan of NUSNNI and CA2DM; Professor Thirumalai Venkatesan, Director of NUSNNI; Professor Andre K. Geim of the University of Manchester; and Professor Antonio H. Castro Neto of the NUS Department of Physics and Director of CA2DM.

More than 200 times more sensitive

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.

"We started by trying to understand how graphene responds under the magnetic field," Kalon said. "We found that a bilayer structure of graphene and boron nitride displays an extremely large response with magnetic fields. This 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 127C (the maximum temperature which most electronics products are operated at), 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 multi-layers can be partially adjusted by tuning the voltage across the sensor, enabling the sensor's characteristics to be optimised. This control gives the material an advantage over commercially available sensors. In addition, the sensor showed very little temperature dependence over room temperature to 127C range, making it an ideal sensor suitable for environments of higher temperature.

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