Researchers at Chalmers University of Technology in Sweden have developed a first-of-its-kind flexible detector for terahertz frequencies using graphene transistors on plastic substrates.
Terahertz radiation can be used in everything from airport security and medical imaging to wireless communication.
However, the difficulty of applying terahertz detectors to low-cost, flexible substrates has so far limited the technology to larger, more expensive applications such as security scanners.
The detector, which is presented in a paper in the journal Applied Physics Letters, could extend the use of terahertz technology to applications such as wearable electronics and low-cost wireless sensor networks.
Terahertz radiation refers to electromagnetic waves whose frequencies range from 100GHz to 10THz.
To develop the terahertz detector, the team at Chalmers used chemical vapour deposition to grow a single-layer graphene sheet, which they then transferred to a 10cm wide, 175µm thick plastic substrate.
They then used electron beam lithography to fabricate the electronic circuits needed to create the detector.
Graphene is a promising material for terahertz detectors, as it is flexible and mechanically stable, and is a good conductor of electricity, according to Professor Jan Stake, head of the Terahertz and Millimetre Wave Laboratory at Chalmers.
“Graphene has the advantage of both good electrical properties and good mechanical properties,” said Stake. “It could be used in sensors that are placed close to the body, or even for imaging applications.”.
At room temperature, the translucent, flexible device can detect signals in the range of 330 to 500GHz.
As well as medical and consumer applications, the detector could also be used as a sensor on vehicles, where it could provide visibility at night and through rain, snow and fog.
“This a proof of concept, showing one circuit that operates on very high frequencies on a plastic substrate … so the goal is to take it further into more advanced concepts,” said Stake.
Options include developing an array of terahertz detectors, and forming it into the shape required for imaging applications.
The research was funded by the EU Graphene Flagship, the Swedish Foundation for Strategic Research (SSF), and the Knut and Alice Wallenberg Foundation (KAW). The detector was recently presented at the EU Tallinn Digital Summit.
