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THz radiation leads to powerful nanoscale sensors

Posted: 01 Apr 2013 ?? ?Print Version ?Bookmark and Share

Keywords:biosensing? THz radiation? body scanner?

A team of researchers from the A*STAR Institute of Materials Research and Engineering (IMRE) has observed that microstructures made up by pairs of touching semiconductor disks yield enhanced terahertz radiation in a tiny V-shaped gap, just a fraction of a micrometre wide. According to the scientists, the effects seen in the microfabricated semiconductor structure could be used in applications such as biosensing and airport security scanners.

Hua Teng and his co-workers developed tiny semiconductor structures made of the chemical elements indium and antimony. From this material, they produced disks of 20?m in diameter, which they arranged such that pairs just touched. The gap between contiguous disks was merely tens to hundreds of nanometers wide. When the researchers exposed the structures to THz radiation, they found that the radiation intensity in the gap was enhanced by more than a hundred times.

Terahertz radiation

Source: Wiley-VCH Verlag. Terahertz radiation is greatly enhanced in the tiny V-shaped gap, just a fraction of a micrometer wide, between pairs of touching semiconductor disks.

Confining and enhancing THz radiation is significant for two reasons, according to Teng. First, electromagnetic waves in the THz range can be used in a range of applications, for example, to study the structure of large biomolecules. As this sort of radiation can penetrate textiles but is less energetic than X-raysor microwavesit is also well suited for use in body scanners at airports. The second reason as to why the new results are important is more fundamental. "We have produced this particular touching-disc structure to test, in the THz regime, intriguing theoretical predictions made for optical radiation," noted Teng. "Building a device such as ours for visible light is much more challenging, as it would involve even smaller structures."

The now-verified theoretical predictions came from collaborators at Imperial College London in the UK. "For the present work, IMRE is in charge of the materials growth and the structure fabrication, while Imperial College contributes structure design and characterisation," stated Teng. The A*STAR researchers are now focused on practical applications: they will further explore the unique properties of their semiconductor materials and try to develop devices for THz technology. The group has already succeeded in tuning the THz response of their structure, meaning that they can conveniently adjust the frequency response of their device for different applications.

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