Innovative technology could lead to better biochemical detectors

Researchers create more sensitive photodetector using thin graphene layers

By Doug Page

Better biochemical weapons detection and body scanners might result from a faster, more sensitive photodetector being developed at the University of Maryland.

Researchers at the UM's Center for Nanophysics and Advanced Materials have come up with a hot electron bolometer technology that can be used in everything from airport body scanners and standoff detection of chemical and biochemical weapons to laboratory chemical analysis and improved telescopes.

The UM bolometer uses two atom-thin sheets of graphene, whose unique properties make it sensitive to a broad range of light energies, from terahertz frequencies or submillimeter waves through infrared to visible light.

"The terahertz frequency range is an area of the electronic spectrum which is particularly difficult to detect, but is important for security applications, such as standoff detection of explosives or chemical weapons materials, and scanning of opaque objects such as structures or clothed people," said UM physics professor Michael Fuhrer.

Fuhrer said the graphene hot electron bolometer is an extremely sensitive terahertz detector, with sensitivity superior to the best existing superconducting transition edge detectors, plus it's much faster, which may allow for new modulated detection schemes.

Fuhrer added that graphene is easily fabricated over large areas, so detector arrays with wavelength-specific antennas for spectrometry, or pixels for imaging, could be manufactured easily.

Fuhrer admitted that while the UM graphene detector can operate at somewhat higher temperatures (around 20 Kelvin, or about -420 F) than current superconducting detectors, which operate within a few degrees of 0 Kelvin, or about -460 F, it is still a low-temperature device and requires a cryogenic cooling system. This probably precludes widespread use in homeland security applications at this time.

"However," he said, "the exciting aspect is that the basic principle that makes the detector so sensitive, the small electron-photon scattering in graphene which holds heat in the electron system, can be exploited in other detection schemes at higher temperatures."

Fuhrer said the UM team is currently working on new graphene detector schemes designed to operate at room temperature and be significantly more sensitive than the state-of-the-art pyroelectric detectors, and that may eventually be used to make faster, more sensitive chemical sensors and terahertz scanners. 

About the author
Since leaving a withering aerospace engineering career in 1994, Doug Page has been writing about technology, medicine, and marriage peril from the Panic Room in Pine Mountain, Calif. He won a 2006 Tabby Award for a story titled "Life in a Disaster Morgue" that appeared in the January 2006 issue of Forensic Magazine. From 1998-2008 he was the Technology Correspondent for Fire Chief Magazine. Page is also a former contributing editor for Homeland Protection Professional and Science Spectra magazines.


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