New research at the University of Maryland could lead to a generation of light detectors that can see below the surface of bodies, walls, and other objects.
Using the special properties of graphene, a two-dimensional form of carbon that is only one atom thick, a prototype detector is able to see an extraordinarily broad band of wavelengths. Included in this range is a band of light wavelengths that have exciting potential applications but are notoriously difficult to detect: terahertz waves, which are invisible to the human eye.
A research paper about the new detector was published online Sept. 7, 2014 in the journal Nature Nanotechnology. Lead author Xinghan Cai, a UMD physics graduate student, said a detector like the researchers’ prototype “could find applications in emerging terahertz fields such as mobile communications, medical imaging, chemical sensing, night vision and security.”
The light we see illuminating everyday objects is actually only a very narrow band of wavelengths and frequencies. Terahertz light waves’ long wavelengths and low frequencies fall between microwaves and infrared waves. The light in these terahertz wavelengths can pass through materials that we normally think of as opaque, such as skin, plastics, clothing and cardboard. It can also be used to identify chemical signatures that are emitted only in the terahertz range.
Few technological applications for terahertz detection are currently realized, however, in part because it is difficult to detect light waves in this range. In order to maintain sensitivity, most detectors need to be kept extremely cold, around 4 Kelvin, or -452 degrees Fahrenheit. Existing detectors that work at room temperature are bulky, slow and prohibitively expensive.
The new room temperature detector, developed by the UMD team and colleagues at the U.S. Naval Research Lab and Monash University, Australia, gets around these problems by using graphene, a single layer of interconnected carbon atoms. By utilizing the special properties of graphene, the research team has been able to increase the speed and maintain the sensitivity of room temperature wave detection in the terahertz range.
Using a new operating principle called the “hot-electron photothermoelectric effect,” the research team created a device that is “as sensitive as any existing room temperature detector in the terahertz range and more than a million times faster,” says Michael Fuhrer, professor of physics at UMD and Monash University.
Graphene, a sheet of pure carbon only one atom thick, is uniquely suited to use in a terahertz detector because when light is absorbed by the electrons suspended in the honeycomb lattice of the graphene, they do not lose their heat to the lattice but instead retain that energy.
The concept behind the detector is simple, says UMD Physics Professor Dennis Drew. “Light is absorbed by the electrons in graphene, which heat up but don’t lose their energy easily. So they remain hot while the carbon atomic lattice remains cold.” These heated electrons escape the graphene through electrical leads, much like steam escaping a tea kettle. The prototype uses two electrical leads made of different metals, which conduct electrons at different rates. Because of this conductivity difference, more electrons will escape through one than the other, producing an electrical signal.
This electrical signal detects the presence of terahertz waves beneath the surface of materials that appear opaque to the human eye--or even X-rays. You cannot see through your skin, for example, and an X-ray goes right through the skin to the bone, missing the layers just beneath the skin’s surface entirely. Terahertz waves see the in-between. The speed and sensitivity of the room temperature detector presented in this research opens the door to future discoveries in this in-between zone.
This research was supported by the U.S. Office of Naval Research (Award Nos. N00014911064, N000141310712, N00014441310865), the National Science Foundation (Award No. ECCS 1309750) and the Intelligence Advanced Research Projects Activity. The content of this article does not necessarily reflect the views of these organizations.
The research paper, “Sensitive Room-Temperature Terahertz Detection via Photothermoelectric Effect in Graphene,” Xinghan Cai, Andrei B. Sushkov, Ryan J. Suess, Mohammad M. Jadidi, Gregory S. Jenkins, Luke O. Nyakiti, Rachael L. Myers-Ward, Jun Yan, Shanshan Li, D. Kurt Gaskill, Thomas E. Murphy, H. Dennis Drew, and Michael S. Fuhrer, was published Sept. 7, 2014 in Nature Nanotechnology.
Media Relations Contact: Heather Dewar, 301-405-9267, email@example.com
About the College of Computer, Mathematical, and Natural Sciences
The College of Computer, Mathematical, and Natural Sciences at the University of Maryland educates more than 7,000 future scientific leaders in its undergraduate and graduate programs each year. The college’s 10 departments and more than a dozen interdisciplinary research centers foster scientific discovery with annual sponsored research funding exceeding $150 million.
Kathryn Tracey | Eurek Alert!
Astronomers find unexpected, dust-obscured star formation in distant galaxy
24.03.2017 | University of Massachusetts at Amherst
Gravitational wave kicks monster black hole out of galactic core
24.03.2017 | NASA/Goddard Space Flight Center
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
24.03.2017 | Materials Sciences
24.03.2017 | Physics and Astronomy
24.03.2017 | Physics and Astronomy