Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > The dispute about the origins of terahertz photoresponse in graphene results in a draw

Photoresponse in graphene.
CREDIT
Lion_on_helium, MIPT press office
Photoresponse in graphene. CREDIT Lion_on_helium, MIPT press office

Abstract:
Physicists at MIPT and their British and Russian colleagues revealed the mechanisms leading to photocurrent in graphene under terahertz radiation. The paper published in Applied Physics Letters not only puts a period to a long-lasting debate about the origins of direct current in graphene illuminated by high-frequency radiation but also sets the stage for the development of high-sensitivity terahertz detectors. Such detectors are highly demanded in medical diagnostics, wireless communications and security systems.

The dispute about the origins of terahertz photoresponse in graphene results in a draw

Moscow, Russia | Posted on April 26th, 2018

In 2005 MIPT alumni Andre Geim and Konstantin Novoselov experimentally studied the behavior of electrons in graphene, a flat honeycomb lattice of carbon atoms. They found that electrons in graphene respond to electromagnetic radiation with an energy of quantum, whereas the common semiconductors have an energy threshold below which the material does not respond to light at all. However, the direction of electron motion in graphene exposed to radiation has long remained a point of controversy, as there is a plenty of factors pulling it in different directions. The controversy was especially stark in the case of the photocurrent caused by terahertz radiation.

What sets terahertz radiation apart is its unique set of properties. As an example, it easily passes through many dielectrics without ionizing them: this is of particular value to medical diagnostic or security systems. A terahertz camera can "see" the weapons concealed under a person's clothes, and a medical scanner can detect skin diseases at early stages by the spectral lines ("fingerprints") of characteristic biomolecules in the terahertz range. Finally, raising the carrier frequency of Wi-Fi devices from several to hundreds of gigahertz (into the sub-terahertz range) will proportionally increase the bandwidth. But all these applications need a sensitive and low-noise terahertz detector which is simple in fabrication.

A terahertz detector designed by researchers at MIPT, MSPU and the University of Manchester (the place where graphene was first discovered) is a graphene sheet (colored green in figures 1 and 2) sandwiched between dielectric layers of boron nitride and electrically coupled to a terahertz antenna--a metal spiral about a millimeter in size. As radiation impinges on the antenna, it rocks electrons on one side of the graphene sheet, while the resulting direct current is measured on the other side. It is the "packing" of graphene into boron nitride that enables record-high electric characteristics, giving the detector a sensitivity that is a cut above the earlier designs. However, the main result of the research is not a better-performing instrument; it is the insight into the physical phenomena responsible for the photocurrent.

There are three main effects leading to the electric current flowing in graphene exposed to terahertz radiation. The first one, the photothermoelectric effect, is due to the temperature difference between the antenna terminal and the sensing terminal. This sends electrons from the hot terminal to the cold one, like air rising up from a warm radiator up to cold ceiling. The second effect is the rectification of current at the terminals: it turns out that the edges of graphene let through only the high-frequency signal of a certain polarity. The third and most interesting effect is called plasma wave rectification. We can think of the antenna terminal as stirring up "waves in the electronic sea" of the graphene strip, while the sensing terminal registers the average current associated with these waves.

"Earlier attempts to explain the photocurrent in such detectors used only one of these mechanisms and excluded all the others," says Dmitry Svintsov, head of the Laboratory of 2d Materials' Optoelectronics at MIPT. "In reality, all three of them are at play, and our study found which effect dominates at which conditions. Thermoelectric effects dominate at low temperatures, while plasmonic rectification prevails at high temperatures and in longer-channel instruments. And the main thing is that we figured out how to make a detector in which the different photoresponse mechanisms will not cancel each other, but rather reinforce each other"

These experiments will help choose the best design for terahertz detectors and bring us closer to remote detection of dangerous substances, safe medical diagnostics, and high-speed wireless communications.

###

The work was supported by the Russian Science Foundation, the Ministry of Education and Science of the Russian Federation, the Leverhulme Trust (Great Britain) and the Russian Foundation for Basic Research.

####

For more information, please click here

Contacts:
Ilyana Zolotareva

977-771-4699

Copyright © Moscow Institute of Physics and Technology

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related Links

RELATED JOURNAL ARTICLE:

Related News Press

News and information

Nano-kirigami: 'Paper-cut' provides model for 3D intelligent nanofabrication July 13th, 2018

UMBC researchers develop nanoparticles to reduce internal bleeding caused by blast trauma July 13th, 2018

Leti and Oscaro Partner on Letiís New Low-Power, Low-Cost Transceiver to Track Parcels July 12th, 2018

Oxford Instrumentsí 22 Tesla superconducting magnet system commissioned at the UAM, making it the most intense magnetic field available outside a large international facility July 12th, 2018

Nanometrics to Announce Second Quarter Financial Results on July 31, 2018 July 12th, 2018

Wireless/telecommunications/RF/Antennas/Microwaves

Leti and Oscaro Partner on Letiís New Low-Power, Low-Cost Transceiver to Track Parcels July 12th, 2018

GLOBALFOUNDRIES Surpasses $2 Billion in Design Win Revenue on 22FDXģ Technology : With 50 client designs and growing, 22FDX proves its value as a cost-effective solution for power-sensitive applications July 9th, 2018

Powering the 21st Century with Integrated Photonics: UCSB-Led Team Selected for Demonstration of a Novel Waveguide Platform Which is Transparent Throughout the MWIR and LWIR Spectral Bands June 19th, 2018

Squeezing light at the nanoscale: Ultra-confined light could detect harmful molecules June 17th, 2018

Graphene/ Graphite

NIST Researchers Simulate Simple Logic for Nanofluidic Computing June 30th, 2018

Making quantum puddles: Physicists discover how to create the thinnest liquid films ever June 13th, 2018

Law enforcement/Anti-Counterfeiting/Security/Loss prevention

Northwestern researchers achieve unprecedented control of polymer grids: Materials could find applications in water purification, solar energy storage, body armor June 22nd, 2018

Possible Futures

Nano-kirigami: 'Paper-cut' provides model for 3D intelligent nanofabrication July 13th, 2018

UMBC researchers develop nanoparticles to reduce internal bleeding caused by blast trauma July 13th, 2018

Barium ruthenate: A high-yield, easy-to-handle perovskite catalyst for the oxidation of sulfides July 13th, 2018

Leti and Oscaro Partner on Letiís New Low-Power, Low-Cost Transceiver to Track Parcels July 12th, 2018

Discoveries

Nano-kirigami: 'Paper-cut' provides model for 3D intelligent nanofabrication July 13th, 2018

UMBC researchers develop nanoparticles to reduce internal bleeding caused by blast trauma July 13th, 2018

Barium ruthenate: A high-yield, easy-to-handle perovskite catalyst for the oxidation of sulfides July 13th, 2018

Researchers identify cost-cutting option in treating nail fungus with nanotechnology: GW researcher Adam Friedman, M.D., studied the potential use of nitric oxide-releasing nanoparticles to improve onychomycosis treatment July 11th, 2018

Announcements

Nano-kirigami: 'Paper-cut' provides model for 3D intelligent nanofabrication July 13th, 2018

UMBC researchers develop nanoparticles to reduce internal bleeding caused by blast trauma July 13th, 2018

Barium ruthenate: A high-yield, easy-to-handle perovskite catalyst for the oxidation of sulfides July 13th, 2018

Leti and Oscaro Partner on Letiís New Low-Power, Low-Cost Transceiver to Track Parcels July 12th, 2018

Interviews/Book Reviews/Essays/Reports/Podcasts/Journals/White papers

Nano-kirigami: 'Paper-cut' provides model for 3D intelligent nanofabrication July 13th, 2018

UMBC researchers develop nanoparticles to reduce internal bleeding caused by blast trauma July 13th, 2018

Barium ruthenate: A high-yield, easy-to-handle perovskite catalyst for the oxidation of sulfides July 13th, 2018

Researchers identify cost-cutting option in treating nail fungus with nanotechnology: GW researcher Adam Friedman, M.D., studied the potential use of nitric oxide-releasing nanoparticles to improve onychomycosis treatment July 11th, 2018

Tools

Oxford Instrumentsí 22 Tesla superconducting magnet system commissioned at the UAM, making it the most intense magnetic field available outside a large international facility July 12th, 2018

Nanometrics to Announce Second Quarter Financial Results on July 31, 2018 July 12th, 2018

Nanometrics to Participate in the 10th Annual CEO Investor Summit 2018: Accredited investor and publishing research analyst event held concurrently with SEMICON West and Intersolar 2018 in San Francisco June 28th, 2018

The Institute of Applied Physics at the University of Tsukuba near Tokyo in Japan uses Deben's ARM2 detector to better understand catalytic reaction mechanisms June 27th, 2018

Homeland Security

Northwestern researchers achieve unprecedented control of polymer grids: Materials could find applications in water purification, solar energy storage, body armor June 22nd, 2018

Powering the 21st Century with Integrated Photonics: UCSB-Led Team Selected for Demonstration of a Novel Waveguide Platform Which is Transparent Throughout the MWIR and LWIR Spectral Bands June 19th, 2018

Squeezing light at the nanoscale: Ultra-confined light could detect harmful molecules June 17th, 2018

Nuclear radiation detecting device could lead to new homeland security tool: New device can detect gamma rays and identify radioactive isotopes April 25th, 2018

Battery Technology/Capacitors/Generators/Piezoelectrics/Thermoelectrics/Energy storage

Carbon is the new black: Researchers use carbon nanotubes to develop clothing that can double as batteries July 10th, 2018

NIST Researchers Simulate Simple Logic for Nanofluidic Computing June 30th, 2018

BNAs improve performance of Li-ion batteries June 27th, 2018

Northwestern researchers achieve unprecedented control of polymer grids: Materials could find applications in water purification, solar energy storage, body armor June 22nd, 2018

NanoNews-Digest
The latest news from around the world, FREE



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project