Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The photoexcited graphene puzzle solved

14.05.2018

A boost for graphene-based light detectors

Light detection and control lies at the heart of many modern device applications, such as the camera you have in your phone. Using graphene as a light-sensitive material for light detectors can offer significant improvements with respect to materials being used nowadays.


Schematic representation of the ultrafast optical pump - terahertz probe experiment, where the optical pump induces electron heating and the terahertz pulse is sensitive to the conductivity of graphene directly after this heating process, which occurs on a timescale faster than a millionth of a millionth of a second

Credit: Illustration: Fabien Vialla/ICFO

For example, graphene can detect light of almost any colour, and it gives an extremely fast electronic response within one millionth of a millionth of a second. Thus, in order to properly design graphene-based light detectors it is crucial to understand the processes that take place inside the graphene after it absorbs light.

A team of European scientists including ICFO from Barcelona (Spain), IIT from Genova (Italy), the University of Exeter from Exeter (UK) and Johannes Gutenberg University from Mainz (Germany), have now succeeded in understanding these processes.

Published recently in Science Advances, their work gives a thorough explanation of why, in some cases, the graphene conductivity increases after light absorption and in other cases, it decreases. The researchers show that this behaviour correlates with the way in which energy from absorbed light flows to the graphene electrons: After light is absorbed by the graphene, the processes through which graphene electrons heat up happen extremely fast and with a very high efficiency.

For highly doped graphene (where many free electrons are present), ultrafast electron heating leads to carriers with elevated energy - hot carriers - which, in turn, leads to a decrease in conductivity. Interestingly enough, for weakly doped graphene (where not so many free electrons are present), electron heating leads to the creation of additional free electrons, and therefore an increase in conductivity. These additional carriers are the direct result of the gapless nature of graphene - in gapped materials, electron heating does not lead to additional free carriers.

This simple scenario of light-induced electron heating in graphene can explain many observed effects. Aside from describing the conductive properties of the material after light absorption, it can explain carrier multiplication, where - under specific conditions - one absorbed light particle (photon) can indirectly generate more than one additional free electron, and thus create an efficient photoresponse within a device.

The results of the paper, in particular, understanding electron heating processes accurately, will definitely mean a great boost in the design and development of graphene-based light detection technology.

###

This work was funded by the E.C. under Graphene Flagship, as well as a Mineco Young Investigator grant.

Media Contact

Alina Hirschmann
alina.hirschmann@icfo.eu
34-935-542-246

http://www.icfo.es

Alina Hirschmann | EurekAlert!

More articles from Materials Sciences:

nachricht Princeton-UPenn research team finds physics treasure hidden in a wallpaper pattern
20.07.2018 | Princeton University

nachricht Relax, just break it
20.07.2018 | DOE/Argonne National Laboratory

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Future electronic components to be printed like newspapers

A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.

The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

A smart safe rechargeable zinc ion battery based on sol-gel transition electrolytes

20.07.2018 | Power and Electrical Engineering

Reversing cause and effect is no trouble for quantum computers

20.07.2018 | Information Technology

Princeton-UPenn research team finds physics treasure hidden in a wallpaper pattern

20.07.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>