Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Speed bumps less important than potholes for graphene

For electrical charges racing through an atom-thick sheet of graphene, occasional hills and valleys are no big deal, but the potholes—single-atom defects in the crystal—they’re killers.

That’s one of the conclusions reached by researchers from the National Institute of Standards and Technology (NIST) and the Georgia Institute of Technology who created detailed maps of electron interference patterns in graphene to understand how defects in the two-dimensional carbon crystal affect charge flow through the material. The results, appearing in the July 13 issue of Science*, have implications for the design of graphene-based nanoelectronics.

A single layer of carbon atoms tightly arranged in a honeycomb pattern, graphene was long thought to be an interesting theoretical concept that was impossible in practice—it would be too unstable, and crumple into some other configuration. The discovery, in 2004, that graphene actually could exist touched off a rush of experimentation to explore its properties. Graphene has been described as a carbon nanotube unrolled, and shares some of the unique properties of nanotubes. In particular, it’s a so-called ballistic conductor, meaning that electrons flow through it at high speed, like photons through a vacuum, with virtually no collisions with the atoms in the crystal. This makes it a potentially outstanding conductor for wires and other elements in nanoscale electronics.

Defects or irregularities in the graphene crystal, however, can cause the electrons to bounce back or scatter, the equivalent of electrical resistance, so one key issue is just what sort of defects cause scattering, and how much" To answer this, the NIST-Georgia Tech team grew layers of graphene on wafers of silicon carbide crystals and mapped the sheets with a custom-built scanning tunneling microscope (STM) in the NIST Center for Nanoscale Science and Technology that can measure both physical surface features and the interference patterns caused by electrons scattering in the crystal. (Graphene on silicon carbide is a leading candidate for graphene-based nanoelectronics.)

The results are counter-intuitive. Irregularities in the underlying silicon carbide cause bumps and dips in the graphene sheet that lies over it rather like a blanket on a lumpy bed, but these relatively large bumps have only a minor effect on the electron’s passage. In contrast, missing carbon atoms in the crystal lattice cause strong scattering, the interference patterns rippling around them like waves hitting the piles of a pier. From a detailed analysis of these interference patterns, the team verified that electrons in the graphene sheet behave like photons, even at the nanometer scale.

Michael Baum | EurekAlert!
Further information:

More articles from Physics and Astronomy:

nachricht 'Frequency combs' ID chemicals within the mid-infrared spectral region
16.03.2018 | American Institute of Physics

nachricht Fraunhofer HHI have developed a novel single-polarization Kramers-Kronig receiver scheme
16.03.2018 | Fraunhofer-Institut für Nachrichtentechnik, Heinrich-Hertz-Institut, HHI

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

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

Im Focus: Locomotion control with photopigments

Researchers from Göttingen University discover additional function of opsins

Animal photoreceptors capture light with photopigments. Researchers from the University of Göttingen have now discovered that these photopigments fulfill an...

Im Focus: Surveying the Arctic: Tracking down carbon particles

Researchers embark on aerial campaign over Northeast Greenland

On 15 March, the AWI research aeroplane Polar 5 will depart for Greenland. Concentrating on the furthest northeast region of the island, an international team...

Im Focus: Unique Insights into the Antarctic Ice Shelf System

Data collected on ocean-ice interactions in the little-researched regions of the far south

The world’s second-largest ice shelf was the destination for a Polarstern expedition that ended in Punta Arenas, Chile on 14th March 2018. Oceanographers from...

Im Focus: ILA 2018: Laser alternative to hexavalent chromium coating

At the 2018 ILA Berlin Air Show from April 25–29, the Fraunhofer Institute for Laser Technology ILT is showcasing extreme high-speed Laser Material Deposition (EHLA): A video documents how for metal components that are highly loaded, EHLA has already proved itself as an alternative to hard chrome plating, which is now allowed only under special conditions.

When the EU restricted the use of hexavalent chromium compounds to special applications requiring authorization, the move prompted a rethink in the surface...

Im Focus: Radar for navigation support from autonomous flying drones

At the ILA Berlin, hall 4, booth 202, Fraunhofer FHR will present two radar sensors for navigation support of drones. The sensors are valuable components in the implementation of autonomous flying drones: they function as obstacle detectors to prevent collisions. Radar sensors also operate reliably in restricted visibility, e.g. in foggy or dusty conditions. Due to their ability to measure distances with high precision, the radar sensors can also be used as altimeters when other sources of information such as barometers or GPS are not available or cannot operate optimally.

Drones play an increasingly important role in the area of logistics and services. Well-known logistic companies place great hope in these compact, aerial...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

International Tinnitus Conference of the Tinnitus Research Initiative in Regensburg

13.03.2018 | Event News

International Virtual Reality Conference “IEEE VR 2018” comes to Reutlingen, Germany

08.03.2018 | Event News

Latest News

Wandering greenhouse gas

16.03.2018 | Earth Sciences

'Frequency combs' ID chemicals within the mid-infrared spectral region

16.03.2018 | Physics and Astronomy

Biologists unravel another mystery of what makes DNA go 'loopy'

16.03.2018 | Life Sciences

Science & Research
Overview of more VideoLinks >>>