Navigation Links
Researchers tune the strain in graphene drumheads to create quantum dots
Date:6/21/2012

Tightening or relaxing the tension on a drumhead will change the way the drum sounds. The same goes for drumheads made from graphene, only instead of changing the sound, stretching graphene has a profound effect on the material's electrical properties. Researchers working at the National Institute of Standards and Technology (NIST) and the University of Maryland have shown that subjecting graphene to mechanical strain can mimic the effects of magnetic fields and create a quantum dot, an exotic type of semiconductor with a wide range of potential uses in electronic devices.

The results were reported in the June 22, 2012, issue of Science.*

Graphene is a single layer of carbon atoms arranged in a honeycomb lattice. Able to conduct electricity with little resistance at room temperature, graphene is a prime candidate for applications ranging from flexible displays to high speed transistors.

However, the same lack of electrical resistance that makes graphene attractive for some uses also makes it ill-suited for digital computing applications. Graphene conducts electricity so well because it doesn't have a band gapan energetic threshold beneath which the material won't conduct electricity. This means that graphene can't be turned "off," and computers need "on" and "off" signals to transmit and process information.

Because substrates slow the speed of electrons moving through graphene, Nikolai Klimov, a University of Maryland postdoctoral researcher working at NIST, suspended the graphene over shallow holes in a substrate of silicon dioxideessentially making a set of graphene drumheads. To measure the graphene's properties, the team used a unique scanning probe microscope designed and built at NIST.

When they began to probe the drumheads, they found that the graphene rose up to meet the tip of the microscope a result of the van der Waals force, a weak electrical force that creates attraction between objects that are very close to each other.

"While our instrument was telling us that the graphene was shaped like a bubble clamped at the edges, the simulations run by our colleagues at the University of Maryland showed that we were only detecting the graphene's highest point," says NIST scientist Nikolai Zhitenev. "Their calculations showed that the shape was actually more like the shape you would get if you poke into the surface of an inflated balloon, like a teepee or circus tent."

The researchers discovered that they could tune the strain in the drumhead using the conducting plate upon which the graphene and substrate were mounted to create a countervailing attraction and pull the drumhead down. In this way, they could pull the graphene into or out of the hole below it. And their measurements showed that changing the degree of strain changed the material's electrical properties.

For instance, the group observed that when they pulled the graphene membrane into the tent-like shape, the region at the apex acted just like a quantum dot, a type of semiconductor in which electrons are confined to a small region of space.

Creating semiconducting regions like quantum dots in graphene by modifying its shape might give scientists the best of both worlds: high speed and the band gap crucial to computing and other applications.

According to Zhitenev, the electrons flow through graphene by following the segments of the hexagons. Stretching the hexagons lowers the energy near the apex of the tent-like shape and causes the electrons to move in closed, clover-shaped orbitsmimicking nearly exactly how the electrons would move in a vertically varied magnetic field.

"This behavior is really quite remarkable," says Zhitenev. "There is a little bit of electron leakage, but we found that if we complemented the pseudomagnetic field with an actual magnetic field, there was no leakage whatsoever."

"Normally, to make a graphene quantum dot, you would have to cut out a nanosize piece of graphene," says NIST Fellow Joseph Stroscio. "Our work shows that you can achieve the same thing with strain-induced pseudomagnetic fields. It's a great result, and a significant step toward developing future graphene-based devices."


'/>"/>
Contact: Mark Esser
mark.esser@nist.gov
301-975-8735
National Institute of Standards and Technology (NIST)
Source:Eurekalert

Related biology technology :

1. WHEATON® Introduces a New Web Community for Scientists, Researchers, and Biopharmaceutical Packagers
2. Stevenage Bioscience Catalyst to Welcome Cambridge University Researchers
3. Syracuse University researchers use nanotechnology to harness power of fireflies
4. Researchers discover hereditary enzyme deficiency
5. JCVI Researchers, as Part of NIH Human Microbiome Project Consortium, Publish Papers Detailing the Variety and Abundance of Microbes Living on and in the Human Body
6. Produce Safety Researchers Awarded by ABC Research Laboratories
7. CNIO researchers describe a new target for developing anti-angiogenic and anti-tumoral therapies
8. U of S researchers create powerful new tool for research and drug development
9. Researchers love triangles
10. Sensing the infrared: Researchers improve IR detectors with single-walled carbon nanotubes
11. Generex Enhances Antigen Express Scientific Advisory Board for the AE37 Breast Cancer Vaccine with Renowned Breast Cancer Researchers
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:12/8/2016)... ... December 08, 2016 , ... From ... innovation is taking over sports. On Thursday, December 15th a panel of entrepreneurs, ... disrupting the playing field at a Smart Talk session. Smart Talk will run ...
(Date:12/8/2016)... , Dec. 8, 2016 Eurofins announces the appointment of ... President of Eurofins Scientific Inc. (ESI). Mr. Murray ... proven professional and entrepreneurial experience in leading international business teams. As ... food testing market to uphold Eurofins, status as the global leader ... , ...
(Date:12/8/2016)... Oxford Gene Technology (OGT), ... panel range with the launch of the SureSeq myPanel™ NGS ... variants in familial hypercholesterolemia (FH). The panel delivers single nucleotide ... single small panel and allows customisation by ,mix and match, ... for LDLR , P C SK9 ...
(Date:12/8/2016)... San Francisco, CA (PRWEB) , ... December 08, ... ... and Oculus as finalists in the World Technology Awards. uBiome is one of ... were received across all categories. , In addition to uBiome, companies nominated as ...
Breaking Biology Technology:
(Date:11/29/2016)... Nearly one billion matches per second with DERMALOG,s ... ... DERMALOG is Germany's largest Multi-Biometric ... Management. (PRNewsFoto/DERMALOG Identification Systems) ... DERMALOG is Germany's largest Multi-Biometric supplier: The company's Fingerprint Identification System is ...
(Date:11/22/2016)... According to the new market research report "Biometric System Market by Authentication ... (Hardware and Software), Function (Contact and Non-contact), Application, and Region - Global ... from USD 10.74 Billion in 2015 to reach USD 32.73 Billion by ... Continue Reading ... ...
(Date:11/19/2016)... , Nov. 18, 2016 Securus Technologies, ... solutions for public safety, investigation, corrections and monitoring, announced ... smaller competitor, ICSolutions, to have an independent technology judge ... the most modern high tech/sophisticated telephone calling platform, and ... customers that they do most of what we do ...
Breaking Biology News(10 mins):