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:6/16/2017)... ... 2017 , ... Cognition Corporation , a software company ... of its “From the Helm” Webinar Series. , The next two free ... design control exercises. Led by David Cronin, Cognition’s CEO, the half-hour public webinars ...
(Date:6/16/2017)... (PRWEB) , ... June 16, 2017 , ... CTNext ... Entrepreneur Innovation Awards (EIA), held at The LOFT at Chelsea Piers in Stamford. , ... ideas to a panel of judges for an opportunity to secure $10,000 awards to ...
(Date:6/15/2017)... ... June 15, 2017 , ... ... secured a Series B round of financing in the amount of $6 million. ... private investors participated in the round. , The Series B funding will enable ...
(Date:6/15/2017)... , ... June 15, 2017 , ... ... a promising new medical device startup. Dan Parsley, angelMD’s SVP of Corporate Development, ... members, and this angelMD syndicate is part of Saranas’ recently announced $4 million ...
Breaking Biology Technology:
(Date:5/23/2017)... robotic gym for the rehabilitation and functional motor sense evaluation of lower ... . The first 30 robots will be available from June in ... The technology was developed and patented at the IIT laboratories and has ... to a 10 million euro investment from entrepreneur Sergio Dompè. ... ...
(Date:5/6/2017)... 2017 RAM Group , Singaporean ... breakthrough in biometric authentication based on a ... to perform biometric authentication. These new sensors are based ... by Ram Group and its partners. This sensor will ... chains and security. Ram Group is a next ...
(Date:4/18/2017)... 18, 2017  Socionext Inc., a global expert in SoC-based imaging ... server, the M820, which features the company,s hybrid codec technology. A ... Tera Probe, Inc., will be showcased during the upcoming Medtec Japan ... at the Las Vegas Convention Center April ... Click here for ...
Breaking Biology News(10 mins):