Nanotechnology Now







Heifer International

Wikipedia Affiliate Button


DHgate

Home > Press > Graphene exhibits bizarre new behavior well-suited to electronic devices

Scanning tunneling microscope image of a single layer of graphene on platinum with four nanobubbles at the graphene-platinum border and one in the patch interior. The inset shows a high-resolution image of a graphene nanobubble and its distorted honeycomb lattice due to strain in the bubble. (Crommie lab, UC Berkeley image)
Scanning tunneling microscope image of a single layer of graphene on platinum with four nanobubbles at the graphene-platinum border and one in the patch interior. The inset shows a high-resolution image of a graphene nanobubble and its distorted honeycomb lattice due to strain in the bubble. (Crommie lab, UC Berkeley image)

Abstract:
Graphene, a sheet of pure carbon heralded as a possible replacement for silicon-based semiconductors, has been found to have a unique and amazing property that could make it even more suitable for future electronic devices.

Graphene exhibits bizarre new behavior well-suited to electronic devices

Berkeley, CA | Posted on July 30th, 2010

Physicists at the University of California, Berkeley, and the Lawrence Berkeley National Laboratory (LBNL) have found that when graphene is stretched in a specific way it sprouts nanobubbles in which electrons behave in a bizarre way, as if they are moving in a strong magnetic field.

Specifically, the electrons within each nanobubble segregate into quantized energy levels instead of occupying energy bands, as in unstrained graphene. The energy levels are identical to those that an electron would occupy if it were moving in circles in a very strong magnetic field, as high as 300 tesla, which is bigger than any laboratory can produce except in brief explosions, said Michael Crommie, professor of physics at UC Berkeley and a faculty researcher at LBNL. Magnetic resonance imagers use magnets less than 10 tesla, while the Earth's magnetic field at ground level is 31 microtesla.

"This gives us a new handle on how to control how electrons move in graphene, and thus to control graphene's electronic properties, through strain," Crommie said. "By controlling where the electrons bunch up and at what energy, you could cause them to move more easily or less easily through graphene, in effect, controlling their conductivity, optical or microwave properties. Control of electron movement is the most essential part of any electronic device."

Crommie and colleagues report the discovery in the July 30 issue of the journal Science.

Aside from the engineering implications of the discovery, Crommie is eager to use this unusual property of graphene to explore how electrons behave in fields that until now have been unobtainable in the laboratory.

"When you crank up a magnetic field you start seeing very interesting behavior because the electrons spin in tiny circles," he said. "This effect gives us a new way to induce this behavior, even in the absence of an actual magnetic field."

Among the unusual behaviors observed of electrons in strong magnetic fields are the quantum Hall effect and the fractional quantum Hall effect, where at low temperatures electrons also fall into quantized energy levels.

The new effect was discovered by accident when a UC Berkeley postdoctoral researcher and several students in Crommie's lab grew graphene on the surface of a platinum crystal. Graphene is a one atom-thick sheet of carbon atoms arranged in a hexagonal pattern, like chicken wire. When grown on platinum, the carbon atoms do not perfectly line up with the metal surface's triangular crystal
structure, which creates a strain pattern in the graphene as if it were being pulled from three different directions.

The strain produces small, raised triangular graphene bubbles 4 to 10 nanometers across in which the electrons occupy discrete energy levels rather than the broad, continuous range of energies allowed by the band structure of unstrained graphene. This new electronic behavior was detected spectroscopically by scanning tunneling microscopy. These so-called Landau levels are reminiscent of the quantized energy levels of electrons in the simple Bohr model of the atom, Crommie said.

The appearance of a pseudomagnetic field in response to strain in graphene was first predicted for carbon nanotubes in 1997 by Charles Kane and Eugene Mele of the University of Pennsylvania. Nanotubes are a rolled up form of graphene.

Within the last year, however, Francisco Guinea of the Instituto de Ciencia de Materiales de Madrid in Spain, Mikhael Katsnelson of Radboud University of Nijmegen, the Netherlands, and A. K. Geim of the University of Manchester, England predicted what they termed a pseudo quantum Hall effect in strained graphene . This is the very quantization that Crommie's research group has experimentally observed. Boston University physicist Antonio Castro Neto, who was
visiting Crommie's laboratory at the time of the discovery, immediately recognized the implications of the data, and subsequent experiments confirmed that it reflected the pseudo quantum Hall effect predicted earlier.

"Theorists often latch onto an idea and explore it theoretically even before the experiments are done, and sometimes they come up with predictions that seem a little crazy at first. What is so exciting now is that we have data that shows these ideas are not so crazy," Crommie said. "The observation of these giant pseudomagnetic fields opens the door to room-temperature 'straintronics,' the idea of using mechanical deformations in graphene to engineer its behavior for different electronic device applications."

Crommie noted that the "pseudomagnetic fields" inside the nanobubbles are so high that the energy levels are separated by hundreds of millivolts, much higher than room temperature. Thus, thermal noise would not interfere with this effect in graphene even at room temperature. The nanobubble experiments performed in Crommie's laboratory, however, were performed at very low temperature.

Normally, electrons moving in a magnetic field circle around the field lines. Within the strained nanobubbles, the electrons move in circles in the plane of the graphene sheet, as if a strong magnetic field has been applied perpendicular to the sheet even when there is no actual
magnetic field. Apparently, Crommie said, the pseudomagnetic field only affects moving electrons and not other properties of the electron, such as spin, that are affected by real magnetic fields.

Other authors of the report, in addition to Crommie, Castro Neto and Guinea, are Sarah Burke, now a professor at the University of British Columbia; Niv Levy, now a postdoctoral researcher at the National Institute of Technology and Standards; and graduate student Kacey L. Meaker, undergraduate Melissa Panlasigui and physics professor Alex Zettl of UC Berkeley.

The research was funded through the U.S. Department of Energy Office of Science and the U.S. Office of Naval Research.

####

For more information, please click here

Contacts:
SOURCE:
Michael Crommie
(510) 642-9392


Robert Sanders
(510) 643-6998

Copyright © University of California, Berkeley

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 News Press

News and information

A first glimpse inside a macroscopic quantum state March 28th, 2015

DFG to Establish One Clinical Research Unit and Five Research Units: New Projects to Investigate Complications in Pregnancy, Particle Physics, Nanoparticles, Implants and Transport Planning / Approximately 13 Million Euros in Funding for an Initial Three-Year Period March 28th, 2015

Chemists make new silicon-based nanomaterials March 27th, 2015

UT Dallas engineers twist nanofibers to create structures tougher than bulletproof vests March 27th, 2015

Govt.-Legislation/Regulation/Funding/Policy

UT Dallas engineers twist nanofibers to create structures tougher than bulletproof vests March 27th, 2015

Novel nanoparticle therapy promotes wound healing March 27th, 2015

Designer's toolkit for dynamic DNA nanomachines: Arm-waving nanorobot signals new flexibility in DNA origami March 27th, 2015

Using magnetic fields to understand high-temperature superconductivity: Los Alamos explores experimental path to potential 'next theory of superconductivity' March 27th, 2015

Possible Futures

Nanotechnology in Medical Devices Market is expected to reach $8.5 Billion by 2019 March 25th, 2015

Nanotechnology Enabled Drug Delivery to Influence Future Diagnosis and Treatments of Diseases March 21st, 2015

Nanocomposites Market Growth, Industry Outlook To 2020 by Grand View Research, Inc. March 21st, 2015

Nanotechnology Drug Delivery Market in the US 2012-2016 : Latest Report Available by Radiant Insights, Inc March 16th, 2015

Academic/Education

LAMDAMAP 2015 hosted by the University March 26th, 2015

SUNY Poly & M+W Make Major Announcement: Major Expansion To Include M+W Owned Gehrlicher Solar America Corporation That Will Create up to 400 Jobs to Develop Solar Power Plants at SUNY Poly Sites Across New York State March 26th, 2015

SUNY POLY CNSE to Host First Ever Northeast Semi Supply Conference (NESCO) Conference Will Connect New and Emerging Innovators in the Northeastern US and Canada with Industry Leaders and Strategic Investors to Discuss Future Growth Opportunities in NYS March 25th, 2015

FEI Joins University of Ulm and CEOS on SALVE Project Research Collaboration: The Sub-Ångström Low Voltage Electron (SALVE) microscope should improve contrast and reduce damage on bio-molecules and two-dimensional nanomaterials, such as graphene March 18th, 2015

Nanotubes/Buckyballs

Carbon nanotube fibers make superior links to brain: Rice University invention provides two-way communication with neurons March 25th, 2015

Iranian Scientists Eliminate Expensive Materials from Diabetes Diagnosis Sensors March 25th, 2015

Effect of Carbon Nanotubes on Properties of Cement Composites Studied in Iran March 23rd, 2015

First proof of isolated attosecond pulse generation at the carbon K-edge March 20th, 2015

Discoveries

A first glimpse inside a macroscopic quantum state March 28th, 2015

UT Dallas engineers twist nanofibers to create structures tougher than bulletproof vests March 27th, 2015

Novel nanoparticle therapy promotes wound healing March 27th, 2015

Designer's toolkit for dynamic DNA nanomachines: Arm-waving nanorobot signals new flexibility in DNA origami March 27th, 2015

Announcements

A first glimpse inside a macroscopic quantum state March 28th, 2015

DFG to Establish One Clinical Research Unit and Five Research Units: New Projects to Investigate Complications in Pregnancy, Particle Physics, Nanoparticles, Implants and Transport Planning / Approximately 13 Million Euros in Funding for an Initial Three-Year Period March 28th, 2015

Designer's toolkit for dynamic DNA nanomachines: Arm-waving nanorobot signals new flexibility in DNA origami March 27th, 2015

Using magnetic fields to understand high-temperature superconductivity: Los Alamos explores experimental path to potential 'next theory of superconductivity' March 27th, 2015

Research partnerships

SUNY Poly & M+W Make Major Announcement: Major Expansion To Include M+W Owned Gehrlicher Solar America Corporation That Will Create up to 400 Jobs to Develop Solar Power Plants at SUNY Poly Sites Across New York State March 26th, 2015

ORNL-led team demonstrates desalination with nanoporous graphene membrane March 25th, 2015

New kind of 'tandem' solar cell developed: Researchers combine 2 types of photovoltaic material to make a cell that harnesses more sunlight March 24th, 2015

UW scientists build a nanolaser using a single atomic sheet March 24th, 2015

Quantum nanoscience

Using magnetic fields to understand high-temperature superconductivity: Los Alamos explores experimental path to potential 'next theory of superconductivity' March 27th, 2015

Thousands of atoms entangled with a single photon: Result could make atomic clocks more accurate March 26th, 2015

Bar-Ilan U. researchers identify 'tipping point' between quantum and classical worlds: Study sheds new light on 'spooky' quantum optics March 24th, 2015

Nanospheres cooled with light to explore the limits of quantum physics March 17th, 2015

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




  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More










ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project







© Copyright 1999-2015 7th Wave, Inc. All Rights Reserved PRIVACY POLICY :: CONTACT US :: STATS :: SITE MAP :: ADVERTISE