Nanotechnology Now

Our NanoNews Digest Sponsors





Heifer International

Wikipedia Affiliate Button


android tablet pc

Home > Press > Experiments bolster theory of how electrons cool in graphene

Matt Graham
An illustration of how a heated electron cools in graphene. The electron slowly cools by emitting regular phonons, illustrated by zigzags down a Dirac Cone (a visualization of graphene's electronic band structure). When the electron hits a defect, it bounces off the lattice - a "supercollision" - which speeds up the cooling process.
Matt Graham

An illustration of how a heated electron cools in graphene. The electron slowly cools by emitting regular phonons, illustrated by zigzags down a Dirac Cone (a visualization of graphene's electronic band structure). When the electron hits a defect, it bounces off the lattice - a "supercollision" - which speeds up the cooling process.

Abstract:
It's a basic tenet of physics that scientists are trying to explain in graphene, single-atom thick sheets of carbon: When electrons are excited, or heated, how quickly do they relax, or cool?

Experiments bolster theory of how electrons cool in graphene

Ithaca, NY | Posted on December 3rd, 2012

A research team supported by the Kavli Institute at Cornell for Nanoscale Science has shed some light on the topic through the first known direct measurements of hot electrons cooling down in graphene.

The team, which published its findings online Dec. 2 in the journal Nature Physics, includes lead researcher Paul McEuen, the Kavli Institute director and Goldwin Smith Professor of Physics; first author Matt Graham, a Kavli postdoctoral fellow; and co-authors Jiwoong Park, assistant professor of chemistry and chemical biology and Kavli member; Dan Ralph, Horace White Professor of Physics and Kavli member; and Su-Fei Shen, Ralph's former graduate student.

When electrons travel through graphene, they create a quantum lattice vibration, called a phonon. In doing so, the difference in energy the electron emits must equal the amount gained by the phonon; this is the "cooling" that happens as the system is returning to its equilibrium state, and this movement of electrons is at the heart of understanding how electronic devices work.

The new Cornell experiment supports a previous theory that electrons in graphene experience "supercollisions" as they cool -- they bump into defects in the crystal lattice, imparting their momentum to the defects, thereby making the cooling process much faster than if the graphene were a perfectly repeating crystal.

"The remarkable thing about the theory was it predicted all kinds of details, and it got it all right," McEuen said.

Watching electrons move through graphene took some novel experimental legwork. Graham and colleagues conceived a setup in which they shot very short laser pulses -- about 100 femtoseconds apart -- at a piece of conventionally grown graphene.

They observed the temperature of the graphene as it heated and cooled at a p-n junction, which is the interface at which electrons travel between two semiconductors. By tracking the magnitude of the current passing through the junction, they essentially used the junction as a tiny thermometer.

Heating the junction with an initial laser pulse, they hit it with a second pulse at specific time delays, comparing the crossover of temperatures. This technique allowed the team to measure the temperature of the system with sub-picosecond time resolution and within a few kelvins of accuracy. Their results agreed very well with the supercollision theory of the rate at which electrons cool in graphene.

The results provide further insights into the fundamental nature of graphene so it can one day be used in anything from photodetectors to non-silicon transistors, McEuen said. It is already well known that graphene shows promise for next-generation electronics because of its near-perfect conductivity, transparency and tensile strength.

The work was supported by the Kavli Institute, the National Science Foundation through the Center for Nanoscale Systems, the MARCO Focused Research Center on Materials, Structures and Devices, and the Air Force Office of Scientific Research.

####

For more information, please click here

Contacts:
Media Contact:
Syl Kacapyr
(607) 255-7701


Cornell Chronicle:
Anne Ju
(607) 255-9735

Copyright © Cornell University

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

Graphene

Silicene Labs Announces the Launch of Patent-Pending, 2D Materials Composite Index™ : The Initial 2D Materials Composite Index™ for Q2 2014 Is: 857.3; Founders Include World-Renowned Physicist and Seasoned Business and IP Professionals July 24th, 2014

Penn Study: Understanding Graphene’s Electrical Properties on an Atomic Level July 22nd, 2014

Haydale and Goodfellow Announce Major Distribution Agreement for Functionalised Graphene Materials July 21st, 2014

CIQUS researchers develop an extremely simple procedure to obtain nanosized graphenes July 15th, 2014

Researchers discover boron 'buckyball' July 14th, 2014

Physics

Physicists Use Computer Models to Reveal Quantum Effects in Biological Oxygen Transport: The team solved a long-standing question by explaining why oxygen – and not deadly carbon monoxide – preferably binds to the proteins that transport it around the body. July 17th, 2014

Flashes of light on the superconductor: Using light to modulate the properties of a copper-based superconductor July 15th, 2014

Govt.-Legislation/Regulation/Funding/Policy

NNCO Announces an Interactive Webinar: Progress Review on the Coordinated Implementation of the National Nanotechnology Initiative 2011 Environmental, Health, and Safety Research Strategy July 23rd, 2014

Nano-sized Chip "Sniffs Out" Explosives Far Better than Trained Dogs: TAU researcher's groundbreaking sensor detects miniscule concentrations of hazardous materials in the air July 23rd, 2014

NIST shows ultrasonically propelled nanorods spin dizzyingly fast July 22nd, 2014

Penn Study: Understanding Graphene’s Electrical Properties on an Atomic Level July 22nd, 2014

Discoveries

Iranian Scientists Produce Transparent Nanocomposite Coatings with Longer Lifetime July 24th, 2014

UCF Nanotech Spinout Developing Revolutionary Battery Technology: Power the Next Generation of Electronics with Carbon July 23rd, 2014

A Crystal Wedding in the Nanocosmos July 23rd, 2014

Nano-sized Chip "Sniffs Out" Explosives Far Better than Trained Dogs: TAU researcher's groundbreaking sensor detects miniscule concentrations of hazardous materials in the air July 23rd, 2014

Announcements

Silicene Labs Announces the Launch of Patent-Pending, 2D Materials Composite Index™ : The Initial 2D Materials Composite Index™ for Q2 2014 Is: 857.3; Founders Include World-Renowned Physicist and Seasoned Business and IP Professionals July 24th, 2014

Iranian Scientists Produce Transparent Nanocomposite Coatings with Longer Lifetime July 24th, 2014

Deadline Announced for Registration in 7th Int'l Nanotechnology Festival in Iran July 23rd, 2014

A Crystal Wedding in the Nanocosmos July 23rd, 2014

Military

Nano-sized Chip "Sniffs Out" Explosives Far Better than Trained Dogs: TAU researcher's groundbreaking sensor detects miniscule concentrations of hazardous materials in the air July 23rd, 2014

Carbyne morphs when stretched: Rice University calculations show carbon-atom chain would go metal to semiconductor July 21st, 2014

Tiny laser sensor heightens bomb detection sensitivity July 19th, 2014

Future Electronics May Depend on Lasers, Not Quartz July 17th, 2014

Grants/Awards/Scholarships/Gifts/Contests/Honors/Records

Hysitron is Awarded TWO R&D 100 Awards for Highly Innovative Technology Developments in the Areas of Extreme Environments and Biological Mechanical Property Testing July 23rd, 2014

Researchers create vaccine for dust-mite allergies Main Page Content: Vaccine reduced lung inflammation to allergens in lab and animal tests July 22nd, 2014

EPFL Research on the use of AFM based nanoscale IR spectroscopy for the study of single amyloid molecules wins poster competition at Swiss Physics Society meeting July 22nd, 2014

Carbyne morphs when stretched: Rice University calculations show carbon-atom chain would go metal to semiconductor July 21st, 2014

Photonics/Optics/Lasers

NUS scientists use low cost technique to improve properties and functions of nanomaterials: By 'drawing' micropatterns on nanomaterials using a focused laser beam, scientists could modify properties of nanomaterials for effective applications in photonic and optoelectric applicat July 22nd, 2014

Carbyne morphs when stretched: Rice University calculations show carbon-atom chain would go metal to semiconductor July 21st, 2014

Tiny laser sensor heightens bomb detection sensitivity July 19th, 2014

Future Electronics May Depend on Lasers, Not Quartz July 17th, 2014

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 1999-2014 7th Wave, Inc. All Rights Reserved PRIVACY POLICY :: CONTACT US :: STATS :: SITE MAP :: ADVERTISE