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

Physics

New technique uses fraction of measurements to efficiently find quantum wave functions August 28th, 2014

Creation of a Highly Efficient Technique to Develop Low-Friction Materials Which Are Drawing Attention in Association with Energy Issues August 26th, 2014

X-ray Laser Probes Tiny Quantum Tornadoes in Superfluid Droplets: SLAC Experiment Reveals Mysterious Order in Liquid Helium August 25th, 2014

Rice physicist emerges as leader in quantum materials research: Nevidomskyy wins both NSF CAREER Award and Cottrell Scholar Award August 20th, 2014

Graphene

Competition for Graphene: Berkeley Lab Researchers Demonstrate Ultrafast Charge Transfer in New Family of 2D Semiconductors August 26th, 2014

Graphene Structure Studied in Iran by Novel Method August 25th, 2014

Govt.-Legislation/Regulation/Funding/Policy

New analytical technology reveals 'nanomechanical' surface traits August 29th, 2014

New Vice President Takes Helm at CNSE CMOST: Catherine Gilbert To Lead CNSE Children’s Museum of Science and Technology Through Expansion And Relocation August 29th, 2014

Leading European communications companies and research organizations have launched an EU project developing the future 5th Generation cellular mobile networks August 28th, 2014

New technique uses fraction of measurements to efficiently find quantum wave functions August 28th, 2014

Discoveries

A new, tunable device for spintronics: An international team of scientists including physicist Jairo Sinova from the University of Mainz realises a tunable spin-charge converter made of GaAs August 29th, 2014

Nanoscale assembly line August 29th, 2014

Copper shines as flexible conductor August 29th, 2014

Novel 'butterfly' molecule could build new sensors, photoenergy conversion devices August 28th, 2014

Announcements

A new, tunable device for spintronics: An international team of scientists including physicist Jairo Sinova from the University of Mainz realises a tunable spin-charge converter made of GaAs August 29th, 2014

Nanoscale assembly line August 29th, 2014

New analytical technology reveals 'nanomechanical' surface traits August 29th, 2014

New Vice President Takes Helm at CNSE CMOST: Catherine Gilbert To Lead CNSE Children’s Museum of Science and Technology Through Expansion And Relocation August 29th, 2014

Military

Fonon Announces 3D Metal Sintering Technology: Emerging Additive Nano Powder Manufacturing Technology August 28th, 2014

New technique uses fraction of measurements to efficiently find quantum wave functions August 28th, 2014

Introducing the multi-tasking nanoparticle: Versatile particles offer a wide variety of diagnostic and therapeutic applications August 26th, 2014

Biomimetic photodetector 'sees' in color: Rice lab uses CMOS-compatible aluminum for on-chip color detection August 25th, 2014

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

Rice physicist emerges as leader in quantum materials research: Nevidomskyy wins both NSF CAREER Award and Cottrell Scholar Award August 20th, 2014

Oxford Instruments Asylum Research Receives the 2014 Microscopy Today Innovation Award for blueDrive Photothermal Excitation August 18th, 2014

AQUANOVA receives Technology Leadership Award 2014 FROST & SULLIVAN honors NovaSOL® Technology again August 12th, 2014

Focal blood-brain-barrier disruption with high-frequency pulsed electric fields August 12th, 2014

Photonics/Optics/Lasers

New analytical technology reveals 'nanomechanical' surface traits August 29th, 2014

Fonon Announces 3D Metal Sintering Technology: Emerging Additive Nano Powder Manufacturing Technology August 28th, 2014

Competition for Graphene: Berkeley Lab Researchers Demonstrate Ultrafast Charge Transfer in New Family of 2D Semiconductors August 26th, 2014

Symphony of nanoplasmonic and optical resonators leads to magnificent laser-like light emission August 26th, 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