Featured Research

from universities, journals, and other organizations

Visualizing Atomic-scale Acoustic Waves In Nanostructures

Date:
July 7, 2008
Source:
DOE/Lawrence Livermore National Laboratory
Summary:
Acoustic waves play many everyday roles -- from communication between people to ultrasound imaging. Now the highest frequency acoustic waves in materials, with nearly atomic-scale wavelengths, promise to be useful probes of nanostructures such as LED lights.

Electromagnetic radiation is produced when an acoustic wave (purple) generates electric currents (red) as it propagates past an interface between two piezoelectric materials. The radiation propagates outside of the materials and can be detected to determine the shape of the acoustic wave with nearly atomic scale resolution.
Credit: Image courtesy of DOE/Lawrence Livermore National Laboratory

Acoustic waves play many everyday roles - from communication between people to ultrasound imaging. Now the highest frequency acoustic waves in materials, with nearly atomic-scale wavelengths, promise to be useful probes of nanostructures such as LED lights.

However, detecting them isn't so easy.

Enter Lawrence Livermore National Laboratory scientists, who discovered a new physical phenomenon that enables them to see high frequency waves by combining molecular dynamics simulations of shock waves with an experimental diagnostic, terahertz (THz) radiation. (The hertz is the base unit of frequency. One hertz simply means one cycle per second. A terahertz is 1012 hertz.).

The Livermore scientists performed computer simulations of the highest frequency acoustic waves forming spontaneously at the front of shock waves or generated by sub-picosecond pulse-length lasers.

They discovered that, under some circumstances, when such a wave crosses an interface between two materials, tiny electric currents are generated at the interface. These currents produce electromagnetic radiation of THz frequencies that can be detected a few millimeters away from the interface. Part of the wave is effectively converted to electromagnetic radiation, which propagates out of the material where it can be measured.

Most molecular dynamics simulations of shock waves connect to experiments through electronic properties, such as optical reflectivity.

"But this new approach connects to the much lower frequency THz radiation produced by the individual atoms moving around in the shock wave," said Evan Reed, lead author of a paper that appears in the July 7 edition of the journal, Physical Review Letters. "This kind of diagnostic promises to provide new information about shocked materials like the dynamics of crystals pushed to ultra-high strain rates."

Using molecular dynamics simulations, the team, made up of Livermore's Reed and Michael Armstrong in collaboration with Los Alamos National Laboratory colleagues shows that the time-history of the wave can be determined with potentially sub-picosecond, nearly atomic time and space resolution by measuring the electromagnetic field.

Reed and colleagues studied the effect for an interface between two thin films, which are used in LED (light-emitting diode) nanostructures, and are piezoelectric (electric currents that are generated when they are squeezed). Piezoelectric materials have been used for decades as arrival time gauges for shock-wave experiments but have been limited by electrical equipment that can only detect acoustic frequencies less than 10 gigathertz (GHz), precluding observation of the highest frequency acoustic waves. The new THz radiation technique can help improve the time resolution of such approaches.

The technique has other applications as well. It can be applied to determine the structure of many kinds of electronic devices that are constructed using thin film layered structures, such as field-effect transistors.

"The detection of high frequency acoustic waves also has been proposed for use in imaging of quantum dot nanostructures used in myriad optical devices, possibly including solar cells in the future," Reed said. "The technology is not there yet for that application, but our work represents a step closer."


Story Source:

The above story is based on materials provided by DOE/Lawrence Livermore National Laboratory. Note: Materials may be edited for content and length.


Cite This Page:

DOE/Lawrence Livermore National Laboratory. "Visualizing Atomic-scale Acoustic Waves In Nanostructures." ScienceDaily. ScienceDaily, 7 July 2008. <www.sciencedaily.com/releases/2008/07/080703160751.htm>.
DOE/Lawrence Livermore National Laboratory. (2008, July 7). Visualizing Atomic-scale Acoustic Waves In Nanostructures. ScienceDaily. Retrieved April 21, 2014 from www.sciencedaily.com/releases/2008/07/080703160751.htm
DOE/Lawrence Livermore National Laboratory. "Visualizing Atomic-scale Acoustic Waves In Nanostructures." ScienceDaily. www.sciencedaily.com/releases/2008/07/080703160751.htm (accessed April 21, 2014).

Share This



More Matter & Energy News

Monday, April 21, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Why Did Nike Fire Most Of Its Nike FuelBand Team?

Why Did Nike Fire Most Of Its Nike FuelBand Team?

Newsy (Apr. 19, 2014) Nike fired most of its Digital Sport hardware team, the group behind Nike's FuelBand device. Could Apple or an overcrowded market be behind layoffs? Video provided by Newsy
Powered by NewsLook.com
Small Reactors Could Be Future of Nuclear Energy

Small Reactors Could Be Future of Nuclear Energy

AP (Apr. 17, 2014) After the Fukushima nuclear disaster, the industry fell under intense scrutiny. Now, small underground nuclear power plants are being considered as the possible future of the nuclear energy. (April 17) Video provided by AP
Powered by NewsLook.com
Horseless Carriage Introduced at NY Auto Show

Horseless Carriage Introduced at NY Auto Show

AP (Apr. 17, 2014) An electric car that proponents hope will replace horse-drawn carriages in New York City has also been revealed at the auto show. (Apr. 17) Video provided by AP
Powered by NewsLook.com
Honda's New ASIMO Robot, More Human-Like Than Ever

Honda's New ASIMO Robot, More Human-Like Than Ever

AFP (Apr. 17, 2014) It walks and runs, even up and down stairs. It can open a bottle and serve a drink, and politely tries to shake hands with a stranger. Meet the latest ASIMO, Honda's humanoid robot. Duration: 00:54 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins