Featured Research

from universities, journals, and other organizations

Newly Discovered Properties Of Certain Crystals Could Impact The Miniaturization Of Electronic Devices

Date:
December 28, 2007
Source:
Forschungsverbund Berlin e.V.
Summary:
The dashing start of electrons in a crystal does not remain without consequences for their further fate. Researchers examined the ultrafast movement of electrons in a gallium arsenide crystal exposed for a short time to a very high electrical field. This conceptually new experiment shows for the first time a collective, oscillatory motion of the electrons with ultrahigh frequency, which arises additionally to the well-known drift motion of these particles. This newly discovered effect could play an important role in connection with the miniaturization of electronic devices.

The figure shows the self-induced potential of a moving electron and the distortion (schematic) of the crystal lattice.
Credit: MBI

The dashing start of electrons in a crystal does not remain without consequences for their further fate. Researchers examined the ultrafast movement of electrons in a gallium arsenide crystal exposed for a short time to a very high electrical field. This conceptually new experiment shows for the first time a collective, oscillatory motion of the electrons with ultrahigh frequency, which arises additionally to the well-known drift motion of these particles. This newly discovered effect could play an important role in connection with the miniaturization of electronic devices.

Related Articles


This is reported by the Berlin researchers Peter Gaal, Wilhelm Kuehn, Klaus Reimann, Michael Woerner, and Thomas Elsaesser of the Max-Born Institute and Rudolf Hey of the Paul Drude Institute in Nature*.

Gallium arsenide (GaAs) is one of the most important materials for semiconductor optoelectronics. A GaAs crystal consists of a regular lattice of gallium and arsenic atoms, in which the gallium atoms carry a small positive and the arsenic atoms a small negative electric charge. An electron moving slowly through the crystal causes in its neighbourhood a distortion of the crystal lattice. The negative electric charge of the electron repels negatively charged atoms and attracts positively charged atoms.

This causes oscillations of the atoms around their rest position: Lattice vibrations, so called phonons, develop. “That is similar to a heavy ball rolling over a mattress”, describes Michael Wφrner. “The metal springs of the mattress are squeezed together and relax again.” By the generation of lattice vibrations, the electrons lose energy and thus are slowed down. This deceleration is nothing else but the electrical resistance. The electrons drift with constant velocity through the lattice. This physical picture is the basis of the long-known law for the electrical resistance, Ohm’s law.

A completely new situation arises if the electrons experience a dashing start, i.e., if they are—by an extremely high electrical field—accelerated faster than the response time of the atoms in their neighbourhood. The Berlin researchers use for this strong acceleration an electrical field of 2 million Volts per meter, which is applied to the crystal for the extremely short duration of 0.3 picoseconds (1 picosecond is a millionth of a millionth of a second).

The motion of the electrons caused by this high electric field is observed with ultrashort light pulses in the infrared spectral region. In contrast to the drift motion with constant velocity observed for small electrical fields, for high fields the velocity of the accelerated electrons changes periodically between high and low values. The frequency of these velocity oscillations corresponds exactly to the highest frequency with which the atoms can vibrate, the frequency of so-called longitudinal optical phonons.

Theoretical computations confirmed quantitatively this experimentally found behaviour. MBI director Professor Thomas Elsaesser says, “the fact that strongly accelerated electrons can excite vibrations of the atoms and that in turn they are decelerated and accelerated by the vibrating atoms is of great importance for the charge transfer in nanostructures.” In such nanostructures, electrical fields of similar size can arise due to the small dimensions. Elsaesser adds: “Therefore our results are important for the optimization of transportation characteristics of semiconductor nanostructures.”

*Nature. Vol. 450, Page 1210.


Story Source:

The above story is based on materials provided by Forschungsverbund Berlin e.V.. Note: Materials may be edited for content and length.


Cite This Page:

Forschungsverbund Berlin e.V.. "Newly Discovered Properties Of Certain Crystals Could Impact The Miniaturization Of Electronic Devices." ScienceDaily. ScienceDaily, 28 December 2007. <www.sciencedaily.com/releases/2007/12/071221182423.htm>.
Forschungsverbund Berlin e.V.. (2007, December 28). Newly Discovered Properties Of Certain Crystals Could Impact The Miniaturization Of Electronic Devices. ScienceDaily. Retrieved January 30, 2015 from www.sciencedaily.com/releases/2007/12/071221182423.htm
Forschungsverbund Berlin e.V.. "Newly Discovered Properties Of Certain Crystals Could Impact The Miniaturization Of Electronic Devices." ScienceDaily. www.sciencedaily.com/releases/2007/12/071221182423.htm (accessed January 30, 2015).

Share This


More From ScienceDaily



More Matter & Energy News

Friday, January 30, 2015

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Nanoscale Sensor Could Help Wine Producers and Clinical Scientists

Nanoscale Sensor Could Help Wine Producers and Clinical Scientists

Reuters - Innovations Video Online (Jan. 30, 2015) — A nanosensor that mimics the oral effects and sensations of drinking wine has been developed by Danish and Portuguese researchers. Jim Drury saw it in operation. Video provided by Reuters
Powered by NewsLook.com
Tesla 'Insane Mode' Gives Unsuspecting Passengers the Ride of Their Life

Tesla 'Insane Mode' Gives Unsuspecting Passengers the Ride of Their Life

RightThisMinute (Jan. 29, 2015) — If your car has an "Insane Mode" then you know it&apos;s fast. Well, these unsuspecting passengers were in for one insane ride when they hit the button. Tesla cars are awesome. Video provided by RightThisMinute
Powered by NewsLook.com
Now Bill Gates Is 'Concerned' About Artificial Intelligence

Now Bill Gates Is 'Concerned' About Artificial Intelligence

Newsy (Jan. 29, 2015) — Bill Gates joins the list of tech moguls scared of super-intelligent machines. He says more people should be concerned, but why? Video provided by Newsy
Powered by NewsLook.com
Senate Passes Bill for Keystone XL Pipeline

Senate Passes Bill for Keystone XL Pipeline

AP (Jan. 29, 2015) — The Republican-controlled Senate has passed a bipartisan bill approving construction of the Keystone XL oil pipeline. (Jan. 29) Video provided by AP
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:

Strange & Offbeat Stories

 

Space & Time

Matter & Energy

Computers & Math

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