Featured Research

from universities, journals, and other organizations

Scientists Use Electron Beam To Unravel The Secrets Of An 'Atomic Switch'

Date:
August 18, 2006
Source:
National Institute of Standards and Technology
Summary:
Scientists at the Commerce Department's National Institute of Standards and Technology (NIST) have used a beam of electrons to move a single atom in a small molecule back and forth between two positions on a crystal surface, a significant step toward learning how to build an "atomic switch" that turns electrical signals on and off in nanoscale devices. The results, described in the Aug. 18, 2006, issue of Science.

NIST researchers used a scanning tunneling microscope (STM) to move a single cobalt atom (blue sphere) in a small molecule back and forth between two positions on a crystal surface. Based on measurements of the "noise" made by the molecule at each pixel of a topographical image made with the STM, the researchers made a computer-generated spatial map of the atom switching speed and probability, showing that switching is most likely when the STM tip is positioned to the left of the cobalt atom.
Credit: J.A. Stroscio, J.N. Crain, and R.J. Celotta, NIST

Scientists at the Commerce Department's National Institute of Standards and Technology (NIST) have used a beam of electrons to move a single atom in a small molecule back and forth between two positions on a crystal surface, a significant step toward learning how to build an "atomic switch" that turns electrical signals on and off in nanoscale devices.

The results, described in the Aug. 18, 2006, issue of Science,* are the first to be published about work at NIST's new Center for Nanoscale Science and Technology.

"It's still futuristic to talk about a real atomic switch but we're getting closer," says physicist Joseph Stroscio, lead author of the paper. In addition, by applying the findings to nanoscale fabrication on semiconductors and insulating thin films, it may be possible to develop new classes of electronic and magnetic devices constructed atom by atom.

In the work described in Science, NIST physicists used a custom-built, cryogenic scanning tunneling microscope (STM)--which provides a voltage and beam of electrons at its needle-like tip--to perform several different types of atomic scale measurements and manipulations. NIST theorists performed calculations of the atoms' electronic structure, which confirmed the experimental results.

A molecular chain of one cobalt atom and several copper atoms set upon a surface of copper atoms was constructed atom by atom using the STM in an atom manipulation mode. Then the STM was used to shoot electrons at the molecular chain and its effect on the switching motion of the cobalt atom was measured.

In addition, the team used a "tunneling noise spectroscopy" technique to determine how long the atom stays in one place. This measurement method was developed by two of the authors based on their 2004 discovery that an atom emits a characteristic scratching sound when an STM is used to move the atom between two types of bonding sites on a crystal**.

"The two most important new findings," Stroscio says, "are an increased understanding of the science behind atomic switching and the development of a new measurement capability to spatially map the probability of an electron exciting the desired atom motion."

The scientists analyzed what happened to the atom switching rate as changes occurred in the STM voltage and in the current between the STM tip and surface. Above a threshold voltage of about 15-20 millivolts, the probability for switching per electron is constant, meaning that the electrons contain sufficient energy to move the cobalt atom. Higher currents result in faster switching.

The data suggested that a single electron boosts the molecule above a critical energy level, allowing a key bond to break so the cobalt atom can switch positions. The cobalt atom was less likely to switch as the molecular chain was extended in length from two to five copper atoms, demonstrating that the atom switching dynamics can be tuned through changes in the molecular architecture.

The researchers also found that the position of the STM tip is critical. They made this discovery by recording detailed noise measurements of the molecule with atomic scale resolution. An analysis of the noise enabled the team to make a spatial map of the switching speed and probability, showing that switching is most likely when the STM tip is positioned to the left of the cobalt atom. This finding is consistent with calculations of electronic structure and demonstrates the need to inject energy into a particular bond, according to the paper.

"This insight raises the possibility that molecular orbital analysis may be used to guide the design and control of single atom manipulation in nanostructures," the authors write.

The work was supported in part by the Office of Naval Research.

*J.A. Stroscio, F. Tavazza, J.N. Crain, R.J. Celotta, and Anne M. Chaka. Electronically Induced Atom Motion in Engineered CoCun Nanostructures. Science. Aug. 18, 2006.

**J.A. Stroscio and R.J. Celotta. Controlling the Dynamics of a Single Atom in Lateral Atom Manipulation. Science Express, Sept. 9, 2004.


Story Source:

The above story is based on materials provided by National Institute of Standards and Technology. Note: Materials may be edited for content and length.


Cite This Page:

National Institute of Standards and Technology. "Scientists Use Electron Beam To Unravel The Secrets Of An 'Atomic Switch'." ScienceDaily. ScienceDaily, 18 August 2006. <www.sciencedaily.com/releases/2006/08/060818015934.htm>.
National Institute of Standards and Technology. (2006, August 18). Scientists Use Electron Beam To Unravel The Secrets Of An 'Atomic Switch'. ScienceDaily. Retrieved July 30, 2014 from www.sciencedaily.com/releases/2006/08/060818015934.htm
National Institute of Standards and Technology. "Scientists Use Electron Beam To Unravel The Secrets Of An 'Atomic Switch'." ScienceDaily. www.sciencedaily.com/releases/2006/08/060818015934.htm (accessed July 30, 2014).

Share This




More Matter & Energy News

Wednesday, July 30, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Climate Change Could Cost Billions, According To White House

Climate Change Could Cost Billions, According To White House

Newsy (July 29, 2014) A report from the White House warns not curbing greenhouse gas emissions could cost the U.S. billions. Video provided by Newsy
Powered by NewsLook.com
Stranded Whale Watching Boat Returns to Boston

Stranded Whale Watching Boat Returns to Boston

Reuters - US Online Video (July 29, 2014) Passengers stuck overnight on a whale watching boat return safely to Boston. Linda So reports. Video provided by Reuters
Powered by NewsLook.com
Baluchistan Mining Eyes an Uncertain Future

Baluchistan Mining Eyes an Uncertain Future

AFP (July 29, 2014) Coal mining is one of the major industries in Baluchistan but a lack of infrastructure and frequent accidents mean that the area has yet to hit its potential. Duration: 01:58 Video provided by AFP
Powered by NewsLook.com
Easier Nuclear Construction Promises Fall Short

Easier Nuclear Construction Promises Fall Short

AP (July 29, 2014) The U.S. nuclear industry started building its first new plants using prefabricated Lego-like blocks meant to save time and prevent the cost overruns that crippled the sector decades ago. So far, it's not working. (July 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:
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