Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Researchers Holding Steady in an Atomic-Scale Tug-of-War

01.04.2010
How hard do you have to pull on a single atom of—let’s say—gold to detach it from the end of a chain of like atoms?*

It’s a measure of the astonishing progress in nanotechnology that questions that once would have interested only physicists or chemists are now being asked by engineers. To help with the answers, a research team at the National Institute of Standards and Technology (NIST) has built an ultra-stable instrument for tugging on chains of atoms, an instrument that can maneuver and hold the position of an atomic probe to within 5 picometers, or 0.000 000 000 5 centimeters.**

The basic experiment uses a NIST-designed instrument inspired by the scanning tunneling microscope (STM). The NIST instrument uses as a probe a fine, pure gold wire drawn out to a sharp tip. The probe is touched to a flat gold surface, causing the tip and surface atoms to bond, and gradually pulled away until a single-atom chain (see figure) is formed and then breaks. The trick is to do this with such exquisite positional control that you can tell when the last two atoms are about to separate, and hold everything steady; you can at that point measure the stiffness and electrical conductance of the single-atom chain, before breaking it to measure its strength.

The NIST team used a combination of clever design and obsessive attention to sources of error to achieve results that otherwise would require heroic efforts at vibration isolation, according to engineer Jon Pratt. A fiber-optic system mounted just next to the probe uses the same gold surface touched by the probe as one mirror in a classic optical interferometer capable of detecting changes in movement far smaller than the wavelength of light. The signal from the interferometer is used to control the gap between surface and probe. Simultaneously, a tiny electric current flowing between the surface and probe is measured to determine when the junction has narrowed to the last two atoms in contact. Because there are so few atoms involved, electronics can register, with single-atom sensitivity, the distinct jumps in conductivity as the junction between probe and surface narrows.

The new instrument can be paired with a parallel research effort at NIST to create an accurate atomic-scale force sensor—for example, a microscopic diving-board-like cantilever whose stiffness has been calibrated on NIST’s Electrostatic Force Balance. Physicist Douglas Smith says the combination should make possible the direct measurement of force between two gold atoms in a way traceable to national measurement standards. And because any two gold atoms are essentially identical, that would give other researchers a direct method of calibrating their equipment. “We’re after something that people that do this kind of measurement could use as a benchmark to calibrate their instruments without having to go to all the trouble we do, " Smith says. "What if the experiment you’re performing calibrates itself because the measurement you’re making has intrinsic values? You can make an electrical measurement that’s fairly easy and by observing conductance you can tell when you’ve gotten to this single-atom chain. Then you can make your mechanical measurements knowing what those forces should be and recalibrate your instrument accordingly.”

In addition to its application to nanoscale mechanics, say the NIST team, their system’s long-term stability at the picometer scale has promise for studying the movement of electrons in one-dimensional systems and single-molecule spectroscopy.

* The answer, calculated from atomic models, should be something under 2 nanonewtons, or less than 0.000 000 007 ounces of force.

** D.T. Smith, J.R. Pratt, F. Tavazza, L.E. Levine and A.M. Chaka. An ultra-stable platform for the study of single-atom chains. J. Appl. Phys., in press, March, 2010.

Michael Baum | Newswise Science News
Further information:
http://www.nist.gov

More articles from Physics and Astronomy:

nachricht Physicists Design Ultrafocused Pulses
27.07.2017 | Universität Innsbruck

nachricht CCNY physicists master unexplored electron property
26.07.2017 | City College of New York

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Physicists Design Ultrafocused Pulses

Physicists working with researcher Oriol Romero-Isart devised a new simple scheme to theoretically generate arbitrarily short and focused electromagnetic fields. This new tool could be used for precise sensing and in microscopy.

Microwaves, heat radiation, light and X-radiation are examples for electromagnetic waves. Many applications require to focus the electromagnetic fields to...

Im Focus: Carbon Nanotubes Turn Electrical Current into Light-emitting Quasi-particles

Strong light-matter coupling in these semiconducting tubes may hold the key to electrically pumped lasers

Light-matter quasi-particles can be generated electrically in semiconducting carbon nanotubes. Material scientists and physicists from Heidelberg University...

Im Focus: Flexible proximity sensor creates smart surfaces

Fraunhofer IPA has developed a proximity sensor made from silicone and carbon nanotubes (CNT) which detects objects and determines their position. The materials and printing process used mean that the sensor is extremely flexible, economical and can be used for large surfaces. Industry and research partners can use and further develop this innovation straight away.

At first glance, the proximity sensor appears to be nothing special: a thin, elastic layer of silicone onto which black square surfaces are printed, but these...

Im Focus: 3-D scanning with water

3-D shape acquisition using water displacement as the shape sensor for the reconstruction of complex objects

A global team of computer scientists and engineers have developed an innovative technique that more completely reconstructs challenging 3D objects. An ancient...

Im Focus: Manipulating Electron Spins Without Loss of Information

Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.

For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

Closing the Sustainability Circle: Protection of Food with Biobased Materials

21.07.2017 | Event News

»We are bringing Additive Manufacturing to SMEs«

19.07.2017 | Event News

 
Latest News

Programming cells with computer-like logic

27.07.2017 | Life Sciences

Identified the component that allows a lethal bacteria to spread resistance to antibiotics

27.07.2017 | Life Sciences

Malaria Already Endemic in the Mediterranean by the Roman Period

27.07.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>