Featured Research

from universities, journals, and other organizations

New twist on the electron beam

Date:
February 5, 2011
Source:
National Institute of Standards and Technology (NIST)
Summary:
Researchers have found a novel, and potentially widely applicable, method to expand the capabilities of conventional transmission electron microscopes by adding a new twist to their electron beams.

NIST researchers twisted the flat electron wavefronts into a fan of helices using a very thin film with a 5-micron-diameter pattern of nanoscale slits, which combines the wavefronts to create spiral forms similar to a pasta maker extruding rotini. This method produces several electron beams fanning out in different directions, with each beam made of electrons that orbit around the direction of the beam.
Credit: B. McMorran/NIST

Electron microscopes are among the most widely used scientific and medical tools for studying and understanding a wide range of materials, from biological tissue to miniature magnetic devices, at tiny levels of detail. Now, researchers at the National Institute of Standards and Technology (NIST) have found a novel and potentially widely applicable method to expand the capabilities of conventional transmission electron microscopes (TEMs). Passing electrons through a nanometer-scale grating, the scientists imparted the resulting electron waves with so much orbital momentum that they maintained a corkscrew shape in free space.

The development opens the possibility of adapting transmission electron microscopy, which can see tinier details than optical microscopy and can study a wider range of materials than scanning probe microscopy, for quick and inexpensive imaging of a larger set of magnetic and biological materials with atomic-scale resolution.

"The spiral shape and angular momentum of these electrons will let us look at a greater variety of materials in ways that were previously inaccessible to TEM users," said Ben McMorran, one of the authors of the forthcoming research paper. "Outfitting a TEM with a nanograting like we used in our experiment could be a low-cost way to dramatically expand the microscope's capabilities."

Although NIST researchers were not the first to manipulate a beam of electrons in this way, their device was much smaller, separated the fanned out beams 10 times more widely than previous experiments, and spun up the electrons with 100 times the orbital momentum. This increase in orbital momentum enabled them to determine that the electron corkscrew, while remarkably stable, gradually spreads out over time. The group's work will be reported in the Jan. 14, 2011, issue of the journal Science.

Electrons in electron beams behave like rippling waves that move through space like a wave of light, McMorran said. Unlike wavefronts of light, which are hundreds of nanometers apart (a distance called the wavelength), the wavelengths of electrons are measured in picometers (trillionths of a meter), which make them excellent for imaging tiny objects such as atoms because of their comparable dimensions. In an ordinary electron beam, the electron wavefronts are relatively flat and uniform.

To spin up the electrons and give them orbital momentum, the NIST researchers twisted the flat electron wavefronts into a fan of helices using a very thin film with a 5-micron-diameter pattern of nanoscale slits. The pattern affects the shape of the electron wavefronts passing through it, amplifying some of the wave peaks and eliminating some of the wave valleys, to create a spiral form similar to a pasta maker extruding rotini. This method produces several electron beams fanning out in different directions, with each beam made of electrons that orbit around the direction of the beam.

The researchers knew they were successful because when they detected the electrons -- which were recorded as millions of individual particles building up an image -- they had formed donut-like or spiral patterns, indicating a helical shape.

Transmission electron microscopy creates images by shooting trillions of electrons through an object and measuring their absorption, deflection and energy loss. TEMs equipped with corkscrew electron beams could also monitor how the particles exert torque on a material and how a material affects the spiral shape of transmitted electrons, helping scientists build a more complete picture of the material's structure.

For example, these special electron beams have the potential to help obtain more information from magnetic materials.

"Magnetism, at its most fundamental, results from charges spinning and orbiting," McMorran said. "So an electron beam that itself carries angular momentum makes a good tool for probing magnetic materials."

A beam of corkscrew-shaped electrons, when interacting with a specimen, can exert torque on the material, by exchanging angular momentum with its atoms. In this way, the corkscrew electrons could obtain more information in the process than beams with ordinary electrons, which do not carry this orbital angular momentum.

This technique could also help improve TEM images of transparent objects like biological specimens. Biological material can be difficult to image in ordinary TEMs because electrons pass through it without deflecting. But by using corkscrew electron beams, researchers hope to provide high-contrast, high-resolution images of biological samples by looking at how the spiral wavefronts get distorted as they pass through such transparent objects.

While these imaging applications have not yet been demonstrated, producing corkscrew electrons with nanogratings in a TEM provides a significant step toward expanding the capabilities of existing microscopes.


Story Source:

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


Journal Reference:

  1. B. J. McMorran, A. Agrawal, I. M. Anderson, A. A. Herzing, H. J. Lezec, J. J. McClelland, J. Unguris. Electron Vortex Beams with High Quanta of Orbital Angular Momentum. Science, 2011; 331 (6014): 192 DOI: 10.1126/science.1198804

Cite This Page:

National Institute of Standards and Technology (NIST). "New twist on the electron beam." ScienceDaily. ScienceDaily, 5 February 2011. <www.sciencedaily.com/releases/2011/01/110120111330.htm>.
National Institute of Standards and Technology (NIST). (2011, February 5). New twist on the electron beam. ScienceDaily. Retrieved April 24, 2014 from www.sciencedaily.com/releases/2011/01/110120111330.htm
National Institute of Standards and Technology (NIST). "New twist on the electron beam." ScienceDaily. www.sciencedaily.com/releases/2011/01/110120111330.htm (accessed April 24, 2014).

Share This



More Matter & Energy News

Thursday, April 24, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Next Stop America for France's TGV?

Next Stop America for France's TGV?

Reuters - Business Video Online (Apr. 24, 2014) General Electric keeps quiet on reports it's in talks to buy French turbine and train maker Alstom. Ivor Bennett reports on what could be an embarrassing rumour for the French government, with business-friendly reforms proving a hard sell. Video provided by Reuters
Powered by NewsLook.com
Raw: Obama Plays Soccer With Japanese Robot

Raw: Obama Plays Soccer With Japanese Robot

AP (Apr. 24, 2014) President Obama briefly played soccer with a robot during his visit to Japan on Thursday. The President has been emphasizing technology along with security concerns during his visit. (April 24) Video provided by AP
Powered by NewsLook.com
Obama Encourages Japanese Student-Scientists

Obama Encourages Japanese Student-Scientists

AP (Apr. 24, 2014) President Obama spoke with student innovators in Japan and urged them to take part in increased opportunities for student exchanges with the US. (April 24) Video provided by AP
Powered by NewsLook.com
UN Joint Mission Starts Removing Landmines in Cyprus

UN Joint Mission Starts Removing Landmines in Cyprus

AFP (Apr. 23, 2014) The UN mission in Cyprus (UNFICYP) led a mine clearance demonstration on Wednesday in the UN-controlled buffer zone where demining operations are being conducted near the Cypriot village of Mammari. Duration: 01:00 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