Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New Technique Reveals Structure of Films With High Resolution

30.10.2002


Scientists have developed and tested a new imaging technique that reveals the atomic structure of thin films with unprecedented resolution. For the first time, the technique has shown very precisely how the atoms of the first layers of a film rearrange under the action of the substrate on which the film is grown. The results of the study are reported as the cover story of the October issue of Nature Materials.



Above: Electron density map of one of the layers of the gadolinium oxide film close to the gallium arsenide substrate (top) and a layer in the substrate (bottom), by using the COBRA imaging technique. A comparison of both maps shows that the gadolinium atoms (around the yellow-red peaks) rearrange so that the maps mimic each other



“This technique directly provides a very precise image of atomic positions within a film and at the interface between a film and a substrate,” says Ron Pindak, a physicist at the National Synchrotron Light Source (NSLS) at the U.S. Department of Energy’s Brookhaven National Laboratory and one of the authors of the study. “With the current growing interest in the study of nanomaterials, which are the size of a few atoms, this technique will probably be key in devising such materials and understanding their properties.”

Thin films are currently used in many technologies, including electronic chips, coatings, and magnetic recording heads. To improve the properties of these materials and create even thinner structures – such as smaller electronic chips – scientists are now trying to understand how the films interact with the substrate on which they are grown.


“When you build a film on a substrate, the positions of the atoms of the film are slightly shifted, and some of these shifts can be very small,” says Roy Clarke, a physicist at the University of Michigan in Ann Arbor and another author of the study. “So it is important to be able to explain how these films behave at the atomic level.”

By building upon traditional x-ray diffraction, the newly devised technique provides such information. In this technique, x-rays are projected onto the film and the substrate pattern, which is then used to determine the positions of the atoms inside the film. The diffraction pattern of thin films is composed of ridge-like features called “Bragg rods,” hence the name of the technique: coherent Bragg rod analysis (COBRA).

The COBRA technique determines two key properties of the diffracted x-ray waves: their intensity and their phase, which describes the shift in position between the incident and diffracted x-ray waves. Though the amplitude is easily determined from the diffraction pattern, the phase is usually more difficult to determine, which is just what COBRA does.

“Key to the COBRA technique is a new approach to determining the phase of the diffracted x-ray waves,” says Yizhak Yacoby, physicist at the Hebrew University in Jerusalem and lead author of the study. “Unlike traditional x-ray diffraction techniques, COBRA does not rely on a priori guesses about the structure of the film and the substrate, and we do not need to prepare the sample in a special way – as with a transmission electron microscope.”

Yacoby, who started developing the technique four years ago, first applied it to known structures by using x-rays produced at the NSLS at Brookhaven, which allowed him to refine the technique. In their recent study, Yacoby and his collaborators applied the technique to a film made of gadolinium oxide grown on a gallium arsenide substrate using brighter x-rays at the Advanced Photon Source (APS) at Argonne National Laboratory in Illinois. Key to the successful data collection were two APS beam lines that Clarke and Edward Stern, a physicist at the University of Washington in Seattle, perfected for the past five years.

The researchers made unexpected observations. They noticed that two thirds of the gadolinium atoms in the first few layers of the film adjust to match the positions of the atoms in the substrate. The researchers also discovered that the structure of the first layers of the film mimics very closely the substrate’s structure, while the atoms in the layers farther away from the substrate are arranged more like those in the bulk form of gadolinium oxide. The layer stacking of the film also appeared to mimic very closely the substrate’s structure.

The scientists now intend to investigate the properties of various other films. Yacoby, who has already submitted patents for the COBRA technique, is confident that it will have many applications in the design of electronic devices based on thin films, the self-assembly of layers made of metal oxides used in catalysis, and the study of films made of large organic molecules, such as proteins.

This work was funded by the U.S. Department of Energy, which supports basic research in a variety of scientific fields.

For more information, contact:
Karen McNulty Walsh, 631 344-8350, or
Mona S. Rowe, 631 344-5056
Writer: Patrice Pages

Karen McNulty Walsh | EurekAlert!
Further information:
http://www.bnl.gov/
http://www.bnl.gov/bnlweb/pubaf/pr/2002/bnlpr102902.htm

More articles from Process Engineering:

nachricht Fraunhofer researchers develop measuring system for ZF factory in Saarbrücken
21.11.2017 | Fraunhofer-Institut für Zerstörungsfreie Prüfverfahren IZFP

nachricht New manufacturing process for SiC power devices opens market to more competition
14.09.2017 | North Carolina State University

All articles from Process Engineering >>>

The most recent press releases about innovation >>>

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

Im Focus: Nanoparticles help with malaria diagnosis – new rapid test in development

The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.

Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

Corporate coworking as a driver of innovation

22.11.2017 | Business and Finance

PPPL scientists deliver new high-resolution diagnostic to national laser facility

22.11.2017 | Physics and Astronomy

Quantum optics allows us to abandon expensive lasers in spectroscopy

22.11.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>