News
Brookhaven National Laboratory Hits World High in Accurately Measuring Materials' Defects
| At Brookhaven National Laboratory
(BNL), the tiniest
defects in materials can now be measured with the highest accuracy ever
achieved — akin to finding a speck of dust in an area the size of the
United States. Researchers in the Energy Sciences & Technology
Department (ES&T) have developed a technique to measure defects with
picometer accuracy, a picometer being a trillionth of a meter.
The research was reported in the December 11 issue of the journal Physical
Review Letters. The paper’s authors are Lijun Wu and Yimei Zhu, both of
ES&T, and J. Tafto, visiting BNL scientist from the University of
Oslo, Norway. The work is also featured in Physical
Review Focus. Science News ran a feature on
the research in their December 2, 2000 issue, and Business News has it in
a January issue.
|
From left, Yimei Zhu, Lijun Wu, and
Douglas Gillette, all of the EST Dept. |
“Defects are tiny deviations from the normal positions of atoms in
materials, and they often control a material’s function,” Zhu said.
“For example, certain defects allow a larger current to be transported
without resistance in superconductors, or improve the electronic, magnetic
and optical properties of semiconductors used in computers or digital
equipment. This new technique enables researchers to measure defects with
unprecedented accuracy, which is important for designing advanced
materials.”
The researchers named the new technique interferometry in coherent
electron diffraction. The method, which requires the use of a
one-of-a-kind transmission electron microscope, is complementary to
neutron-scattering techniques and x-ray scattering techniques.
Because of its small probe size and high spatial resolution, electron
microscopy is particularly suited for the investigation of an extremely
tiny area of a material, making it indispensable for research in
nanometer-scale science and technology. In this new form of interferometry
developed at BNL, electrons from a coherent source of light hit a sample
from different directions and form particular "interference"
patterns, which can be viewed by a detector. This information is then
interpreted by scientists to measure defects in materials.
The BNL researchers’ expertise in materials science coupled with a
transmission electron microscope made the new technique possible. Built by
JEOL of Tokyo according to Brookhaven researchers’ specifications, the
microscope on which the research was performed can magnify samples up to
50 million times. At this magnification, an atom looks as big as a ping
pong ball, and a ping pong ball would look as big as the earth. One of the
best instruments of its kind in the world, the microscope is tailored for
research in solid-state physics, chemistry and biology, as well as
materials science.
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Building 475, Brookhaven National Laboratory, Upton, New York
11973-5000
Updated:
07/18/2005
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