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Posted: Apr 03, 2006
New record set for smallest X-ray nano-spot
(Nanowerk News) An award-winning device developed at the
U.S. Department of Energy's Argonne National Laboratory has set a world's
record for tiny spot size with a hard X-ray beam.
The device is called a Multilayer Laue Lens. The wafer from which the device
was made won a 2005 R&D
100 award, given to the world's top 100 scientific
and technological innovations. The enhancements to the device have now increased
its ability to focus the X-rays with an energy level of 19.5 keV to 30 nanometers.
For comparison, the period at the end of this sentence is approximately one
million nanometers in diameter.
The lens – just like the lens of a camera – allows precise focusing of the
X-ray light.Using the lens, researchers will be able to visualize three-dimensional
electronic circuit boards to find circuit errors, or map impurities in biological
or environmental samples at the nanometer scale. They can also analyze samples
inside high-pressure or high-temperature cells, since hard X-rays, unlike soft
X-rays, are able to penetrate container walls.
Other examples of uses of the new lens include development of smaller, better-performing
and more reliable computers and telecommunications equipment; improving materials
for energy efficient lighting, motors, fuel cells and solar energy production;
production of lighter, sturdier, safer transportation vehicles through advanced
materials with tailored properties; imaging cell division and tumor growth,
providing a new mechanism for the early detection of cancer; and faster, more
sensitive detection of hazards in local and global environments.
The researchers developed the record-setting lens by depositing 728 layers
of material, one layer at a time, on a silicon substrate wafer. The thickness
of the layer stack, when completed, was 12.4 microns. The wafer is then sectioned
into bars that are used to make the lenses for the X-ray.
"The accomplishment here is two-fold," said lead author Hyon Chol Kang. "The
first is to grow that many layers without peeling, and, second, to cut and
polish a bar without damaging the lens. We're continuing the development, and
calculations for an idealized structure indicate that a focus of one nanometer
is not prohibited by any known physics. The great challenge will be to grow
the idealized structure."
The optical design is akin to a linear Fresnel lens conventionally made by
photolithography, but with the crucial difference that the diffraction structure
is formed from many individually sputtered layers. High quality sputtered layers
can be grown with thicknesses of 1 nm, and it is this control which makes the
multilayer lens possible.
The new device is being used at the Advanced
Photon Source at Argonne, which
produces the most brilliant X-rays in the Western Hemisphere. It will also
be particularly useful as the Center for Nanoscale
Materials at Argonne becomes
operational later this year.
Researchers Al Macrander, Chian Liu and Raymond Conley, all part of the Advanced
Photon Source Experimental Facilities
Division optics fabrication and metrology group, developed the lens wafers
which won the 2005 R&D 100 award. They are joined by Stefan Vogt, also
of the Experimental Facilities Division; Kang and Brian Stephenson of the Materials
Science Division at Argonne, and Jorg Maser of the Accelerator
Systems Division at Argonne. The work is especially meaningful for Maser, who predicted the
theoretical ability of an X-ray lens to focus at this small size in his doctoral
dissertation in 1994.
The nation's first national laboratory, Argonne National Laboratory conducts
basic and applied scientific research across a wide spectrum of disciplines,
ranging from high-energy physics to climatology and biotechnology. Since 1990,
Argonne has worked with more than 600 companies and numerous federal agencies
and other organizations to help advance America's scientific leadership and
prepare the nation for the future. Argonne is managed by the University
of Chicago for the U.S.
Department of Energy's Office