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Lehigh to Acquire Electron Microscopy Instruments

Photonics.com
Dec 2003
BETHLEHEM, Pa., Dec. 12 -- Lehigh University said it will receive National Science Foundation funding to acquire a new, aberration-corrected transmission electron microscope and an aberration corrector for its existing scanning transmission electron microscope next spring. The new instruments will give scientists the long-sought-after ability to simultaneously locate and identify individual atoms in crystalline materials.

The aberration-corrected microscopes will permit the electron microscope to detect the presence of a single impurity in an atom. It will offer insights into the nature of a variety of phenomena, including the segregation of impurity atoms that control brittle fractures of steel in nuclear reactors, the chemistry of catalytic nanoparticles used to oxidate carbon monoxide and remove organic pollutants from groundwater and the microstructure of new ion-containing polymers that could provide protection against chemical warfare.

The microscopes achieve this improved resolution by correcting an imbalance in the lenses that focus the electron beam on the specimen being examined. The outer extremities of the lenses tend to focus more strongly than their centers, limiting the beam width to 1 or 2 nm, or about the width of five to six atoms. (One nanometer is equal to one one-billionth of a meter.)

An aberration corrector, aided by a sophisticated feedback mechanism, measures the amount of "over-focus" and adjusts the outermost of the lenses, known as the objective lens. The resulting beam measures 0.1 nm in width, or about half the width of an atom.

"This is like fitting a microscope with a new pair of reading glasses, giving it 20:20 vision," said Chris Kiely, professor of materials science and engineering and director of the Nanoscale Characterization Laboratory in the Center for Advanced Materials and Nanotechnology.

An improved understanding of the microscopic behaviors of atoms and molecules has led to advances in materials used in semiconductor chips, airplane wings, VCRs, cell phones and other modern devices. It has also given metallurgists new diagnostic capabilities. The Titanic, scientists now believe, may have been doomed while it was being built, when a handful of sulfur atoms slipped unseen into the grains of iron in the ship’s hull, rendering it brittle.

The new instruments will play a key role in the Lehigh Microscopy School, which attracts 150 to 200 participants from academia and industry to Lehigh every June.

For more information, visit: www.lehigh.edu



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