New technique shows unprecedented accuracy in measuring materials defects

Upton, New York–Nov. 21, 2000–Researchers at the U.S. Department of Energy’s Brookhaven National Laboratory (BNL) have developed a technique to detect defects in materials with picometer (one trillionth of a meter) accuracy. This is the highest accuracy ever achieved in such measurements, akin to finding a speck of dust in an area as large as the U.S.

“Defects are tiny deviations from the normal positions of atoms in materials, and they often control a material’s function,” explains Yimei Zhu, BNL materials physicist and lead researcher on the project. “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 developed the technique, interferometry in coherent electron diffraction, using a one-of-a-kind transmission electron telescope. The technique is complementary to neutron-scattering techniques that require reactors or accelerators, and x-ray-scattering techniques that require a synchrotron. Due to its small probe size and high spatial resolution, electron microscopy is particularly well suited for the investigation of an extremely small area of a material, the researchers report, making it indispensable for research in nanometer-scale science and technology. In this new form of interferometry, electrons from a coherent source of light hit a sample from different directions and form particular “interface” patterns, which can be viewed by a detector. This information is then taken and interpreted by scientists to measure defects in materials.


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