Finding a faulty atom

Researchers at Brookhaven National Laboratory have developed a technique to detect defects in materials with the highest accuracy ever achieved in such measurements.

The researchers managed to hone defect detection down a picometer, or one trillionth of a meter. Such pinpoint accuracy is said to be akin to finding a speck of dust in an area as big as the United States

‘Defects are tiny deviations from the normal positions of atoms in materials, and they often control a material’s function,’ said Yimei Zhu, a Brookhaven 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.

The researchers developed the new technique, which they named interferometry in coherent electron diffraction, using a unique transmission electron microscope.

Because of its small probe size and high spatial resolution, electron microscopy is said to be particularly suited for the investigation of a minuscule area of a material.

In this new form of interferometry, electrons from a coherent source of light hit a sample from different directions and form particular ‘interference patterns’ that can be viewed by a detector.

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 table tennis ball — and a table tennis ball would look as big as the earth.

Believed to be 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.