Tiniest gold has strength of Goliath

U. BUFFALO (US) — At an atomic scale, the narrowest bridge of gold, made of a single atom, is paradoxically the strongest, according to new research.

Postdoctoral fellow Jason Armstrong and Susan Hua and Harsh Deep Chopra, professors of mechanical and aerospace engineering at the University at Buffalo, probed the characteristics of atomic-scale necks of gold that formed when the pointed, gold tip of a cantilever was pushed into a flat, gold surface.


The tiny, gold bridges proved to be stiffest when they comprised just a single atom.

As engineers look to build devices such as computer circuits with ever-smaller parts, it is critical to learn more about how tiny components comprising a single atom or a few atoms might behave. The physical properties of atomic-scale gadgets differ from those of larger, “bulk” counterparts.

“Everyday intuition would suggest that devices made of just a few atoms would be highly susceptible to mechanical forces,” the scientists write in the study, published in Physical Review B. “However, the ability of the material to resist elastic deformation actually increases with decreasing size.”

The researchers also observed that abrupt atomic displacements that occur as the gold tip and surface are drawn apart are not arbitrary, but follow well-defined rules of crystallography.

Chopra and Hua, work on mapping the evolution of various physical properties of materials—including mechanical, magnetic, and magneto-transport behavior—as sample sizes grow from a single atom to bulk, a task that requires technology capable of capturing a single or few atoms between probes, and further pushing and pulling on the atoms to study their response.

The technology was recently licensed to Precision Scientific Instruments, a western New York start-up company.

“The instruments and methods are incredibly precise and capable of deforming the sample at the picometer scale (about 100 times smaller than an atom), which means literally stretching the bond lengths, and simultaneously measuring the forces at the piconewton level, as well as various other properties,” says Gerry Murak, president and cofounder.

“As a very broad perspective, by enabling researchers to probe the very small, the technology could speed advances in fields ranging from satellite communications to health care.

“Small is exciting, and atomic scale devices are the new frontier of technology. Metrology systems capable of probing the behavior of atomic-scale devices are sorely needed, and this technology gives us a unique platform.”

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