Narrowest bridges Of Gold Are Also The Strongest, Study Finds

At an atomic scale, the tiniest bridge of gold -- that made of a single atom -- is actually the strongest, according to new research by engineers at the University at Buffalo's Laboratory for Quantum Devices. The counterintuitive finding is the result of experiments probing 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. An examination of these tiny, gold bridges revealed that they were stiffest when they comprised just a single atom.

The study was published in June in Physical Review B by a trio of UB researchers: postdoctoral fellow Jason Armstrong and professors Susan Hua and Harsh Deep Chopra, all in UB's Department of Mechanical and Aerospace Engineering. Support for the work came from National Science Foundation grants No. DMR-0706074 and No. DMR-0964830.

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 team said. "This study finds, however, that the ability of the material to resist elastic deformation actually increases with decreasing size."

Another observation the team made while studying the tiny gold necks: abrupt atomic displacements that occur as the gold tip and surface are drawn apart are not arbitrary, but follow well-defined rules of crystallography. More scientific highlights of the work are summarized in the Physical Review Focus of the American Physical Society at http://focus.aps.org/story/v27/st24.

UB's Laboratory for Quantum Devices, led by Chopra and Hua, works 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.