Scientists bend world's thinnest glass and see atoms dance

A research team led by David A. Muller, professor of applied and engineering physics and co-director of the Kavli Institute at Cornell for Nanoscale Science and Ute Kaiser from the University of Ulm, who both led the previous study on atomically thin glass, has used an electron microscope to bend, deform and melt the one molecule-thick glass. These are all things that happen just before glass shatters, and for the first time, the researchers have directly imaged such deformations and the resulting "dance" of rearranging atoms in silica glass, which forms the basis for everyday windowpanes. This newest work is published Oct. 11 in the journal Science.

Glass, what's known as an amorphous solid because its atoms are rigid like a crystal but disorderly like a liquid, is notoriously hard to study, said Pinshane Huang, a graduate student working with Muller and the paper's first author.

"Now, instead of just looking at its structure, we are looking at its dynamics and how it bends and breaks," Huang said. "This thinnest-ever glass gives us a new way of looking at glasses at the single-atom level, and how they break atom by atom." Added Muller: "No one has ever before been able to see the rearrangements of atoms in a glass when you push on it."

Sophisticated theories describe how these atoms behave when bent or broken, but only on the computer, said Jim Sethna, professor of physics and paper co-author. "Lots of people have made computer simulations, but this is the experimental realization of what the glass community has been looking for a long, long time."

With collaborators at both Cornell and Germany's University of Ulm, the researchers imaged the thin glass with two types of transmission electron microscopes. The electron beam heated up the glass, causing visible structural deformation at the interfaces between liquid and solid phases. Muller described the electrons as "tickling" the glass in order to deform it and simultaneously image what was happening.

To do their study, the researchers borrowed longstanding theories and predictions from scientists who study colloids -- suspensions of particles in liquid that are representative of atoms but can be observed directly because they are larger.

"A lot of what we did was to use their methods and tracking codes and ideas, and now that we can actually see atoms in a glass, we tried it with real atoms," Huang said.

The work was supported by the National Science Foundation, Cornell Center for Materials Research and Air Force Office of Science Research.