Quantum Necking in Stressed Metallic Nanowires
When a macroscopic metallic wire is subject to tensile stress, it necks down smoothly as it elongates. We show that metal wires with radii on the nanometer scale display remarkably different behavior. Taking surface self-diffusion of atoms as the dominant process, a PDE for nanowire shape evolution is derived from a semiclassical energy functional that includes electron-shell effects. A rich dynamics involving movement and interaction of surface kinks is found, and a new class of universal equilibrium shapes is predicted.
1. Evolution of an intially random nanowire into a universal
For comparison, see this atomic-resolution TEM video (16Mb mpeg) showing the fabrication of a gold nanowire, by the Takayanagi group .
2. Propagation of a Surface Intability
3. Necking of a nanowire under strain
For comparison, see this atomic-resolution TEM video (6.5Mb mpeg) of a strained gold nanowire, by the Takayanagi group .
Click here for a scientific article describing how these movies were made. Simulations by Dr. Jérôme Bürki .