Invited Paper IPF+NC-MoA7
Atomic Motion Observed with sub-Angstrom Resolution in the Electron Microscope

Monday, October 20, 2008, 4:00 pm, Room 312

The recent successful introduction of aberration correction optics into the electron microscope has produced an instrument that can routinely image the positions of single atoms and structure of small groups of atoms. In fact, the signal from a single atom is strong enough to obtain good quality images in a few tens of milli-seconds, allowing the taking of sequences of images to follow atomic processes. In the microscope, atomic level objects are vigorously excited by the electron beam, and this energy deposition is observed to speed up normal processes – island coalescence, structural changes, and nucleation of growth -- so that they are observable in relatively short times. In many cases, imaging in bulk specimens shows similar atomic level behavior. Thus stress relaxation and atomic redistribution within bulk structures may be observable in the presence of the electron beam, and so may be quantified if the electron beam interaction can be well understood. The combination of Electron Energy Loss Spectroscopy with atomic resolution imaging promises to obtain local electronic structure within the bulk, but changes in the bulk structure caused by energy deposition will complicate interpretation. This presentation will discuss these observations and suggest what types of mechanisms may contribute to the observed behavior.