Mechanical and Civil Engineering Seminar

Mechanical and Civil Engineering Seminar Series

Title: A New Way to Image Atoms

Abstract: Electron microscopes use electrons with wavelengths of a few picometers and are potentially capable of imaging individual atoms in solids at a resolution ultimately set by the intrinsic size of an atom. Until very recently, the best resolution was more than an order magnitude worse than this. This was caused by two things – first the intrinsic aberrations in electron lenses are much worse than for optical lenses – it would be like trying to use a beer bottle as a magnifying glass. Second, electrons are multiply scattered inside the sample – a process described by Hans Bethe over 90 years ago. It's been a headache for electron microscopists ever since, but with our recent advances in detector technology and ptychographic reconstruction algorithms, the resolution of the electron microscope is now limited only by the dose to the sample, and thermal vibrations of the atoms themselves [1]. These approaches have also allowed us to image the internal structures of both magnetic and ferroelectric vortices, skyrmions and merons, including their singular points that are critical for accurately describing the topological properties of these field textures. The reduced sensitivity to chromatic aberrations also makes these ptychographic approaches of interest for thick biological samples such as 3D reconstructions of whole cells.

[1] Z. Chen, Y. Jiang, Y.-T. Shao, M. E. Holtz, M. Odstrčil, M. Guizar-Sicairos, I. Hanke, S. Ganschow, D. G. Schlom, and D. A. Muller. "Electron Ptychography Achieves Atomic-Resolution Limits Set by Lattice Vibrations" Science 372, (2021): 826–831

Bio: David Muller is the Samuel B. Eckert Professor of Engineering in the School of Applied and Engineering Physics at Cornell University, and co-director of the Kavli Institute for Nanoscale Science at Cornell. Muller received his BSc degree from the University of Sydney, his PhD degree in physics from Cornell, and was a research scientist at Bell Labs from 1997-2003. His research interests include new electron microscopy methods for the atomic-scale control and characterization of matter, including renewable energy applications. His group's inventions and advances in new microscopy technology have led to three Guinness World Records including for the highest resolution microscope.

He is a fellow of the American Physical Society, the Microscopy Society of America and the American Association for the Advancement of Science, and recipient of the APS Keithley Award For Advances in Measurement Science, the Microscopy Society of America Burton Medal, the International Federation of Societies for Microscopy Cowley Medal, and the Ernst Ruska prize from the German Society for Electron Microscopy.

NOTE: At this time, in-person Mechanical and Civil Engineering Lectures are open to all Caltech students/staff/faculty/visitors.