With recent advances in detector technology and a new class of ptychographic phase-retrieval algorithms to unscramble multiple scattering, the resolution of the electron microscope is now limited only by the dose applied to the sample, and thermal vibrations of the atoms themselves. At high doses, these approaches have allowed us to image the detailed vibrational envelopes of individual atom columns as well as locating individual interstitial atoms. The three-dimensional nature of the reconstruction means atomic-scale interface roughness and step edges inside devices can be resolved – including modern gate-all-around transistors and Josephson junctions. Even the location of all atoms in thin amorphous films now seems within reach. The reduced sensitivity to chromatic aberrations also makes these approaches of interest for thick biological sections, polymer samples or operando liquid-cell experiments, where we have been able to demonstrate a fivefold improvement in dose efficiency over conventional cryo-EM.
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 Cornell Center for Materials Research and 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 his group holds the Guinness World Record for the highest resolution microscope.
He is a member of the National Academy of Engineering, 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, the Microscopy Society of America’s Burton Medal, the International Federation of Societies for Microscopy’s Cowley Medal, and the Ernst Ruska prize from the German Society for Electron Microscopy.