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Abstract
In recent years, there is a strong interest in ptychography, which computationally constructions a model of the sample from series of diffraction data collected from electron microscopes [1]. We have demonstrated a resolution of 0.67 Å or better using ptychography with a 20 keV electron beam operating in a transmission mode using a SEM with a cold emission gun and immersion lens.
We achieved this through combination of: adding a simple diffraction projector lens to our SEM; using an un-coated hybrid direct electron detector [3]; and incorporating correction of diffraction
projector distortions within a multi-slice ptychographic reconstruction process. Measurement and corrections of lens distortions is in general not trivial, so in our work we have simplified distortion evaluation using machine learning methods, as will be described. Also, using low energy scanning transmission electron diffraction in a SEM has provided us very valuable information for understanding the structure of novel polymer structures, as will be illustrated. These advances serve to widen access to, and hence help democratize, information that is currently only available from high-end TEM. At low bean energies interesting possibilities are presented with computationally assisted SEM, particularly with imaging thin, low atomic-number based samples, which present greater information at lower energies. This may in the longer-term assist in the structural determination of proteins with masses below about 100 kDa.
Speaker Bio
Arthur Blackburn is the Hitachi High-Tech Canada Research Chair, Co-Director of the Advanced Microscopy Facility and Assistant Professor in the Department of Physics and Astronomy at the
University of Victoria. Prior to joining the University of Victoria, he was a Senior Research Scientist in the Hitachi Cambridge Laboratory, embedded with the Cavendish Laboratory of the University of Cambridge. He progressed to this role after completing his PhD within the University of Cambridge, Department of Physics.