Abstract: The advent of electron microscopy has revolutionized materials discovery. However, one of the main barriers is the cost of expensive aberration correcting lenses for atom-by-atom imaging. To address this challenge, I will show how electron ptychography, an iterative computation imaging technique, can provide resolution in conventional, non-aberration corrected microscopes beyond aberration-correcting instrumentation, providing state-of-the-art materials characterization to many institutions that lack the funds or facilities to house such expensive, sensitive equipment. This work is enabled by the recent development of high-dynamic range, high-speed direct electron detectors such as the electron microscope pixel array detector (EMPAD). Beyond structural imaging, new direct electron detectors can provide novel ways to investigate the natural order parameters of emergent materials. One example is the presence of an electric toroidal moment in a ferro-rotational phase. Here, I will describe techniques in which we can 1) measure the change orbital angular momentum of the electron beam as it interacts with this ferro-rotational phase and 2) uncover its local chiral order in three-dimensions. These methods present new ways in which new high-dynamic range electron detectors can aid the investigation of emergent topological structures, crucial for the development of ferroelectric non-volatile memory.

Speaker Lab Website: https://kxnlab.uoregon.edu/