Goeppert Award: Democratizing Electron Microscopy with Computational Lenses

Electrons are fundamental particles that can used as imaging probes to uncover worlds beyond the resolution of light.  However, electron microscopes utilize electromagnetic lenses that have intrinsic spherical aberrations, making them difficult to focus.  In the early 2000s, aberration correctors were developed for scanning transmission electron microscopes (STEMs) that correct for these aberrations and could focus the electron beam down to sub-Angstrom resolution, allowing scientists to push imaging resolution and develop chemical maps at the atomic level.   However, aberration correctors tend to be expensive and their facilities are costly to run.  During my PhD, I worked on a new type of direct electron camera called the electron microscope pixel array detector (EMPAD) that captures information at high-speed and high-dynamic range, beyond the limits of CMOS and CCD detectors.   With the EMPAD, I can apply electron ptychography, a phase retrieval technique that reconstructs the full electron wave function while providing higher resolution images than aberration-corrected STEMs.  Electron ptychography as a computational lens approach can democratize science; here, institutions are no longer dependent on expensive aberration-corrected STEMs to achieve sub-Angstrom resolution and can bypass restrictions from thermal, vibrational and external field effects placed by these systems. In addition, I can also reconstruct the electric or magnetic field at high precision simply by measuring their effects from the diffraction pattern. My research goal is to extend electron microscopy while striving for its democratization.  In my talk, I will discuss how my group can visualize the 3D formation of magnetic skyrmions using Lorentz mutlislice electron ptychography.  Furthermore, my research group can provide the 3D reconstruction of Er:CeO₂ heterostructures with different zone-axes at sub-Angstrom resolution, a potential candidate for quantum memory because of its telecom wavelength. Finally, I will discuss challenges and efforts in group to not only push for higher spatial, but also time resolution.