NEW IMAGING CAPABILITIES FOR MATERIALS ENABLED BY THE ELECTRON MICROSCOPE PIXEL ARRAY DETECTOR (EMPAD)

Abstract

Transmission electron microscopy is a ubiquitous tool for materials and biological characterization from the micron to atomic scales. While the most common use of transmission electron microscopy is to determine atomic-scale structures, from the protein signatures of Alzheimer’s disease to the arrangement of atoms within a transistor, the scattered electron beam encodes a wealth of information about the structure, chemistry, electrical, optical, and magnetic properties of matter. Conventional electron detectors, however, discard much of this information. A next frontier of atomic scale characterization of matter will be to detect, analyze, and utilize these new scattering signals. Here, a new generation of direct imaging detectors have already enabled pioneering work for cryo-electron microscopy to solve structures of biomolecules, giving us an atomic-scale view into the intricate workings of life and winning the Nobel Prize in Chemistry in 2017. To go beyond traditional electron microscopy techniques, new detectors must also be developed for diffraction imaging. During my PhD at Cornell, I developed and co-invented the Electron Microscope Pixel Array Detector (EMPAD), a fast, highly efficient “universal” detector for the electron microscope that is designed to re-capture and harness this missing information. The EMPAD is poised to have broad scientific and technological impact: we have licensed the EMPAD design to FEI, a subsidiary of Thermo Fisher Scientific. Moreover, in the two years since the first paper was published demonstrating the use of the EMPAD, initial studies applying the EMPAD to various materials and biological systems have demonstrated its broad, cross-disciplinary impact. In my dissertation, I will talk about: previous works on diffraction imaging and STEM diffraction detectors available in the field (Chapter 1), the capabilities of the EMPAD (Chapter 2), the EMPAD’s use for imaging magnetic fields and magnetic phases in FeGe thin films (Chapter 3), and new physics from ferroelectric polarization vortices (Chapter 4). In Chapter 5, I will discuss the future works that can be done with EMPAD. In fact, it is extremely encouraging to know that the imaging examples described in this thesis only represent a small fraction of the potential impact the EMPAD can achieve for the field of electron microscopy.