UC Berkeley

Ultrafast electron diffraction is a developing technique for recording the evolution of atomic structure during dynamic processes. While many exciting discoveries and important observations have been made so far, the technique still faces instrumentation, modeling, and other challenges that inhibit materials science studies, especially of quantum and nanoscale materials. In this dissertation, I describe several developments of UED technology and modeling capabilities to overcome these challenges as well as show a couple of scientific applications. I begin with a general introduction to UED and its value to materials science. I then describe the scattering theory underlying UED patterns and demonstrate a multislice approach that dramatically improves quantitative retrieval of atomic motions in crystals. After this, I introduce the High Repetition-rate Electron Scattering (HiRES) beamline, a state-of-the-art high-brightness UED setup which enables several advances in UED capabilities. I follow up by detailing the first scientific study using the beamline, where a unique light-induced structural melt-recovery process in a quantum material was recorded for the first time. I then show proof-of-principle demonstrations of nanoscale probing enabled by HiRES, including diffraction from isolated nanomaterials as well as focused nanoprobes for nanodiffraction and nanoimaging. Following this, I describe progress towards plasmon-enhanced nanoemitters and how they can be used to further improve the brightness of UED nanoprobes. Finally, I briefly tie together these varied developments and outline areas for further development and scientific exploration. Altogether, the work detailed here expands the reach of UED for study of quantum and nanoscale materials and lays groundwork for further advances that will enable new, wide-open frontiers in materials science.