The Many Facets of Ultrafast Electron Diffraction and Microscopy: Development and Applications

Abstract

In the past two decades, the rapid pace in the development of table-top ultrafast electron diffraction and microscopy instrumentation has ushered in a new area of investigating structural dynamics and related material property responses. In this chapter, we will review the multifaceted development involving gas-phase ultrafast electron diffraction for investigating photochemistry (gas phase UED), surface-sensitive ultrafast electron nanocrystallography (UEnC) and ultrafast photovoltamnetry (UPV) for probing subsurfaces, surfaces, and supported nanoparticles, as well as ultrafast electron crystallography (UEC) for the studies of molecular crystals and quantum materials. Prototypical examples of data collections, core technologies, and specialized protocols for structure analysis are presented in some detail with the hope that they can be reproduced by interested readers in their own studies. The need to simultaneously obtain information about the electronic states, functionalities, as well as structure dynamics motivates the development of ultrafast electron microscopy (UEM) in which diffraction, imaging, and spectroscopy are united to enable multimodality observations on ultrafast timescales for a broad range of materials science problems. The second part of the chapter covers the latest UEM technologies supported by new developments in generating high-brightness electron bunches, and the RF-based techniques for phase-space manipulations. Based on current progress, frank assessments about the performance in different areas and limitations are provided.