Ultrafast Transmission Electron Microscopy and Electron Diffraction

Abstract

The development and application of pump-probe instrumentation to study rather complex transient events in the solid state, soft matter and life sciences domains has been an area of enormous interest recently. For many years the emphasis has been on the laser-pump and laser-probe approach, followed by the laser-pump and x-ray probe approach. Lately, another method, the laser-pump electron-probe technique, has been gaining interest. Very early experiments using this technique have used electrons to explore gas-phase diffraction of photo-stimulated chemical reactions, followed by experiments in the solid state domain, studying for example, rapid phase transformations, solidification processes, twinning, and shock propagation. The following chapter will focus on the emerging area of ultrafast transmission electron microscopy, or simply ultrafast electron microscopy (UEM), as well as on ultrafast electron diffraction (UED). The topics included are electron sources for pulsed operation and the appropriate emitter materials for this application, electron pulse propagation, electron- and laser-material interactions, the operational challenges during an UEM or UED experiment, i.e., time-resolution and synchronization, the experimental variations, and the challenges encountered when attempting to detect ultrafast experimental processes.