Revealing the Dynamics of Reactive Materials with Ultrafast Transmission Electron Microscopy

Recent developments in instrumentation have made it a very exciting time to perform both fundamental and applied research in the electron microscope. The development of nanosecond and faster photoemission electron sources offers the chance to move the high spatial resolution world of electron microscopy into the ultrafast world of materials dynamics. Reactive materials are known to release large amount of heat via rapid exothermic chemical reactions upon receiving an initiating energy input. Due to relatively fast propagating reaction fronts, Ultrafast Transmission Electron Microscopy (UTEM) has immense potential in discovering the fundamental processes leading to reaction initiation and evolution in reactive materials. In the UTEM, while samples are excited with a nanosecond pulsed laser to trigger reactions via photothermal processes, a second pulse with a known time delay is used to stimulate the photoemission of electrons from the cathode. This single-shot approach makes it possible to capture various stages of irreversible processes with high temporal resolution and understand how a dynamic process evolves in reactive materials. In this presentation, examples of single-shot UTEM studies of reactive materials will be presented. Short-lived transient processes involved in reactions and the evolution dynamics will be discussed to obtain new insights into the reaction processes.