Speaker
Description
Recent advances in ultrafast electron microscopy have highlighted the importance of understanding the generation, control, and characterization of pulsed electron beams for studying electron-light-matter interactions at the nanoscale. Here, we present the development and characterization of an ultrafast scanning electron microscope (USEM) based on a laser-driven Schottky field-emission source, where femtosecond UV laser pulses generated from the third harmonic of a Ti:sapphire laser induce linear photoemission from the Schottky tip. Using a combination of STEM imaging and a Timepix3 detector, we investigate the influence of extractor voltage, condenser lens settings, source tilt, source shift, and laser power on the density and spatial profile of the generated electron beam. The measurements reveal the critical role of electron-optical alignment and voltage conditions in the electron column in determining beam shape, stability, and emission efficiency. Furthermore, the incorporation of a time-delayed laser pulse onto the sample enables pump-probe measurements through the generation of optical near-fields, while the resulting electron-matter interactions are analyzed using fiber-based cathodoluminescence and Timepix3 detectors. These results provide a route for developing and optimizing laser-driven electron sources in USEM and establish a foundation for future investigations of ultrafast electron-light-matter interactions, near-field-driven dynamics, and time-resolved spectroscopy in SEM-based measurements.