Harnessing Nanosecond STEM Electron Pulses with an Electrostatic Beam Blanker for Angstrom Spatial Resolution in Time-Resolved Studies of Electrically Excited Dynamics

In the realm of dynamic imaging and analysis of electronically driven phenomena, the utilization of nanosecond scanning transmission electron microscope (STEM) electron pulses generated from an electrostatic beam blanker (ESBB) presents a novel frontier.While other methods of generating short electron pulses in STEM have been demonstrated, they generally struggle to preserve electron probe coherence.[1-3] Here, we present a pioneering approach leveraging a probe corrected STEM platform (TFS Spectra 300) and an ESBB to generate electron pulses, enabling the investigation of material dynamics under electrical excitation with angstrom level spatial resolution.Our technique also enables 5D-STEM (time-resolved Four-Dimensional STEM), pushing the boundaries of spatiotemporal resolution in the study of electrically induced phase transformations, carrier dynamics, and thermal diffusion in various materials.By employing an ESBB, we can achieve precise control over electron pulse duration and timing, with variable operational range from steady state down to 3.5ns pulses and 1MHz to single shot repetition rate.In Figure 1, we demonstrate the 5DSTEM capability by mapping the rise of an electric field across gap between two electrodes resulting from a voltage pulse delivered to a Hummingbird electrochemical holder.Using a pump-probe technique, we are able to measure the direct-beam deflection in 4DSTEM as a function of delay time between the arrival of the voltage pulses and the ns electron pulses.This experiment allows for benchmarking of the ESBB pulse duration as well as being a reliable measurement of time-zero.While similar work has been demonstrated using photoexcited electrons, this tool allows for the spatial resolution resulting from the 4DSTEM capabilities and improved beam coherence.[4] The presented new method preserves sub-nanometer spatial resolution for STEM imaging and 300meV energy resolution for STEM-EELS, ensuring detailed characterization of material structures even during rapid temporal evolution.Figure 2 shows the ability to easily image an evaporated gold standard at atomic resolution with the ESBB operating at 50ns and 1MHz.Here, we will discuss the experimental setup, highlighting the integration of the ESBB into the microscopy platform along with our ability to deliver up to 50V pulses in situ with rise times of 2ns.We will showcase the application of our technique in elucidating dynamic phenomena, emphasizing its potential in advancing fields such as quantum information science and device engineering.This combination of high temporal and spatial resolution will be instrumental in unraveling complex dynamics at the atomic level, shedding light on elusive transient states and mechanisms governing electronic excitations [5].