Ultrafast Transmission Electron Microscopy: Instrumental Developments and the Probing of Nonlinear Structural Dynamics
Alexander Schröder a, Andreas Wendeln a, Jonathan Weber a, Kai Nettersheim a, Rieke von Seggern a, Soufiane El-Kabil a, Sascha Schäfer a b
a Department of Physics, University of Regensburg, Regensburg, Germany
b Regensburg Center for Ultrafast Nanoscopy, University of Regensburg, Regensburg, Germany
Proceedings of MATSUS Fall 2025 Conference (MATSUSFall25)
E.23 Materials in motion: Imaging nanoscale dynamics with photons and electrons - #NanoDyn
València, Spain, 2025 October 20th - 24th
Organizer: Seryio Saris
Invited Speaker, Sascha Schäfer, presentation 306
Publication date: 17th July 2025

Time-resolved variants of transmission electron microscopy have started to provide an unparalleled view into the fast and ultrafast dynamics of solid-state nanostructures. A crucial instrumental pre-requisite for constructing the next generation of time-resolved electron microscopes is the development of novel pulsed electron sources, fast detectors and versatile sample excitation schemes. In the first part of the talk, our recent development of a novel laser-driven cold-field emitter source is described [1]. The properties of extracted photoelectron pulses, including the achieved electron pulse duration, spectral width, and electron beam brightness, are characterized in detail, and the advantages of aberration-corretected ultrafast transmission electron microscopy are discussed. 

The second part focusses on the application of event-based TimePix3 electron detectors for the time-resolved probing of nonlinear structural dynamics in nanoscale resonatorss. We demonstrate the phase-resolved mapping of nonlinear Duffing modes in a silicon membrane resonator with quality factors exceeding 105. Higher harmonics of the driving frequency are observed in the structural response, indicatig the emergencs of multi-mode coupling channels with large effective nonlinearities. At the largest driving strengths, periode doubling bifurcations emerge highlighting the onset of temporal symmetry breaking in a simple repetitively driven nanoscale system.

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