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O: Fachverband Oberflächenphysik
O 10: Focus Session Ultrafast Electron Microscopy at the Space-Time Limit II
O 10.9: Vortrag
Montag, 17. März 2025, 17:30–17:45, H2
Laser-driven cold-field emission source for ultrafast transmission electron microscopy — Alexander Schröder1, •Andreas Wendeln1,2, Jonathan Weber1,2, Masaki Mukai3, Yuji Kohno3, and Sascha Schäfer1,4 — 1Department of Physics, University of Regensburg, Regensburg, Germany — 2Insitute of Physics, Carl-von-Ossietzky Universität Oldenburg, Oldenburg, Germany — 3JEOL Ltd., Tokio, Japan — 4Regensburg Center for Ultrafast Nanoscopy (RUN), Regensburg, Germany
In recent years ultrafast transmission electron microscopy (UTEM), which combines the nanometer spatial resolution of a TEM with the femtosecond temporal resolution of a pump-probe approach, has become an increasingly important tool for investigating nanoscale dynamics. Further improving the spatio-temporal resolution in time-resolved electron imaging experiments requires femtosecond photoelectron sources with a higher degree-of-coherence. Here, we present the development of a laser-driven cold field electron source integrated in a UTEM instrument [1]. This approach yields 220-fs electron pulses with electron energy widths down to 360 meV, photoelectron spot sizes of 2 Å, and a peak normalized beam brightness exceeding 6.5 · 1013 A/m2sr, providing a new level of spatial and spectral precision in observing ultrafast nanoscale dynamics for UTEM applications. Lastly, we discuss the implementation of laser-driven cold-field emitters in a probe-aberration-corrected electron microscope potentially leading to smaller spot sizes with less coherent beams and significantly increased electron currents. [1] Schröder et al., arXiv:2410.23961, (2024).
Keywords: UTEM; laser-driven linear cold-field emission; pulsed electron sources; nanoscale dynamics; brightness