SKM 2021 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 13: Poster Session III

HL 13.20: Poster

Tuesday, September 28, 2021, 13:30–16:30, P

Space-charge effects in high-coherence electron pulses — •Alexander Schröder, Christopher Rathje, Niklas Müller, Jonathan Weber, Nora Bach, and Sascha Schäfer — Institute of Physics, University of Oldenburg, Germany

Ultrafast transmission electron microscopy (UTEM) enables the imaging of ultrafast nanoscale dynamics, utilizing an optical-pump/electron-probe approach within a high-resolution transmission electron microscope [1]. The spatio-temporal resolution in this technique sensitively depends on the phase-space structure of the employed ultrashort electron pulses. Whereas needle-shaped photoemitters were demonstrated to deliver high-coherence electron pulses in the single-electron regime, at larger bunch charges significant Coulomb interactions within the pulse need to be considered [2].

Using the newly constructed Oldenburg UTEM, we investigate the impact of Coulomb interactions on the longitudinal phase-space structure of electron pulses. Depending on the illumination intensity on the photoemitter, we observe a fluence-dependent shift and broadening of the electron energy distribution which is compared to a multiparticle simulation taking into account the expanding electron pulse close to the emitter tip. The impact of the initial electron energy after photoemission, the acceleration field and the bunch charge on the spatio-temporal electron pulse structure at the sample are discussed.

[1] A. Feist et al., Ultramicroscopy, 176, 63 (2017)

[2] N. Bach et al., Structural Dynamics 6, 014301 (2019)