Regensburg 2016 – scientific programme

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O: Fachverband Oberflächenphysik

O 94: Ultrafast Surface Dynamics II

O 94.1: Invited Talk

Friday, March 11, 2016, 10:30–11:00, S054

Time-resolved electron microscopy: probing ultrafast processes at the nanoscale — •Sascha Schäfer — 4th Physical Institute-Solids and Nanostructures, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen

Ultrafast transmission electron microscopy (UTEM) is a promising technique for the investigation of ultrafast dynamics with nanoscale spatial resolution [1]. In UTEM, a pulsed electron beam with sub-picosecond bunch duration is utilized to stroboscopically probe laser-induced processes, using the versatile imaging and diffraction capabilities of electron microscopy. However, up to now, its applicability was limited by the coherence properties of available pulsed electron sources. In the Göttingen UTEM project, we developed nanoscale laser-driven photocathodes, which allow for the generation of highly coherent electron pulses. At the sample position, we achieve electron focal spot sizes down to a few nanometers with a pulse duration of about 300 fs. Such a tightly focused ultrafast probe enables the investigation of fast processes in heterogeneous systems and at interfaces, and I will present some first applications, including the inelastic electron scattering in optical near-fields [2], and the mapping of optically induced structural dynamics at the edge of a single-crystalline graphite membrane.

[1] A. H. Zewail, Science 328, 187-93 (2010). [2] A. Feist, K. E. Echternkamp, J. Schauss, S. V. Yalunin, S. Schäfer, C. Ropers. Nature 521, 200-203 (2015).