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O: Fachverband Oberflächenphysik

O 15: Mini-Symposium: Ultrafast surface dynamics at the space-time limit II

O 15.2: Talk

Monday, March 1, 2021, 14:05–14:25, R1

Structural Dynamics at Surfaces: Current State and Prospects of tr-RHEED — •Christian Brand, Jonas Fortmann, Thorben Groven, Tobias Witte, Fabian Thiemann, Bernd Hafke, Mohammad Tajik, and Michael Horn-von Hoegen — Fakultät für Physik, Universität Duisburg-Essen, 47057 Duisburg

Ultrafast time-resolved reflection high energy electron diffraction (tr-RHEED) is employed to follow structural dynamics at surfaces upon fs-laser excitation. We measure the transient changes of intensity, profile and position of diffraction spots in a pump-probe setup with a temporal resolution of 350 fs. We demonstrate the broad capabilities of this technique through three examples: Electron phonon coupling and nanoscale heat transport is studied for ultrathin epitaxial Pb and Bi films through the Debye-Waller effect [1,2]. Ultrafast dynamics in the In atomic wire system on Si(111) serves as an example for a strongly driven first order phase transition (PT) [3]. The dynamics of a second order PT are observed through the order-disorder transition in the Si spin chain system on the Si(553)-Au surface [4]. We discuss future developments of this technique for improving the temporal resolution below 200 fs at increased brightness of the electron pulses, the perspectives of mode specific excitation with reduced photon energy or with THz radiation, and the combination of electron and optical probes to access transient changes of electronic properties. [1] T. Witte et al., Appl. Phys. Lett. 110, 243103 (2017); [2] V. Tinnemann et al., Structural Dynamics 6, 035101 & 065101 (2019); [3] T. Frigge et al., Nature 544, 207 (2017); [4] B. Hafke et al., PRL 124, 016102 (2020).