Berlin 2015 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 70: Structural Dynamics in Nanoscale Materials Probed by Ultrashort Electron Pulses

O 70.12: Poster

Mittwoch, 18. März 2015, 18:15–21:00, Poster A

Miniaturized photoelectron gun for ultrafast low-energy electron diffraction — •Gero Storeck, Simon Schweda, Max Gulde, Sebastian Schramm, Sascha Schäfer, and Claus Ropers — IV. Physical Institute, University of Göttingen, 37077 Göttingen, Germany

Probing structural dynamics at surfaces with high temporal resolution provides insights into a rich class of phenomena, which are unique to quasi-two-dimensional systems [1,2]. Utilizing a laser-pump/electron-probe scheme, ultrafast low-energy electron diffraction (ULEED) promises direct access to such processes, provided that the generation of well-collimated ultrashort low-energy electron pulses is achieved. Recently, nanometric photocathodes were shown to minimize spatial and temporal pulse broadening at low electron energies, resulting in a first ULEED experiment [3]. Using this experimental setup, laser-driven dynamics in a polymer/graphene bilayer were resolved with a temporal resolution of 2 ps in a transmission geometry. In a further development, we present the design of a compact pulsed electron gun allowing for ultrafast low-energy electron experiments in backscattering diffraction. First applications to graphene on silicon carbide are shown.

[1] A. Hanisch-Blicharski et al., Ultramicroscopy 127, 2-8 (2013). [2] J. M. Kosterlitz et al., J. Phys. Chem. 6, 1181-1203 (1973). [3] M. Gulde et al., Science 354, 200 (2014).