Berlin 2015 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 84: Focus Session: Structural Dynamics in Nanoscale Materials Probed by Ultrashort Electron Pulses

O 84.1: Topical Talk

Donnerstag, 19. März 2015, 15:00–15:30, MA 005

Femtosecond electron probes for the investigation of structural dynamics and ultrafast currents in nanomaterials — •Ralph Ernstorfer, Melanie Müller, Lutz Waldecker, Roman Bertoni, Thomas Vasileiadis, and Alexander Paarmann — Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin

We investigate ultrafast structural as well as electronic dynamics in low-dimensional systems such as two-dimensional materials, one-dimensional nanowires, and nanoparticles. Such studies require femtosecond probes strongly interacting with small-volume samples. Electrons with energies ranging from 50 to 1000 eV exhibit extremely large scattering cross sections and high sensitivity to electric fields. Employing a laser-triggered point-like source of either divergent or collimated electron wave packets, we developed a hybrid approach for femtosecond point projection microscopy (fsPPM) and femtosecond low-energy electron diffraction (fsLEED) [1]. We investigate ultrafast electric currents in nanowires with sub-100 femtosecond temporal and few 10 nm spatial resolutions. This new low-energy electron technique is complemented by femtosecond transmission electron diffraction performed with 100 keV electrons. A highly compact diffractometer design allows for delivering 100 fs long pulses containing up to 5000 electrons to the sample [2]. We will discuss structural dynamics and electron-lattice interaction in confined materials such as quasi-2D materials and nanoparticles. References: [1] M. Müller et al., Nature Communications 5, 5292 (2014). [2] L. Waldecker, arXiv:1412.1942 (2014).