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O: Fachverband Oberflächenphysik

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

O 70.13: Poster

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

Lattice response with respect to the orientation of the crystal to the femtosecond laser excitation observed by time-resolved electron diffraction — Carla Streubühr, •Ping Zhou, Manuel Ligges, Klaus Sokolowski-Tinten, Thomas Payer, Frank Meyer zu Heringdorf, and Michael Horn-von Hoegen — Fakultät für Physik und Zentrum für Nanointegration, Universität Duisburg-Essen

One of the fundamental questions in the field of ultrafast structural dynamics is the time scale for the energy transfer between the electron and phonon subsystem of a solid after femtosecond optical excitation. For crystalline materials, especially for layered materials like graphite or most of superconductors, the material properties depend strongly on the symmetries of the crystals. The excitation and relaxation of the lattice cannot be treated as symmetrical. The advantage of electron diffraction is the ability to map many diffraction orders at the same time and, thus, obtain rich structural information. We present here results of time resolved electron diffraction experiments on Bismuth and Nickel membranes to demonstrate the difference of the energy transfer of hot electrons to the lattice depending on the direction of the displacements. Besides the disordered thermal displacement, strain waves can be generated. They propagate between the surfaces and influence on the diffraction intensity in different way depending on the materials and the diffraction geometries. By using a simple model we could extracted strain wave information from the disordered thermal displacement and get the frequency and damping of the strain wave.