Berlin 2018 – scientific programme
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O: Fachverband Oberflächenphysik
O 83: Poster Focus Session: Structural Dynamics in Nanoscale Materials, Probed by Ultrafast Electron Pulses
O 83.3: Poster
Wednesday, March 14, 2018, 18:15–20:30, Poster A
Picosecond acoustic waves in laser-excited metal-semiconductor heterostructures studied by ultrafast X-ray diffraction — •Fabian Brinks1, Mohammadmahdi Afshari1, Philipp Krumey1, Andrey Akimov2, Dmitri Yakovlev3, Manfred Bayer3, and Klaus Sokolowski-Tinten1 — 1Faculty of Physics and Centre for Nanointegration Duisburg-Essen, Lotharstrasse 1, 47057 Duisburg — 2School of Physics and Astronomy, University of Nottingham, NG7 2RD, UK — 3Faculty of Physics, Technical University Dortmund, 44221 Dortmund, Germany
Absorption of ultrashort optical pulses in solids leads to a quasi-instantaneous increase of stress/pressure which is subsequently released by acoustic strain waves traveling through the sample. We investigate the excitation and transient evolution of such coherent acoustic phonons in metal-semiconductor heterostructures composed of thin metal films (Ti, Cr, Al, Al, Pt, Au, Pd) deposited on 100-oriented GaAs substrates by time-resolved X-ray diffraction using ultrashort X-ray pulses at 4.5 keV from a fs laser-plasma X-ray source. By probing the GaAs (400) Bragg reflection in an optical pump - X-ray probe scheme and comparing our experimental data to dynamical diffraction calculations, we aim to develop a quantitative material-dependent understanding of the transient stress/strain evolution upon ultrafast laser excitation.