Regensburg 2019 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 45: Poster Tuesday: Ultrafast Processes

O 45.8: Poster

Dienstag, 2. April 2019, 18:00–20:00, Poster D

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-Tinten11Faculty of Physics and Center for Nanointegration Duisburg-Essen, University of Duisburg-Essen, Lotharstrasse 1, 47048 Duisburg, Germany — 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, 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 we are able to monitor the strain waves. To reveal the underlying physical processes we follow a combined approach. Direct reconstruction of the strain profile together with simulation of the elastic wave equation followed by dynamical diffraction calculations give a complementary view on the material-dependent evolution of stress/strain upon ultrafast excitation.

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