Dresden 2011 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 85: Poster Session II
HL 85.23: Poster
Thursday, March 17, 2011, 18:00–21:00, P4
Ultrafast X-Ray Diffraction on Photoexcited Superlattices: Simulation and Experiment — •Marc Herzog1, Daniel Schick1, Ionela Vrejoiu2, and Matias Bargheer1,3 — 1Institut für Physik und Astronomie, Universität Potsdam, Potsdam, Germany — 2Max-Planck-Institut für Mikrostrukturphysik, Halle, Germany — 3Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin, Germany
Ultrafast x-ray diffraction (XRD) is a well-suited method to monitor and hence understand the details of atomic motions in a solid-state material on its intrinsic timescales. However, the interpretation is not always straightforward. This presentation focuses on time-resolved XRD on superlattices (SL) in which photoexcited coherent acoustic phonons modulate the x-ray structure factor of various SL Bragg reflections [1]. The resulting time-dependent strain field manifests itself in transient changes of diffraction efficiencies and shifts of the Bragg angles. From the observation of transient rocking curves we can deduce the structural dynamics initiated by an optical pump pulse and thereby gain knowledge of material properties as well as excitation and coupling mechanisms. We analyze a linear-chain model to simulate the strain field and use dynamical x-ray diffraction theory to calculate the corresponding rocking curves. We identify general features of the transient x-ray reflections of such optically excited SLs and compare the predictions to experimental results. We find almost perfect agreements for a large range of linear and non-linear phenomena and different samples.
[1] Herzog et al., Appl. Phys. Lett. 96, 161906 (2010).