Regensburg 2022 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 25: Poster 1
HL 25.66: Poster
Wednesday, September 7, 2022, 18:00–20:00, P2
Lattice thermal expansion of as-grown GaAs nanowires due to optical excitation measured by X-ray pump probe experiment — •Taseer Anjum1,2, Francisca Largo2, Waheed Salehi1, Matthias Rössle3, Oliver Brandt2, Lutz Geelhaar2, and Ullrich Pietsch1 — 1Festkörperphysik, Universität Siegen, Siegen, Germany — 2Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e.V., Berlin, Germany — 3Helmholtz-Zentrum Berlin für Materialien und Energie, Wilhelm-Conrad-Röntgen Campus, BESSY II, Berlin, Germany
We investigated the transient structural response in the ensemble of AlxIn1-xAs/GaAs core-shell NWs, grown on Si (111) substrate when irradiated with femtosecond laser pulses via x-ray pump-probe experiment at KMC3-XPP & P08 beamlines of Bessy II & PETRA III respectively. Femtosecond laser irradiation of solids excites photoelectrons from valance band to conduction and triggers a cascade of fundamental dynamical processes that occur on the picosecond to nanosecond time scales such as excitation and thermal equilibration of phonons. We observe a linear behavior of strain and temperature for the first few hundreds of picoseconds followed by the thermal relaxation up to few ns. Thinner NWs cool down slowly in comparison to thicker NWs which suggests a direct dependence of thermal conductivity on the diameter. Through time-resolved x-ray pump-probe experiments we identified the thermal relaxation processes and the dynamics of the structural response of two NW samples.