Berlin 2018 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 1: Layer Properties: Electronic, Optical and Mechanical

DS 1.6: Vortrag

Montag, 12. März 2018, 10:45–11:00, H 0111

Layer specific observation of the slow thermal equilibration in ultrathin metallicnanolayers by femtosecond x-ray diffractionJan-Etienne Pudell1, Alexey Maznev2, Marc Herzog1, Matthias Kronseder3, Christian Back3, Gregory Malinowski4, •Alexander von Reppert1, and Matias Bargheer1,51Institut für Physik und Astronomie, Universität Potsdam, Potsdam, Germany — 2Department of Chemistry, Massachusetts Institute of Technology, Massachusetts, USA — 3Institut für Experimentelle und Angewandte Physik, Universität Regensburg, Germany — 4Institut Jean Lamour (UMR CNRS 7198), Université Lorraine, Nancy, France — 5Helmholtz-Zentrum Berlin, Berlin, Germany

We study the ultrafast response of nanometric layers of Gold (Au) on Nickel (Ni) upon optical excitation with femtosecond laser pulses by ultrafast x-ray diffraction (UXRD). We show the experimental results obtained by exciting a 12 nm Ni film through a 5 nm Au film by 800 nm pulses with about 50 fs pulse duration. Although the pump pulse impinges on Au, the initially deposited energy is essentially transferred to the Ni lattice due to its much larger electron phonon-coupling constant. The most surprising result is the very slow heat transport from Ni into the Au lattice. The Au lattice temperature reaches its maximum only after 80 ps, although bulk heat conductivity estimates would predict less than 1 ps to equilibrate the temperatures of the two ultrathin metal layers. UXRD thus represents a formidable experimental probe to support theoretical developments in nanoscale thermal transport.

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