Dresden 2009 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 27: Poster Session I (Methods: Scanning probe techniques; Methods: Atomic and electronic structure; Methods: Molecular simulations and statistical mechanics; Oxides and Insulators: Clean surfaces; Oxides and Insulators: Adsorption; Oxides and Insulators: Epitaxy and growth; Semiconductor substrates: Clean surfaces; Semiconductor substrates: Epitaxy and growth; Semiconductor substrates: Adsorption; Nano- optics of metallic and semiconducting nanostructures; Electronic structure; Methods: Electronic structure theory; Methods: other (experimental); Methods: other (theory); Solutions on surfaces; Epitaxial Graphene; Surface oder interface magnetism; Phase transitions; Time-resolved spectroscopies)

O 27.117: Poster

Dienstag, 24. März 2009, 18:30–21:00, P2

Ultrafast Excitation and Deexcitation Dynamics of Adsorbates on Si-Surfaces: A Time Resolved Electron Diffraction Study — •Simone Möllenbeck, Anja Hanisch-Blicharski, Tobias Pelka, Paul Schneider, Martin Kammler, Boris Krenzer, and Michael Horn-von Hoegen — Department of Physics and Center for Nanointegration Duisburg-Essen (CeNIDE) Universität Duisburg-Essen, D-47057 Duisburg, Germany

We have set up an experiment for ultra fast electron diffraction. The surface sensitivity in a RHEED (reflection high energy electron diffraction)-geometry was used to analyze the structural dynamics on a ps-timescale upon excitation by fs-laserpulses. In the past we have shown that the nanoscale heat transport in heterolayers can be studied with TR-RHEED utilizing the Debye-Waller Effect. Here we used the unique possibilities of TR-RHEED to study monolayer adsorbate systems on Silicon. As an example we present time resolved measurements of the (√3×√3) Pb/Si(111) adsorbate system. Pb was deposited on Si(111)-(7×7) at 100K. By desorption at 500K, the coverage was reduced to a (√3×√3) reconstructed Pb adsorbate system with the coverage of 1 monolayer. We observed the transient surface temperature evolution of the Pb adsorbate system after excitation with a fs-laserpulse.The measured time constant for the cooling process is 150ps. This observation agrees well with a simple theoretical model. We may present further new results to other adsorbate systems.