Regensburg 2010 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 41: Poster Session I (Semiconductor Substrates: Epitaxy and growth; Semiconductor Substrates: Adsorbtion; Semiconductor Substrates: Solid-liquid interfaces; Semiconductor Substrates: Clean surfaces; Oxides and insulators: Epitaxy and growth; Oxides and insulators: Adsorption; Oxides and insulators: Clean surfaces; Organic, polymeric and biomolecular films - also with adsorbates; Organic electronics and photovoltaics, Surface chemical reactions; Heterogeneous catalysis; Phase transitions; Particles and clusters; Surface dynamics; Surface or interface magnetism; Electron and spin dynamics; Spin-Orbit Interaction at Surfaces; Electronic structure; Nanotribology; Solid/liquid interfaces; Graphene; Others)

O 41.60: Poster

Dienstag, 23. März 2010, 18:30–21:00, Poster B1

Thermal Boundary Conductance of Bi/Si-Heterolayers: An Ultra-Fast Time-Resolved Electron Diffraction Study — •Simone Möllenbeck, Anja Hanisch-Blicharski, Annika Kalus, Boris Krenzer, Martin Kammler, and Michael Horn-von Hoegen — Department of Physics and Center for Nanointegration Duisburg-Essen (CeNIDE) Universität Duisburg-Essen, D-47057 Duisburg, Germany

The transient heating and cooling of hetero epitaxial thin film systems after fs-laser excitation with ps time resolution was studied by means of ultra fast time resolved electron diffraction in a grazing reflection geometry (RHEED). Diffraction patterns taken at different delays between pumping laser pulse and probing electron pulse are converted to the film temperature using the Debye-Waller effect. We present results on ultra thin epitaxial Bi(111) films on Si(001) and Si(111) substrates. For a 6 nm thin Bi-film a rapid increase of the surface temperature from 80 K up to 190 K upon laser excitation is followed by a slow exponential decay with a decay constant of 640 ps which is dominated by total internal reflection of the phonons at the hetero interface between film and substrate. A linear dependence, as predicted by the theoretical models, between film thickness and decay constant can be observed for the Bi-films on Si(111) down to 2.5 nm thickness. In contrast to this we observe a constant cooling rate for the Bi/Si(100) system for films thinner than 6 nm. The extreme low cooling rate for these thin films is determined not longer by the travel time through the film but by the mean free path of the phonons.