Regensburg 2007 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 24: Semiconductor Substrates: Epitaxy and Growth

O 24.1: Vortrag

Dienstag, 27. März 2007, 11:15–11:30, H39

Ultrafast Electron Diffraction of epitaxial Bi(111) films on Si(001) — •Anja Hanisch, Boris Krenzer, and Michael Horn-von Hoegen — Universität Duisburg-Essen, Experimentalphysik, 47057 Duisburg

Ultrafast time resolved electron diffraction experiments in a RHEED geometry allow the observation of the surface temperature evolution after laser excitation. Diffraction patterns of epitaxially Bi(111)-films grown on Si(001) taken at different delays between pumping laser pulses and probing electron pulses are converted to the transient surface temperature using the Debye-Waller effect. A rapid increase of the surface temperature from 80 K up to 190 K is followed by a slow exponential decay with a decay constant of 640 ps for 5,5 nm thin film [1], which is determined by the thermal boundary resistance at the interface between Bi and Si. While the decay constant is almost independent of the pump energy (fluence ramping from 0,33 mJ/cm2 to 3 mJ/cm2) we observe a linear dependence of the decay constant with the filmthickness for filmthicknesses between 6 nm and 12 nm. A detailed analysis shows that this linear behaviour cannot be explained in terms of existing models describing the thermal boundary resistance. In order to explain the observed behaviour the existing models have to be expanded which will be presented in this talk.

[1] A.Janzen et al., Surface Science 600, 4094 (2006).