Dresden 2006 – scientific programme

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O: Oberflächenphysik

O 20: Epitaxy and growth II

O 20.2: Talk

Tuesday, March 28, 2006, 11:30–11:45, WIL B321

surface Debye Temperatur of thin Bi(111) on Si(001) — •Rabih Khanafer, Andreas Janzen, Boris Krenzer, Giriraj Jnawali, Hichem Hattab, and Michael Horn-von Högen — Universität-Duisburg-Essen, Institut für experimentelle Physik, 47057 Duisburg

Experiments with time resolved electron diffraction at surfaces require materials with a low surface Debye temperature to ensure high sensitivity for transient surface temperature changes upon excitation by ultrashort laser pulses. In order to study the heat dissipation in thin films from monolayer thickness up to bulk properties additionally require high quality heteroepitaxial growth. Bismuth films on Si(001) act as ideal model system for such investigations.

Bismuth with a bulk Debye temperature of 119 K shows a surface Debye temperature of only 48 K [1].Deposition of Bismuth at room temperature on Si(001) results in the formation of continuous, smooth and well oriented Bi(111) films even for a thickness as low as 3 nm. The surface Debye temperature has been determined by LEED, SPA-LEED and RHEED as function of film thickness and electron energy. Between 80 and 100 eV a decrease of the surface Debye temperature from 46 K to 33 K is observed followed by an increase to 48 K at 190 eV. This behaviour agrees well with the maximum of surface sensitivity around 100 eV.

The use of these films in a ultrafast electron diffraction experiment will be presented.

[1] R. M. Goofman, G. A. Somorjai, J. Chem. Phys. 52, 6325 (1970).