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E. Klein, B. Schwarz, C. Eisenmenger-Sittner, C. Tomastik, P.B. Barna, A. Kovács:
"The initial states of wetting and spreading of Sn and Al surface";
Vacuum, 80 (2005), 1-3; 74 - 80.

The initial states of wetting and spreading of Sn on Al surfaces

E. Klein a, B. Schwarz a, C. Eisenmenger-Sittner a, C. Tomastik b, P.B. Barna c and A. Kovács c

a Institut für Festkörperphysik, E-138, TU Wien, Wiedner Hauptstrasse 8-10, A-1040 Wien, Austria
b Institut für Allgemeine Physik, E-134, TU Wien, Wiedner Hauptstrasse 8-10, A-1040 Wien, Austria
c Research Institute for Technical Physics and Material Science, H-1121 Budapest, Hungary

Available online 2 September 2005

Abstract:
Tin (Sn) deposited on polycrystalline aluminium (Al) surfaces shows a Stranski-Krastanov growth mode which means that before Sn islands nucleate a thin Sn wetting layer is formed. If the wetting layer is removed from the Al surface by sputter cleaning in UHV it reforms by a solid state wetting process.
The sources of the Sn atoms forming the wetting layer are the Sn islands, which are not removed from the Al surface due to their size. Nonetheless, it was observed that not every island acts as an Sn emitter.
In this work, we show that this selective Sn emission is a consequence of the chemical composition and the crystallographic structure of the Sn islands. Regarding the chemical composition of the Sn islands each residual trace of oxygen has to be removed to facilitate the emission of Sn atoms from the island boundaries. In addition wetting is only initiated if the sputter cleaning process results in a visible damage of the islands, thus increasing the roughness of their surface. From this rough interface Sn atoms can emerge more easily than from a crystallographically smooth surface due to their lower coordination.
By monitoring line scans obtained from scanning auger electron spectroscopy the diffusion coefficient of the Sn atoms could be estimated from the progress of the rim of the wetting layer around the islands.

Keywords: Vapor deposition; Wetting; Spreading; Surface diffusion; Kinetic Monte-Carlo

http://aleph.ub.tuwien.ac.at/F?base=tuw01&func=find-c&ccl_term=AC05938080

http://dx.doi.org/10.1016/j.vacuum.2005.07.036