IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Surface Science Monday Sessions
       Session SS2-MoP

Paper SS2-MoP10
About the Interface between a Quasicrystal and its Oxide Overlayer

Monday, October 29, 2001, 5:30 pm, Room 134/135

Session: Surfaces and Interfaces Poster Session
Presenter: V. Fournèe, Iowa State University
Authors: V. Fournèe, Iowa State University
J.W. Anderegg, Iowa State University
A.R. Ross, Iowa State University
T.A. Lograsso, Iowa State University
P.A. Thiel, Iowa State University
Correspondent: Click to Email
When the surface of an Al-Pd-Mn icosahedral quasicrystal (QC) is exposed to air at room temperature, an almost pure alumina overlayer develops across it. The thickness of this oxide is rather small and is similar to the passivating layer on fcc-Al. This is of course an attractive characteristic which, combined with other surface properties like low friction coefficients or low adhesion, makes QC surfaces relevant for technological applications.@footnote 1@ In particular, the low adhesion property, related to a low surface energy, is believed to be influenced by the gradient, through the surface, of the electronic density of states at the Fermi level (N(EF)). This assume that the low N(EF) characteristic of the bulk electronic structure of QC is effectively maintained up to the surface. However, in a practical situation where an aluminium oxide overlayer is formed, the interface just under the oxide may be depleted in Al and enriched in Pd and Mn. The concentration may be shifted out of the stability range of the QC phase and structural transformation may occur. This also should affect the electronic properties at the interface. In an effort to clarify this point, we will present our recent experimental results on this subject. Experiments were performed on a five-fold surface of a single grain Al-Pd-Mn icosahedral QC. The clean surface was prepared in UHV and later oxidized in-situ. A depth profile of the chemical composition across the oxidized surface is acquired both by Auger and photoelectron spectroscopies. Informations on the morphology of this surface are derived from both scanning electron and scanning tunneling microscopies. Finally, an analysis of the photoelectron core-level lineshape, as a function of the escape depth of the photoelectrons, provides insight into the variations of the metallic character through the surface. @FootnoteText@ @footnote 1@ P.A. Thiel, C. J. Jenks, A. I. Goldman, in Physical properties of Quasicrystals, ed. Z. Stadnik (Springer Verlag, Berlin, 1999).