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       Session SS1-FrM

Paper SS1-FrM7
Direct Observation of Surface Alloying and Interface Roughening: Growth of Au on Fe(001)

Friday, November 2, 2001, 10:20 am, Room 120

Session: Dynamics of Metal Surfaces
Presenter: H. van Kempen, University of Nijmegen, The Netherlands
Authors: M.M.J. Bischoff, University of Nijmegen, The Netherlands
T. Yamada, University of Nijmegen, The Netherlands
A.J. Quinn, University of Nijmegen, The Netherlands
R.G.P. van der Kraan, University of Nijmegen, The Netherlands
H. van Kempen, University of Nijmegen, The Netherlands
Correspondent: Click to Email
Iron and gold belong to the family of elements which do not form alloys because of the large size difference of the Fe and Au atoms. Nevertheless, it has been predicted by Tersoff@footnote 1@ that for those elements surface confined mixing may generally occur. In the low coverage limit, this might lead to surface alloying. Because of the immiscibility of these elements, an interesting question is what will happen when this surface alloy becomes saturated, i.e. more Au is deposited than allowed for a surface confined alloy. The Au/Fe combination is especially suitable for the detailed study of possible interface processes like segregation and interface diffusion. The reason is that, while the in-plane lattice match is nearly perfect, there is a large difference in the out-of plane distance between the bcc Fe and the fcc Au (0.14 nm compared to 0.20 nm). This allows to discriminate between interface and surface features. In this paper, we report a scanning tunneling microscopy study on the growth of Au on Fe(001) at 500K. Deposition of 0.5 monolayer (ML) leads to complete coverage by a homogeneous alloyed monolayer and simultaneous formation of islands covering 50% of the terraces. Consecutive deposition of more Au leads to demixing: in this process Au islands embedded in the original Fe(001) terrace are created while Fe islands stick out in the Au covering layers. By using suitable chosen growth and anneal temperatures, the processes at the interface can be followed even for thicker coverages of 5 ML. Scanning tunneling spectroscopy studies on this system will be presented: a new surface state around 0.6-0.7 eV is detected on the homogeneous alloyed surface layer. @FootnoteText@ @footnote 1@J. Tersoff, Phys. Rev. Lett. 74, 434 (1995).