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O: Fachverband Oberflächenphysik

O 14: Metal Substrates: Epitaxy and Growth

O 14.6: Talk

Monday, March 26, 2007, 15:30–15:45, H39

Strain relief within thin films of Co and Ni on unreconstructed Ir(100) — •Wolfgang Meyer, Andreas Klein, Lutz Hammer, Stefan Müller, and Klaus Heinz — Lehrstuhl für Festkörperphysik, Universität Erlangen-Nürnberg, Staudtstr. 7, D-91058 Erlangen

As reported earlier, Co and Ni grows layerwise and pseudomorphically on the unreconstructed Ir(100) surface up to a thickness of at least five monolayers despite the large lattice misfit of about 8 % between Co/Ni and Ir. However, STM shows that the films are atomically flat only up to two monolayers, while thicker films show surface corrugations in the range 0.1 - 0.3 Å increasing in amplitude and frequency with film thickness. Moreover, LEED intensity analyses reveal large atomic displacements within the whole volume of the films much beyond usual thermal vibrations. Consistently, film layer spacings derived from LEED are somewhat larger than predicted from DFT calculations for ideal films. We interpret these displacements as the onset of a strain relief mechanism, a picture, which is also corroborated by surface stress measurements performed elsewhere [1]. The nature of this mechanism is discussed in detail on the basis of both the available experimental data as well as DFT model calculations.

[1] C. Tian, D. Sander, J. Kirschner, MPI Halle, unpublished.