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O: Fachverband Oberflächenphysik
O 56: Metal substrates: Epitaxy, growth and adsorbates
O 56.4: Vortrag
Donnerstag, 26. März 2009, 15:45–16:00, SCH A316
The temperature dependence of film stress in epitaxial Co monolayers on Pt(111) — •Safia Ouazi1,2, Zhen Tian2, Anita Dhaka2, Dirk Sander2, Harald Brune1, and Jürgen Kirschner2 — 1Institut de Physique des Nanostructures, EPFL, Station 3, CH-1015 Lausanne, Switzerland — 2Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle, Germany
We perform combined stress and low energy electron diffraction (LEED) studies to investigate the correlation between film strain and stress during the deposition of several monolayer thin Co films on Pt(111) in the temperature range 250 to 400 K. The quantitative analysis of our cantilever stress measurements indicates a tensile stress of +4.3 GPa in the thickness range between 3 to 7 ML for the investigated growth temperature range. LEED indicates a Moiré-like diffraction pattern, where our quantitative analysis of the in-plane lattice spacing gives a film strain of +1.2% from 1 to 7 ML. We apply continuum elasticity and calculate +5 GPa for the strain-induced film stress, in close agreement with the experimental value. In thinner films, the measured film stress is found to depend sensitively on the growth temperature. We ascribe this strong temperature dependence of the initial stress to the thermally activated Co incorporation into Pt, which relieves surface stress. We discuss our results in view of STM [1], LEED [2], and SXRD[3] studies, and indicate the implication of Pt-Co intermixing for the magnetic anisotropy of this system.
[1] Varga et al., phys. Stat. sol. 187 (2001) 97 [2] Tsay et al., Surf. Sci. 96 (1998) 313 [3] Ferrer et al., Phys. Rev. B 56 (1997) 9848