Regensburg 2007 – scientific programme

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O: Fachverband Oberflächenphysik

O 14: Metal Substrates: Epitaxy and Growth

O 14.2: Talk

Monday, March 26, 2007, 14:30–14:45, H39

Shape anisotropy of adatom islands as a probe for long range dipolar forces — •Herbert Wormeester, Frits Rabbering, Teun Warnaar, and Bene Poelsema — Solid State Physics, MESA+ Institute for Nanotechnology, University of Twente, Enschede, The Netherlands

The observation of shape anisotropy of adatom, islands obtained after grazing incidence growth of Cu on Cu(001) was explained with the steering effect. This effect describes the local variation of incident flux due to attractive interaction between the incoming atoms and the surface. High-Resolution Low Energy Electron Diffraction was used to measure the shape anisotropy as a function of coverage from 0.3 to 0.6 ML. Simulations of the growth process including an evaluation of the steering effect also show the evolution of anisotropy. The strength of the long range attractive potential as a result of dipolar interactions is in the simulation varied between absent and stronger than expected on the basis of an analysis of the optical properties of both the atom and the half infinite substrate. We found counter-intuively that a stronger long range interaction decreases the shape anisotropy. This can be explained by its influence on the flux distribution on adatom islands. Diffraction profiles evaluated for the simulated morphologies are used for comparison with experimental observations. This indicates that long range forces play a dominant role in the observed anisotropy and that their strength seems to be stronger than derived from optical properties.