Berlin 2008 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 42: Layer Growth: Evolution of Structure and Simulation
DS 42.4: Vortrag
Freitag, 29. Februar 2008, 17:00–17:15, H 2032
Does ion beam divergence affect pattern formation by surface sputtering? — •Taha Yasseri1, Emmanuel O. Yewande2, Alexander K. Hartmann3, and Reiner Kree1 — 1Institute for Theoretical Physics, University of Göttingen, Friedrich-Hund Platz 1, D-37075 Göttingen, Germany. — 2Department of Computing and Mathematics, Manchester Metropolitan University, John Dalton Building, Chester Street, Manchester M1 5GD, United Kingdom — 3Institut for Physics, University of Oldenburg, Carl-von-Ossietzky Strasse 9-11, 26111 Oldenburg, Germany.
In recent works on creating patterns like quantum dots or ripples via ion-beam surface sputtering, the importance of beam divergence for the creation of clear patterns is emphasized. Motivated by these experiments, we perform a (2+1)- dimensional Monte Carlo simulations of surface sputtering to study the influence of beam divergence on dynamics of pattern formation. We explain our results using linear continuum theory via evaluating the rate of growth for different modes. Generally beam divergence leads to a combination of different growth rates which slows down pattern formation. We find two exceptional situations where ion beam divergence may improve the quality of patterns. (1) Ion incidence perpendicular to the surface and (2) ion incidence around the critical angle where the orientation of formed ripples changes by 90 degrees. In case (1) anisotropic beam profiles with divergence may lead to ripples whereas isotropic profiles mainly affect the length scale of the formed dots. In case (2) non-zero beam divergence leads to patterns consisting of crossed ripples.