Berlin 2012 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 47: [DS] Micro- and nanopatterning (jointly with O)
O 47.3: Vortrag
Mittwoch, 28. März 2012, 12:15–12:30, H 0111
Is silicide formation the decisive factor in impurity induced ion beam pattern formation? — Sven Müller1, •Martin Engler1, Frank Frost2, and Thomas Michely1 — 1II. Physikalisches Institut, Universität zu Köln, Cologne, Germany — 2Leibniz-Institut für Oberflächenmodifizierung e.V., Leipzig, Germany
Metal co-deposition during ion beam erosion of Si induces nanoscale patterns. Here we present the results of a comparative study of Pd and Ag co-deposition during 2 keV Kr+ ion irradition of Si(001) at normal incidence. Co-deposition was conducted by e-beam evaporation and by sputter deposition from an adjacent target, which was hit by the eroding ion beam simultaneously with the Si surface.
The collision kinetics of Ag and Pd are almost identical due to their similar atomic masses (Ag: 107.9 amu, Pd: 106.4 amu) and nuclear charges (Ag: Z = 47, Pd: Z = 46). There should be differences in pattern formation If chemistry is of relevance it, since Ag is almost insoluble in Si and forms no silicides, while Pd forms a number of silicides with substantial enthalpy of formation.
We find that for Ag co-deposition no patterns are formed while a sequence of patterns forms for Pd co-deposition which depends strongly on the flux ratio of arriving Pd atoms to Kr+ ions.
Most surprising, pattern formation with Pd not only ceases for low, but also for high flux ratios. We therefore speculate that under the conditions used, phase separation through spinodal decomposition triggers the formation of the most pronounced patterns.