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DS: Fachverband Dünne Schichten

DS 48: Ion Interactions with Nano Scale Materials III (Focused Session -- Organisers: Diesing, Facsko)

DS 48.4: Talk

Thursday, March 17, 2011, 17:00–17:15, GER 37

Shadowing in metal assisted ion beam patterning on Si(001) — •Sven Macko¹, Martin Engler¹, Frank Frost², and Thomas Michely¹ — ¹II. Physikalisches Institut, Universität zu Köln, Germany — ²Leibniz-Institut für Oberflächenmodifizierung e. V., Leipzig, Germany

At grazing incidence low energy ion beam erosion of Si surfaces gives rise to nanoscale surface patterning. Co-sputterdeposition of stainless steel expands the angular range of pattern formation also to non-grazing and normal directions of incidence. Here we employ co-evaporation instead of co-sputterdeposition and a 2 keV Kr⁺ ion beam under UHV conditions. Due to the thermal energy and well defined angle of incidence of the co-evaporated species the experiments provide a more direct insight to pattern formation mechanisms. In dependence of the atom-to-ion arrival ratio we find the flat surface as well as dot and ripple patterns. Fluence dependent experiments show that the type of pattern is already selected in the early stages of pattern formation. A key parameter for pattern formation is the angle α between the impinging ion beam and the co-deposition flux. For α > 90^∘ we observe rapid formation of a faceted and rough pattern while for small angles α ≈ 30^∘ pattern formation diminishes. We conclude that shadowing is of decisive importance for the formation of local impurity concentration inhomogeneities which in turn cause local sputtering yield variations and thus the destabilization of the surface.