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O: Oberflächenphysik
O 22: Rastersondentechniken I
O 22.1: Vortrag
Samstag, 5. März 2005, 10:45–11:00, TU EB407
Long-range energy dissipation in non-contact AFM — •Domenique Weiner1,2, André Schirmeisen1,2, and Harald Fuchs1,2 — 1Physikalisches Institut, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Str. 10, 48149 Münster — 2CeNTech, Center for Nanotechnology, Gievenbecker Weg 11, 48149 Münster
The dissipated energy between tip and sample of an AFM driven in the non-contact mode is the subject of current research. The long-range dissipation and its underlying mechanisms are not well understood [1]. The dependence of the dissipation on the oscillation amplitude and the temperature can give a better insight in this effect. We are using a UHV-VT-AFM (Omicron), which enables us to get the frequency shift and the damping signal as a function of the distance between tip and sample. From these values it is possible to calculate the conservative forces and the dissipation. We apply a voltage between tip and sample to measure the electrical dissipation. We are using commercial silicon cantilevers covered with a PtIr-layer, which is about 30 nm thick to guarantee a metallic contact. The investigated Au (111) surface is sputtered and annealed under ultra-high vacuum conditions. This single crystal shows a dissipation signal, which roughly depends on the distance by the power law 1/zn where n=3.5 at RT, which is comparable to other investigations [2,3]. In particular we focus on the temperature dependence of the non-contact friction in order to understand the origin of the dissipation, which might be linked to van der Waals friction [1] or electrical dissipation [4].[1] Volokitin et al., PRL 91, 2003, [2] Gotsmann et al., PRL 86, 2001, [3] Stipe et al., PRL 87, 2001, [4] Denk et al., APL 59, 1991