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O: Fachverband Oberflächenphysik

O 17: Poster Session I (Nanostructures at Surfaces; Metal Substrates: Epitaxy and Growth; Methods: Scanning Probe Techniques; Phase Transitions)

O 17.57: Poster

Montag, 26. März 2007, 17:30–20:30, Poster C

Dynamic Force Spectroscopy on Gadolinium Islands epitaxially grown on W(110) — •Rene Schmidt, Alexander Schwarz, and Roland Wiesendanger — Institut für Angewandte Physik, Universität Hamburg,

Gd/W(110) is prepared in UHV by evaporating gadolinium onto a clean tungsten substrate. Additional annealing leads to the growth of Gd islands on a base Gd-wetting layer. Atomic force microscopy in the dynamic mode using the frequency modulation technique (FM-AFM) and a Gd coated tip is employed for imaging these islands. Some parts of the Gd-islands are covered by hydrogen, which is the main compound present in the residual gas of the UHV-system. Hydrogen locally alters the work function of the Gd islands¹ and can therefore be distinguished by bias spectroscopy. Moreover, the application of dynamic force spectroscopy enables to quantify the complex interaction of the different surface species on a local scale. With the focus on the distance dependence of the forces between tip and surface, we perform single Δ f(z)-curves while retracting into the long-range regime and single curves and spectroscopy fields whilst approaching the surface. As all the curves are taken with varying amplitudes due to the feedback regulation, the force-calculation uses a formalism given by Schirmeisen et al². A model of the tip-surface interaction potential allows to fit the force-distance-curves and to determine the influence of the hydrogen on the tip-sample force.

¹ M. Getzlaff et al., Phys. Rev. B 59, 8195 (1999)

² A. Schirmeisen et al., Nanotechnology 16, S13 (2005)