Regensburg 2007 – wissenschaftliches Programm
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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)