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O: Fachverband Oberflächenphysik

O 34: Methods: Atomic and Electronic Structure I

O 34.3: Vortrag

Dienstag, 27. März 2007, 16:15–16:30, H42

Scanning Tunneling Spectrocsopy of image potential states on NaCl/Ag(100) — •Hans-Christoph Ploigt, François Patthey, and Wolf-Dieter Schneider — Ecole Polytechnique Fédérale de Lausanne, Institut de physique des nanostructures, CH-1015 Lausanne, Switzerland

Image potential states are important two-dimensional electronic states at surfaces the binding energy of which reflects the nature of the substrate, especially the presence of adsorbates. These states are probed by Scanning Tunneling Spectroscopy. We prepared Ag(100) samples which are partially covered by NaCl islands of different thickness and measured dI/dV spectra with closed feedback loop at 50 K and 5 K with different tips (W, PtIr, Ni). The spectra on clean Ag(100) are reproduced with a simple one-dimensional model which includes the electric field of the tunnel junction. In this way, the work function and the radius of curvature of the tip have been determined and introduced as fixed parameters in a 1D model which includes a dielectric layer to calculate the spectra on NaCl/Ag(100). The resulting good agreement between simulation and experiment allows us to extract from the shift of the image potential/field emission states between clean Ag(100) and NaCl covered Ag(100) the work function change of the sample.