Berlin 2008 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 43: Poster Session II - MA 141/144 (Surface Spectroscopy on Kondo Systems; Frontiers of Surface Sensitive Electron Microscopy; Methods: Scanning Probe Techniques+Electronic Structure Theory+Other; Time-Resolved Spectroscopy of Surface Dynamics with EUV and XUV Radiation; joined by SYNF posters)

O 43.13: Poster

Dienstag, 26. Februar 2008, 18:30–19:30, Poster F

Spin-dependent Image Potential States Studied By SP-STS — •Anika Emmenegger, Stefan Krause, Gabriela Herzog, André Kubetzka, Daniel Haude, and Roland Wiesendanger — Institute of Applied Physics, University of Hamburg, Germany

An electron approaching a metal surface feels the attractive force of the polarization charge it induces in the surface region of the solid. If the surface has a band gap near the vacuum level, the electron gets trapped by its own image, confined by the surface on the one side and the slowly decaying Coulombic potential on the other side. These image-potential induced surface states (IPS) form a Rydberg-like series close to the vacuum level. Though located relatively far away from the surface, they are still sensitive to the local elctronic, atomic and magnetic surface structure.

Consequently, spin-polarized scanning tunneling spectroscopy (SP-STS) of IPS allows to investigate the magnetic surface properties on a local scale but at tip-sample distances larger than in normal tunneling experiments, thereby reducing the probability of accidental tip-sample collisions [1]. However, STS performed by commercial scanning tunneling microscopes (STM) is usually limited to a maximum bias voltage of 10V. Going beyond this limit we are able to investigate spin-dependent IPS of higher order at further increased tunneling distances.

First measurements in a high voltage regime will be presented and discussed.

[1] A. Kubetzka et al., Appl. Phys. Lett. 91, 012508 (2007).