Berlin 2008 – scientific programme

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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 43.28: Poster

Tuesday, February 26, 2008, 18:30–19:30, Poster F

The nanoscale electrochemical potential of a current carrying surface state resolved with Scanning Tunneling Potentiometry — •Jan Homoth¹, Martin Wenderoth¹, Thomas Druga¹, Lars Winking¹, Rainer G. Ulbrich¹, Mark Kaspers², Alexander Bernhart², Bastian Weyers², Evgeny Zubkov², Rolf Möller², and Christian Bobisch³ — ¹IV. Physikalisches Institut, Georg-August-Universität Göttingen — ²University of Duisburg-Essen, Department of Physics, Duisburg, Germany — ³University of California, Irvine, USA

Charge transport through the surface state of the Si(111)√3·√3−Ag surface has been investigated with a lateral resolution of Angstroms. Across line defects like monatomic terrace steps the electrochemical potential µ_ec(x,y) varies strongly. Transport across such defects occurs as tunneling through a quantum mechanical barrier. We demonstrate that the variation in µ_ec responds linearly to the applied current density and does not depend on the local current direction. Furthermore, the variation of µ_ec does not coincide with the topography data: A lateral shift is observed and the widths differ. Using a variety of tip configurations we analyze the experimental widths and lateral shifts in detail. Comparing these results with STM-calculations, we conclude that the change of µ_ec is unaffected by tip convolution artefacts and cannot be described with a step-like change in µ_ec. A qualitative model describing the spatially dependent electron distribution and the variation of µ_ec is derived, extending the early approach of Datta. This work was supported by the DFG, SFB 602 Tp A7.