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O: Fachverband Oberflächenphysik

O 27: Poster Session I (Methods: Scanning probe techniques; Methods: Atomic and electronic structure; Methods: Molecular simulations and statistical mechanics; Oxides and Insulators: Clean surfaces; Oxides and Insulators: Adsorption; Oxides and Insulators: Epitaxy and growth; Semiconductor substrates: Clean surfaces; Semiconductor substrates: Epitaxy and growth; Semiconductor substrates: Adsorption; Nano- optics of metallic and semiconducting nanostructures; Electronic structure; Methods: Electronic structure theory; Methods: other (experimental); Methods: other (theory); Solutions on surfaces; Epitaxial Graphene; Surface oder interface magnetism; Phase transitions; Time-resolved spectroscopies)

O 27.11: Poster

Dienstag, 24. März 2009, 18:30–21:00, P2

High Order Field Emission Resonances on W(110) and Fe/W(110) studied by Scanning Tunneling Spectroscopy — •Anika Emmenegger, Stefan Krause, André Kubetzka, Gabriela Herzog, and Roland Wiesendanger — Institute of Applied Physics, University of Hamburg, Jungiusstr. 11, 20355 Hamburg, Germany

Above metal surfaces a Rydberg-like series of states exists close to the vacuum level due to the potential well created by the attractive image potential and the surface projected bulk band gap [1]. In scanning tunneling microsopy (STM) experiments these so-called image-potential states (IPS) experience a Stark Shift [2], hence they are often called field emission resonances in this context.

Neglecting the influence of the image potential, a simple triangular potential model can be applied to determine the effective electric field in the constant current spectroscopy of IPS [3]. Whereas commercial STM electronics typically provide a maximum gap voltage of 10 V, we present scanning tunneling spectra of field emission resonances above the W(110) and Fe/W(110) surface up to the order of n=30 and voltages up to 20 V. The results will be discussed in terms of electric field determination, revealing that the assumption of a constant electric field is only applicable to voltages exceeding 10 V.

[1] U. Thomann et al., Phys. Rev. B 61, 16163 (2000).

[2] S. Crampin, Phys. Rev. Lett. 95, 46801 (2005).

[3] J. H. Coombs and J. K. Gimzewski, J. of Microsc. 125, 841 (1988).