Dresden 2006 – wissenschaftliches Programm
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O: Oberflächenphysik
O 14: Poster session I (Adsorption, Epitaxy and growth, Phase transitions, Surface reactions, Organic films, Electronic structure, Methods) (sponsored by Omicron Nanotechnology GmbH)
O 14.57: Poster
Montag, 27. März 2006, 18:00–21:00, P2
Ab-initio calculation of STM images of Si(111)-(2x1) and of PTCDA:Ag(111) — •Michael Rohlfing1, J. K. Garleff2, A. Kraft3, S. K. M. Jönsson1, F. S. Tautz1, R. Temirov1, R. G. Ulbrich2, and M. Wenderoth2 — 1International University Bremen, School of Engineering and Science, Bremen, Germany — 24. Physikalisches Institut, Universität Göttingen, Germany — 3Institut für Mess- und Regelungstechnik, Universität Hannover, Germany
We discuss the calculation of STM images on the basis of ab-initio electronic-structure theory, employing the approach of Tersoff and Hamann. One of the key ingredients is the careful evaluation of electronic wave functions up to 10 Angstrom outside the surface. To this end, we calculate each wave function close to the surface, take its two-dimensional Fourier transform, and extrapolate each Fourier component to the height of the tip, allowing to evaluate the LDOS and resulting tunneling current at the tip position. In the case of the Si(111)-(2x1) surface the two dangling-bond surface bands lead to high-contrast STM features with characteristic spatial shifts between both bands, as we also observe in experiment [1]. In the case of a monolayer of PTCDA on Ag(111), high-resolution images are obtained in theory and experiment, as well, allowing for an accurate determination of adsorption sites and for a systematic comparison between theory and experiment regarding trends with varying tip height and voltage.
[1] J. K. Garleff, M. Wenderoth, K. Sauthoff, R. G. Ulbrich, and M. Rohlfing, Phys. Rev. B 70, 245424 (2004).