Regensburg 2010 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 13: Semiconductor substrates: Adsorption

O 13.4: Vortrag

Montag, 22. März 2010, 15:45–16:00, H34

Adsorption of metalorganic molecules on metal-semiconductor systems — •Jȩdrzej Schmeidel, Christoph Tegenkamp, and Herbert Pfnür — Institut für Festkörperphysik, Leibniz Universität Hannover, Abteilung Atomare und Molekulare Strukturen, Appelstrasse 2, 30167 Hannover, Germany

Molecular junctions appropriate for transport trough single molecules can be realized using concepts of surface science. The controlled opening of ultra-thin Ag nanostructures on Si surfaces by electromigration and injection of single ferrocene molecules has been demonstrated recently [1]. In order to model accurately the conductivity of ferrocene-1,1’-dithiol molecules, thiolate bounded molecules are adsorbed on perfect sites of the Ag contacts. However, chemisorption takes place at defect sites, e.g. atomic step [2]. For an detailed understanding of this complex scenario we have investigated the adsorption of metal organic molecules on metal/semiconductor surfaces. As substrate the Ag √3 reconstruction, Ag islands and Ag multilayers on Si(111) have been investigated by means of STM and STS. Only without the wetting layer, Ag nanostructures can be electronically decoupled from the substrate as seen by a Coulomb blockade oscillations of the double barrier structure [3]. In order to study the selectivity of defects regarding molecular adsorption, porphyrins and ferrocene-1,1’-dithiol molecules have been adsorbed on these structures. The molecules adsorb predominantly at defects sites, e.g. steps and grain boundaries, as observed in the bias dependence of the STM image contrast.
[1] APL 89, 063120, [2] JCP 128, 064704, [3] PRB 80, 115304