Dresden 2009 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 42: Poster Session II (Nanostructures at surfaces: arrays; Nanostructures at surfaces: Dots, particles, clusters; Nanostructures at surfaces: Other; Nanostructures at surfaces: Wires, tubes; Metal substrates: Adsorption of O and/or H; Metal substrates: Clean surfaces; Metal substrates: Adsorption of organic/bio moledules; Metal substrates: Solid-liquid interfaces; Metal substrates: Adsorption of inorganic molecules; Metal substrates: Epitaxy and growth; Heterogeneous catalysis; Surface chemical reactions; Ab-initio approaches to excitations in condensed matter; Organic, polymeric, biomolecular films– also with adsorbates; Particles and clusters)

O 42.9: Poster

Mittwoch, 25. März 2009, 17:45–20:30, P2

Local spectroscopy of metallic thin layers and clusters on semiconducting surfaces — •Jedrzej Schmeidel, Mathias Mende, Christoph Tegenkamp, and Herbert Pfnür — Institut für Festkörperphysik, Leibniz Universität Hannover, Abteilung Oberflächen, Appelstrasse 2, 30167 Hannover, Germany

Many physical and chemical properties of metallic nanostructures depend strongly on their size and the coupling to their supports. Although transport concepts, like Schottky barriers and Coulomb blockade effects, are understood on a mesoscopic scale, the knowledge of influence of atomic sized defect structures (islands, steps, grains) is still lacking. Using Ag wetting layers on Si(111), we have investigated the adsorption sites and I(V) characteristics of silver clusters adsorbed at different lattice sites by means of STM and STS. Using Ag √3×√3 reconstruction on Si(111), strong band bending leads to charge depletion in Si close to the hybrid interface, i.e. the 2d template is electrically isolated. It was noticed in the I(V) curves, that the Debye length is around 100nm (10GΩ) for properly n-doped samples.
Additional evaporation of Ag followed by annealing to 300K results in the formation of nm-sized Ag clusters on top. Using the STM tip as a second tunneling junction, Coulomb blockade effects at 100K have been found in form of dI/dV resonance structures within the Si band gap range. The separation of these peaks in inversely proportional to the dot size as classically expected.