Regensburg 2004 – wissenschaftliches Programm

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O: Oberflächenphysik

O 28: Postersitzung (Elektronische Struktur, Grenzfläche fest-flüssig, Halbleiteroberflächen und -grenzflächen, Magnetismus und Symposium SYXM, Methodisches, Nanostrukturen, Oberflächenreaktionen, Teilchen und Cluster, Zeitaufgelöste Spektroskopie)

O 28.68: Poster

Mittwoch, 10. März 2004, 16:00–19:00, Bereich C

STM/STS on large silver clusters at germanium (001) — •Karl-Ludwig Jonas, Armin Kleibert, Fanny Geisler, Ralf-Peter Methling, Joachim Bansmann, Viola von Oeynhausen und Karl Heinz Meiwes-Broer — Fachbereich Physik, Universität Rostock, Universitätsplatz 3, D-18051 Rostock

Cluster deposition is used to create metal-nanodots with a high aspect ratio. We present scanning tunneling spectroscopy (STS) measurements on isolated silver clusters at germanium (001). The clusters are generated using an arc cluster ion source (ACIS), mass selected and deposited under soft landing conditions (E_kin/atom < 0.5eV). Before performing STM experiments the cluster structure has been investigated using TEM, electron diffraction and EDX. Particle diameters between 5 and 14 nm have been used for the present studies. Scanning tunnelling microscopy images of large clusters always contain considerable tip folding at the steep cluster edges. Beside the accurately measured cluster height the imaging of particles of this height is therefore restricted to cluster facets at the top. Using STM and STS on deposited silver clusters structural and electronic properties are observed. In contrast to silver islands grown on germanium (001) the orientation of the crystal lattice is not fixed if cluster melting is neglected. However, some of the clusters show hexagonal facets at the top. STS is sensitive to occupied and unoccupied states near the Fermi level and reveals the existence of distinct states in the tunneling conductivity of the substrate as well as on the clusters. Thus, the richly structured density of states of the germanium (001) surface has been discovered and serves as STM/STS condition test.