Regensburg 2004 – wissenschaftliches Programm

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O: Oberflächenphysik

O 22: Hauptvortrag Hövel

O 22.1: Hauptvortrag

Dienstag, 9. März 2004, 14:45–15:30, H36

Electronic structure and morphology of supported clusters as observed by photoemission and STM/STS — •Heinz Hövel — Universität Dortmund, Experimentelle Physik I, D-44221 Dortmund

The investigation of clusters, i.e. small particles with nanometer dimensions, in contact with surfaces is a presently very active new direction of research after many years of successful work on free clusters in vacuum. Understanding their electronic structure and answering the question of how it is changed by the interaction with a surface is not only of fundamental interest but has also several important applications, for example in the fields of nano-electronics and catalysis. In general, the contact with the surface also influences the morphology of the clusters. With scanning tunneling microscopy (STM) one can measure the cluster height and the shape of facets on top of them. Scanning tunneling spectroscopy (STS) is able to probe the electronic structure of individual clusters, while photoemission averages over different sizes, isomers and orientations on the surface. Metal clusters grown in preformed nanometer sized pits on a graphite surface proved to be well suited for a combination of these different techniques on one and the same sample in ultrahigh vacuum [1]. Recently, the combination of STM/STS and photoemission, both measured at low temperatures, was used to reveal the existence of confined Shockley surface states on the (111) facets on top of gold clusters with about 10⁴ atoms [2].

[1] H. Hövel, Appl. Phys. A 72, 295 (2001).

[2] I. Barke, H. Hövel, Phys. Rev. Lett. 90, 166801 (2003).