Dresden 2003 – wissenschaftliches Programm

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O: Oberflächenphysik

O 8: Teilchen und Cluster

O 8.3: Vortrag

Montag, 24. März 2003, 15:30–15:45, HSZ/02

Tunneling transport through silver islands on germanium (001) — •Karl-Ludwig Jonas, Viola v. Oeynhausen, and Karl Heinz Meiwes-Broer — Fachbereich Physik, Universität Rostock, Universitätsplatz 3, D-18051 Rostock

Scanning Tunneling Spectroscopy (STS) is sensitive to the surface state density around Γ. In the case of the reconstructed germanium (001) (2x1) surface this DOS is known from various band structure calculations. The Ge(001) surface DOS is determined by the dimer structure, its bonding and antibonding states. In contrast to the bulk state density no distinct gap is found and the existence of sharp and pronounced surfaces states are pointed out. This agrees with our STS measurements.

Silver clusters and islands are grown by atomic deposition on germanium. Depending on deposition amount and substrate temperature different particle densities, sizes and shapes can be achieved. STS spectra of the silver particles have no similarity to germanium spectra. Two fundamentally differing types of islands have been observed so far. First, small cluster-like aggregates show complicated spectra containing many peaks and a small gap respectively a blocked tunneling current around the fermi level. Second, for larger islands of more than three monolayers in height, less peaks are clearly resolved and the tunneling conductivity drops to a finite value at the fermi level.