Dresden 2003 – wissenschaftliches Programm

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O: Oberflächenphysik

O 12: Postersitzung (Struktur und Dynamik reiner Oberfl
ächen, Grenzfl
äche fest-flüssig, Nanostrukturen, Teilchen und Cluster, Halbleiteroberfl
ächen und Grenzfl
ächen, Zeitaufgelöste Spektroskopie, Rastersondentechniken, Methodisches)

O 12.20: Poster

Montag, 24. März 2003, 18:00–21:00, P1

Heterogeneous nucleation and growth of metal nanoparticles on WSe2 and WS2 — •Jörg Zimmermann, Alexander C. Müller, Laurent Helden, Johannes Boneberg, and Paul Leiderer — University of Konstanz, Fachbereich Physik, 78457 Konstanz

In general there are three different modes for one material (e.g. a metal) to grow on a substrate. In our case evaporation of sub-monolayer amounts of metals on weakly interacting so-called van der Waals surfaces like layered semiconductors WSe2 or WS2 leads to the formation of small nm-sized metal islands (Volmer-Weber growth mode).

The experiments are carried out under UHV conditions. A homebuilt VT-UHV-STM is used to study the nucleation and growth of metal islands (e.g. Au, Ag) on WSe2 or WS2. Our results show that the measured island density does not clearly fit the standard nucleation theory, thus we assume that heterogeneous nucleation take place on these No-dqidealNo-dq surfaces. With our setup we are able to evaporate the metal directly under the STM tip. By taking STM pictures before and after evaporation it is possible to investigate and identify the surface defects which influence the nucleation process. Indeed we found that electronic defects like surface dopant sites determine the nucleation process and consequently the island density, although they do not appear as topographic defects. By further evaporation we also study the growth of individual islands whereby we found a growth stop in height.

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