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Title: A combined STM and SPA-LEED study of the “explosive” nucleation and collective diffusion in Pb/Si(111)

A novel type of very fast nucleation was recently found in Pb/Si(111) with 4- to 7-layer high islands becoming crystalline in an “explosive” way, when the Pb deposited amount in the wetting layer is compressed to θc ~ 1.22 ML, well above the metallic Pb(111) density. This “explosive” nucleation is very different from classical nucleation when island growth is more gradual and islands grow in size by single adatom aggregation [8]. In order to identify the key parameters that control the nucleation we used scanning tunneling microscopy (STM) and spot profile analysis low energy electron diffraction (SPA-LEED). It was found that the number and duration of steps in iterative deposition used to approach θc and the flux rate have dramatic effects on the crystallization process. Larger depositions over shorter times induce greater spatial coverage fluctuations, so local areas can reach the critical coverage θc easier. This can trigger the collective motion of the wetting layer from far away to build the Pb islands “explosively”. Here, the SPA-LEED experiments show that even low flux experiments in iterative deposition experiments can trigger transfer of material to the superstable 7-layer islands, as seen from the stronger satellite rings close to the (00) spot.
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  1. Ames Lab. and Iowa State Univ., Ames, IA (United States)
  2. Univ. of Duisburg-Essen, Duisburg (Germany)
Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 0039-6028; PII: S003960281500237X
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Surface Science
Additional Journal Information:
Journal Volume: 646; Journal Issue: C; Journal ID: ISSN 0039-6028
Research Org:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org:
Country of Publication:
United States
36 MATERIALS SCIENCE epitaxial growth; nucleation; surface diffusion; STM. SPALEED; Pb/Si(111)