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

Journal Article · Thu Aug 20 00:00:00 EDT 2015 · Surface Science

DOI:https://doi.org/10.1016/j.susc.2015.08.017· OSTI ID:1278827

Hattab, H. ^[1]; Hupalo, M. ^[1]; Hershberger, M. T. ^[1]; Horn von Hoegen, M. ^[2]; Tringides, M. C. ^[1]

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1. Ames Lab. and Iowa State Univ., Ames, IA (United States)
2. Univ. of Duisburg-Essen, Duisburg (Germany)

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 θ_c ~ 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 θ_c 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.

• Research Organization: Ames Lab., Ames, IA (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC02-07CH11358
• OSTI ID: 1278827
• Report Number(s): IS-J-9018; PII: S003960281500237X
• Journal Information: Surface Science, Vol. 646, Issue C; ISSN 0039-6028
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
epitaxial growth
nucleation
surface diffusion
STM. SPALEED
Pb/Si(111)