Journal
SURFACE SCIENCE
Volume 646, Issue -, Pages 50-55Publisher
ELSEVIER
DOI: 10.1016/j.susc.2015.08.017
Keywords
Epitaxial growth; Nucleation; Surface diffusion; STM, SPALEED; Pb/Si(111)
Categories
Funding
- Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division of the U.S. Department of Energy (USDOE) with the U.S. Department of Energy [DE-AC02-07CH11358]
- Leopoldina Fellowship Program LPDS of the German National Academy of Sciences
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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 theta(c) similar to 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 theta(c), 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 theta(c), easier. This can trigger the collective motion of the wetting layer from far away to build the Pb islands explosively. 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. (C) 2015 Elsevier B.V. All rights reserved.
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