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Nonclassical "explosive" nucleation in Pb/Si(111) at low temperatures
M T Hershberger1, M Hupalo2, P A Thiel3
1Ames Laboratory-U.S. Department of Energy, Iowa State University, Ames, Iowa 50011, USA and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA.
Physical Review Letters
|December 20, 2014
Summary
Nucleation in Pb/Si(111) occurs explosively, not gradually. This new mechanism involves coherent motion of the wetting layer over mesoscopic distances, challenging classical nucleation theory.
Area of Science:
- Surface science
- Condensed matter physics
- Materials science
Background:
- Classical nucleation theory describes island formation via gradual adatom aggregation.
- Previous studies focused on gradual adatom diffusion and aggregation for nucleation.
Purpose of the Study:
- To investigate an alternative nucleation mechanism observed in Pb/Si(111) experiments.
- To challenge and expand upon classical nucleation theory.
Main Methods:
- Low-temperature experimental observations of Pb/Si(111).
- Analysis of island formation dynamics and growth rates.
- Investigation of adatom behavior and wetting layer properties.
Main Results:
- Observed "explosive" nucleation of perfect crystalline islands.
- Identified a critical coverage (Θ_{c}=1.22 ML) for this explosive event.
- Noted high island growth rates and directional correlations between islands.
- Evidence of coherent wetting layer motion over mesoscopic distances.
Conclusions:
- The observed nucleation is driven by a highly coherent motion of the wetting layer.
- This suggests a departure from classical nucleation models based on random diffusion.
- The findings offer new insights into non-classical nucleation phenomena.
