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Superdiffusive motion of the Pb wetting layer on the Si(111) surface
K L Man1, M C Tringides, M M T Loy
1Department of Physics, Hong Kong University of Science and Technology, Kowloon, Hong Kong, China.
Physical Review Letters
|February 5, 2013
Summary
Mass transport on silicon surfaces defies classical diffusion. Unusual collective superdiffusive mechanisms may explain the observed Pb wetting layer behavior on Si(111).
Area of Science:
- Surface Science
- Materials Science
- Condensed Matter Physics
Background:
- Understanding mass transport is crucial for thin film growth and surface phenomena.
- Lead (Pb) wetting layers on silicon (Si) surfaces are model systems for studying surface diffusion.
Purpose of the Study:
- To investigate the mass transport mechanisms in the Pb wetting layer on the Si(111) surface.
- To analyze the evolution of nonequilibrium coverage profiles and compare them to classical diffusion models.
Main Methods:
- Utilizing low energy electron microscopy (LEEM) to observe surface morphology.
- Employing micro low energy electron diffraction (µLEED) to analyze surface structure and ordering.
- Creating and monitoring nonequilibrium coverage step profiles.
Main Results:
- Observed equilibration of coverage step profiles through mass exchange between oppositely directed, self-moving coverage gradients.
- The initial profile bifurcation and subsequent evolution did not align with classical diffusion predictions.
- The observed phenomena suggest a deviation from standard diffusion behavior.
Conclusions:
- The mass transport in the Pb wetting layer on Si(111) exhibits characteristics inconsistent with classical diffusion.
- The findings point towards an unusual coverage dependence of diffusion or a collective superdiffusive mechanism.
