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Vacancy-mediated and exchange diffusion in a Pb/Cu(111) surface alloy: concurrent diffusion on two length scales
M L Anderson1, M J D'Amato, P J Feibelman
1Sandia National Laboratories, Albuquerque, New Mexico 87185, USA.
Physical Review Letters
|April 12, 2003
Summary
Lead (Pb) atoms on a copper (Cu) surface alloy primarily move by swapping with vacancies. Less frequent exchanges with copper adatoms significantly increase the distance lead atoms travel, impacting transport observations.
Area of Science:
- Materials Science
- Surface Science
- Physical Chemistry
Background:
- Understanding surface alloy dynamics is crucial for catalysis and electronics.
- Lead (Pb) diffusion on copper (Cu) surfaces presents unique challenges due to differing atomic properties.
Purpose of the Study:
- To elucidate the primary mechanisms governing lead diffusion on a Pb/Cu(111) surface alloy.
- To differentiate the contributions of various diffusion pathways to overall lead transport.
Main Methods:
- Utilizing surface science techniques to observe and analyze atomic interactions.
- Investigating diffusion through vacancy exchange and adatom-mediated transport.
Main Results:
- Lead diffusion predominantly occurs via exchange with surface vacancies.
- Less frequent exchange with thermal copper adatoms results in significantly longer-range transport of lead atoms.
- Both diffusion mechanisms critically influence the observed lead transport characteristics.
Conclusions:
- The interplay between vacancy-mediated and adatom-mediated diffusion dictates lead atom mobility on the Cu(111) surface alloy.
- Accurate modeling of surface alloy behavior requires consideration of multiple, distinct diffusion pathways.