The Pb diffused in a Pb/Cu(111) surface alloy predominantly by exchange with surface vacancies and, much less frequently, by exchange with thermal Cu adatoms. Because the

infrequent adatom exchanges transport Pb atoms much farther, both processes affected observations of Pb transport in the Pb/Cu(111) surface alloy.

Vacancy-Mediated and Exchange Diffusion in a Pb/Cu(111) Surface Alloy - Concurrent Diffusion on Two Length Scales. M.L.Anderson, M.J.D'Amato, P.J.Feibelman, B.S.Swartzentruber: Physical Review Letters, 2003, 90[12], 126102 (4pp)