Scanning tunneling microscopy and low-energy electron microscopy were used to measure the thermal decay of 2-dimensional Cu, Pb-overlayer and Pb–Cu alloy islands on Pb–Cu(111) surface alloys. Decay rates which spanned 6 to 7 orders of magnitude were accessible by applying the 2 techniques to the same system. It was found that Cu adatom diffusion across the surface alloy was rate-limiting for the decay of Pb and Pb–Cu islands on the surface alloy. This rate decreased monotonically with increasing Pb concentration in the alloy, and the decrease was attributed to repulsive interactions between Cu adatoms and embedded Pb atoms in the surface alloy. The temperature dependences of the island decay rates were consistent with first-principles calculations of Cu binding and of diffusion energies related to the so-called site-blocking effect.

The Effect of Embedded Pb on Cu Diffusion on Pb/Cu(111) Surface Alloys. M.L.Anderson, N.C.Bartelt, P.J.Feibelman, B.S.Swartzentruber, G.L.Kellogg: Surface Science, 2006, 600[9], 1901-8