Surface diffusion of Pb and Bi over Cu(100) surfaces was studied by scanning Auger microscopy techniques. The diffusion profiles of Pb and Bi were found to be quite different. The results showed that three major factors controlled the shapes of the surface diffusion profiles: (a) First order phase transitions, which lead to phase coexistence over specified coverage ranges, tend to produce abrupt changes in coverage versus distance profiles; (b) profiles could be affected by the existence of significant differences in the diffusion coefficients of the various phases present, and by the possibility (c) of important changes in diffusivity within a given phase, as a function of coverage, due to interactions between the diffusing atoms. In addition, it was shown that the strong connection between diffusion profile shapes and the 2D phase diagram permitted certain features of the 2D phase diagram to be determined from diffusion profiles.

Impact of Surface Phase Transitions and Structure on Surface Diffusion Profiles of Pb and Bi over Cu(100). J.P.Monchoux, D.Chatain, P.Wynblatt: Surface Science, 2006, 600[6], 1265-76