Photo-emission observations of the temporal evolution of the Pd/Ag(100) system at various temperatures permitted an estimation to be made of the diffusion barriers that were involved in surface alloy formation. It was found that adatom migration occurred in distinct steps. The first step involved an exchange mechanism that occurred at about 135K, with an activation energy of 0.43eV. On the other hand, migration from a surface layer to a sub-surface layer was observed at temperatures above 360K, with an activation energy of 1.12eV.

F.Patthey, C.Massobrio, W.D.Schneider: Physical Review B, 1996, 53[19], 13146-9