Perturbed angular correlation experiments, using soft-landed 111Ag probe atoms on a Ag(100) surface, permitted the monitoring of the self-diffusion of Ag on the surface. Three different sites were observed as a function of substrate temperature. These were the adatomic terrace site, at temperatures of 80 to 150K, the adatomic step-site at temperatures of between 130 and 180K, and the substitutional terrace site at temperatures above 150K; where adatoms were still present on the surface The data could be explained only by assuming that the hopping diffusion mechanism was active at low temperatures, while the exchange mechanism explained the substitutional terrace site at 150K. In the case of the exchange mechanism, one movement was enough to occupy a substitutional terrace site. This gave an activation energy of 0.46eV. This value was about 0.1eV higher than the activation energy for hopping.

Direct Observation of the Self-Diffusion Mechanism on the Ag(100) Surface. M.F.Rosu, C.R.Laurens, A.Falepin, M.A.James, M.H.Langelaar, F.Pleiter, O.C.Rogojanu, L.Niesen: Physical Review Letters, 1998, 81[21], 4680-3