The migration of individual Pt adatoms, and clusters of 2 to 6 atom, on the (100) surface of Rh was investigated by means of field ion microscopy. The mode of diffusion of adatoms and clusters was deduced to be that of conventional site-to-site hopping. Single adatoms and dimers migrated at temperatures ranging from 314 to 346K; with an activation energy of 0.92eV and a pre-exponential factor of 0.002cm2/s. Trimers and tetramers, which were more stable as 1-dimensional chains than as 2-dimensional islands (as well as pentamers, which were equally stable as chains or islands), all diffused with the same activation energy of 1.03eV. Hexamers, which were more stable as islands than as chains, migrated with the somewhat higher activation energy of 1.16eV. The relative stabilities of chains, as compared with islands, indicated the occurrence of long-range adatom-adatom interactions in the clusters.

G.L.Kellogg: Applied Surface Science, 1993, 67, 134-41