Novel mechanism for diffusion of one-dimensional clusters: Pt/Pt(110)-(1x2)

We report on a novel diffusion mechanism for one-dimensional platinum clust ers on the anisotropic Pt(110)-(1 X 2) surface. The mechanism, which is rev ealed from atom-resolved, time-lapsed scanning tunneling microscopy movies, entails that the end atom of a cluster is promoted up to the next layer, m igrates over the cluster, and drops down again, resulting in a cluster- dis placement by one lattice spacing. The activation barriers for the atom to a scend and descend the cluster edges are estimated to be 0.91 and 0.70 eV, r espectively. The reported observations have already inspired theoretical ca lculations. [S0031-9007(99)08442-2].