The behavior of Pd adatoms on the (110) surface of Ta was investigated by using field ion microscopy. The results indicated that the Pd atoms became mobile at 180K, and diffused with an activation energy of 0.49eV. The structure of small Pd clusters on the plane depended upon the number of Pd adatoms which was present on the plane. If less than 9 were deposited, the stable configuration was a linear chain which was oriented along a close-packed direction of the substrate. Two-dimensional island clusters containing less than 9 atoms were metastable. The stable configuration for more than 9 atoms was a two-dimensional island cluster, while the linear chain was metastable. Two-dimensional Pd clusters migrated as a unit at temperatures of between about 250 and 325K. At temperatures greater than about 350K, the clusters rapidly disappeared from the plane.

P.R.Schwoebel, G.L.Kellogg: Physical Review B, 1988, 38[8], 5326-31