The diffusion of individual Pt adatoms on the (100), (110), (311) and (111) surfaces was investigated by means of field ion microscopy. On the (100) and (110) surfaces, Pt adatoms replaced Ni substrate atoms at temperatures below the onset of hopping displacement. The minimum temperatures which were required for replacement were 250 and 105K for the (100) and (110) surfaces, respectively. On the (311) and (111) surfaces, Pt adatoms migrated via normal site-to-site hopping. The activation energies for diffusion on the (100), (110) and (311) surfaces were deduced to be equal to 0.69, 0.28 and 0.38eV, respectively.

G.L.Kellogg: Surface Science, 1992, 266, 18-23