SELF-DIFFUSION ON RECONSTRUCTED AND NONRECONSTRUCTED-LR SURFACES

Using the field ion microscope, we have studied random walk diffusion of single Ir atoms and small Ir atomic clusters on Ir surfaces. On the (1 X 1) Ir {001} surface, diffusion of Ir adatoms occurs by an atomic replacement mechanism along the [001] directions. On the (1 X 1) Ir {110} surface, self-diffusion occurs by atomic hopping along the [110] directions and by atomic replacement along the [001] directions. On the (1 X 2) reconstructed Ir {110} surface, self-diffusion occurs only by atomic hopping along the doubly spaced [110BAR] surface channels. Within the experimental accuracy, the pre-exponential factors are all in the 10(-3) cm2/s range. Energies needed for these atomic replacements and the barrier heights for these atomic hoppings are also derived. Diffusion of diatomic clusters on the (1 X 1) Ir {110} surfaces has also been studied.