SELF-DIFFUSION ON THE RECONSTRUCTED AND NONRECONSTRUCTED IR(110) SURFACES

On the (1 x 1) Ir(110) surface the diffusion of single Ir adatoms is two dimensional; i.e., an adatom can diffuse along the [11BAR0] surface channel by atomic hopping as well as across the channel by atomic replacement. The energy needed for an Ir adatom to hop along the channel is 0.80 +/- 0.04 eV, or 0.09 eV larger than needed to replace a lattice atom in the cross-channel jump. In contrast, Ir adatom diffusion on the (1 x 2)-reconstructed surface, with double-space [11BAR0] channels, is one dimensional; i.e., an adatom can only hop along these channels. The activation energy, 0.86 +/- 0.03 eV, is higher than that for either cross-channel or along-the-channel diffusion on the nonreconstructed surface.