By means of field-ion microscopy it was found that, on the 1 x 1 Ir(110) surface, the diffusion of single Ir adatoms was 2-dimensional. Thus, the adatom could diffuse along the [1¯10] surface channel by atomic hopping, as well as across the channel by atomic replacement. The activation energy which was required for an adatom to hop along the channel was 0.80eV:

cross-channel: D (cm2/s) = 0.06 exp[-0.71(eV)/kT]

along-channel: D (cm2/s) = 0.004 exp[-0.80(eV)/kT]

This value was 0.09eV larger than the energy which was required to replace a lattice atom in the cross-channel jump. On the other hand, adatom diffusion on the 1 x 2 reconstructed surface, with doubly-spaced [1¯10] channels, was 1-dimensional and an adatom could only hop along these channels:

D (cm2/s) = 0.0012 exp[-0.86(eV)/kT]

The activation energy of 0.86eV was higher than that for either cross-channel or along-channel diffusion on the non-reconstructed surface.

C.Chen, T.T.Tsong: Physical Review Letters, 1991, 66[12], 1610-3

Figure 15

Diffusivity of 7-Atom Ir Groups on the (111) Ir Surface