The use of field ion microscopic techniques showed that individual Rh adatoms on the (100) surface were trapped at the 4 lattice sites which were next to an Ir substitutional atom which was embedded in the surface. It was found that the activation barrier to the escape of a Rh atom from the impurity trap was 0.95eV. This was considerably higher than the self-diffusion barrier (0.83eV) for the defect-free surface. The barrier to movement between the 4 equivalent trap sites was 0.76eV. It was concluded that increased binding, together with a higher Rh desorption field at the trap sites, implied a stronger Ir-Rh bond than Rh-Rh bond.

G.L.Kellogg: Physical Review Letters, 1994, 72[11], 1662-5

Table 249

Activation Energies for Pt Diffusing on Rh Surfaces