Impurity Effect on Surface Diffusion: CO/S/Ni(110)

Macroscopic CO diffusion on Ni(110) was found to be greatly impeded by surface contamination of just a few percent of a sulfur monolayer. The effect became even much more pronounced if the sample was annealed at high temperatures. The results can be understood from the consideration that S-covered steps can effectively block CO diffusion with a much higher energy barrier.