Kink Diffusion at a Peninsula Formed by the Reaction of Br₂ with Cu(100)

After saturation of a chemisorbed layer, Br₂ reacts with Cu to form CuBr. Copper atoms for the reaction are preferentially removed from step edges. The reactivity of the steps is anisotropic resulting in peninsulas such as the one shown above. The corrugation in the images is due to adsorbed Br atoms. Notice there are no kinks on the steps on either the upper or right side of the peninsula. The movie shows that changes in the step shape only occurs on the left side and is associated with motion of the kinks. Thus, the lowest energy path for motion of the step edges is kink diffusion. Also note that the diffusion in this case involves the coordinated motion of the adsorbed Br atoms and the substrate Cu atoms to which they are bound.