Monolayer-deep vacancy islands were created, using a scanning tunnelling microscope, on (111) Cu surfaces which were covered with sub-monolayer amounts of Co. Their motion was then monitored in real time at room temperature. Quantitative evaluation of their random walk permitted their diffusion coefficient to be evaluated.

J.De la Figuera, J.E.Prieto, C.Ocal, R.Miranda: Solid State Communications, 1994, 89[9], 815-8