An In/Cu surface alloy was used to study the dynamics of surface vacancies on the Cu(001) surface. Individual In atoms that were embedded within the first layer of the crystal, were used as probes to detect the rapid diffusion of surface vacancies. Scanning tunnelling microscopic measurements showed that these In atoms made multi-lattice-spacing jumps, separated by long time intervals. Temperature dependent waiting-time distributions showed that the creation and diffusion of thermal vacancies formed an Arrhenius type process with individual long jumps being caused by one vacancy only. The length of the long jumps was shown to depend on the specific location of the In atom and was directly related to the lifetime of vacancies at these sites on the surface. This observation was used to expose the role of step edges as emitting and absorbing boundaries for vacancies.

Vacancy Diffusion in the Cu(001) Surface - an STM Study. R.van Gastel, E.Somfai, S.B.van Albada, W.van Saarloos, J.W.M.Frenken: Surface Science, 2002, 521[1-2], 10-25