Nothing moves a surface: vacancy mediated surface diffusion

Abstract

We report scanning tunneling microscopy observations, which imply that all atoms in a close-packed copper surface move frequently, even at room temperature. Using a low density of embedded indium `tracer' atoms, we visualize the diffusive motion of surface atoms. Surprisingly, the indium atoms seem to make concerted, long jumps. Responsible for this motion is an ultra-low density of surface vacancies, diffusing rapidly within the surface. This interpretation is supported by a detailed analysis of the displacement distribution of the indium atoms, which reveals a shape characteristic for the vacancy mediated diffusion mechanism that we propose.

4 pages; for associated movie, see http://www-lion.leidenuniv.nl/sections/cm/groups/interface/projects/thermo

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• Tracer diffusion in crowded narrow channels. Topical review
• Vacancy diffusion in the Cu(001) surface I: An STM study
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• Vacancy diffusion in the Cu(001) surface II: Random walk theory
• First exit times and residence times for discrete random walks on finite lattices
• Growth of germanium-silver surface alloys followed by in situ scanning tunneling microscopy: Absence of germanene formation
• Distance scaling and polarization of electric-field noise in a surface ion trap
• Relaxation of Terrace-width Distributions: Physical Information from Fokker-Planck Time
• The Atomic Slide Puzzle: Self-Diffusion of an Impure Atom
• Directed long-range transport of a nearly pure component atom clusters by the electromigration of a binary surface alloy
• Vacancy-mediated suppression of phase separation in a model two-dimensional surface alloy by the difference of the atomic jump rates