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Surface diffusion experiments with STM: equilibrium correlations and non-equilibrium low temperature growth

TitleSurface diffusion experiments with STM: equilibrium correlations and non-equilibrium low temperature growth
Publication TypeJournal Article
Year of Publication2010
AuthorsTringides MC, Hupalo M
Journal TitleJournal of Physics-Condensed Matter
Volume22
Pages264002
Date Published07/07
ISBN Number0953-8984
Accession NumberISI:000278802000008
Keywordscurrent fluctuations, evolution, films, ISLANDS, nucleation, overlayers, pb, UNIFORM
Abstract

Measurements of surface diffusion depend on the state of the system whether the state is equilibrium versus non-equilibrium. Equilibrium experiments carried out in 2-d overlayers measure the collective diffusion coefficient D-c and can test theoretical predictions in two-dimensional statistical mechanics. Growth experiments typically carried out at low temperatures and/or high flux rates probe systems under non-equilibrium conditions where novel diffusion mechanisms can potentially exist. The use of STM to study both types of measurements is discussed. Dc can be measured from the autocorrelation of time-dependent tunneling current fluctuations generated by atom motion in and out of the tunneling area. Controlled experiments as function of temperature, coverage and tip-surface separation confirm that the signal is diffusive. For growth experiments the unusually uniform height island (for Pb/Si(111) In/Si(111)) has revealed a novel and intriguing type of diffusion at low temperatures that accounts for the high degree of the self organization. By monitoring the evolution of the stable islands out of a mixture of stable and unstable islands the unusual role of the wetting layer surrounding the growing islands is revealed.
URL<Go to ISI>://000278802000008
DOI10.1088/0953-8984/22/26/264002