Modelling of diffusion from equilibrium diffraction fluctuations in ordered phases

TitleModelling of diffusion from equilibrium diffraction fluctuations in ordered phases
Publication TypeJournal Article
Year of Publication2008
AuthorsArapaki E, Argyrakis P, Tringides MC
Journal TitleSurface Science
Volume602
Pages2162-2169
Date PublishedJul
Type of ArticleArticle
ISBN Number0039-6028
Accession NumberISI:000257837500008
KeywordsADSORBATE ADSORBATE INTERACTIONS, ATTRACTIVE, collective diffusion, diffusion, fluctuations, interactions, lattice gas models, particle, phase, REPULSIVE INTERACTIONS, surface diffusion, SURFACE-DIFFUSION, TRANSITIONS
Abstract

Measurements of the collective diffusion coefficient D-c at equilibrium are difficult because they are based on monitoring low amplitude concentration fluctuations generated spontaneously, that are difficult to measure experimentally. A new experimental method has been recently used to measure time-dependent correlation functions from the diffraction intensity fluctuations and was applied to measure thermal step fluctuations. The method has not been applied yet to measure superstructure intensity fluctuations in surface overlayers and to extract D-c. With Monte Carlo simulations we study equilibrium fluctuations in lsing lattice gas models with nearest neighbour attractive and repulsive interactions. The extracted diffusion coefficients are compared to the ones obtained from equilibrium methods. The new results are in good agreement with the results from the other methods, i.e., D-c decreases monotonically with coverage 0 for attractive interactions and increases monotonically with theta for repulsive interactions. Even the absolute value of D-c agrees well with the results obtained with the probe area method. These results confirm that this diffraction based method is a novel, reliable way to measure D-c especially within the ordered region of the phase diagram when the superstructure spot has large intensity. (c) 2008 Elsevier B.V. All rights reserved.

DOI10.1016/j.susc.2008.04.008
Alternate JournalSurf. Sci.