Adatom capture by arrays of two-dimensional Ag islands on Ag(100)

We examine the capture of diffusing Ag adatoms by arrays of two-dimensional Ag islands subsequent to deposition on Ag(100) at room temperature. This is achieved by a combination of scanning tunneling microscopy experiments, kinetic Monte Carlo simulations, and diffusion equation analyses. The dependence of the capture rates on Ag-island size is shown to reflect larger island-free regions surrounding the larger islands, i.e., a strong correlation between island sizes and separations. This feature, and the influence of the local environment of the islands on capture, are elucidated by introducing suitable tessellations of the surface into “capture zones” for each island. We show that a Voronoi-type tessellation based on the distance from the island edges accurately reflects adatom capture. However, a tessellation exactly describing adatom capture is only obtained from a solution of the steady-state equation describing adatom deposition, diffusion, and capture by an array of islands distributed as in experiment. The stochastic nature of adatom capture is also quantified by analysis of the dependence on the deposition location of the probability for diffusing adatoms to be captured by a specific island. The experimental island size dependence of adatom capture is found to be entirely consistent with that obtained from a “canonical” model for the irreversible nucleation and growth of square islands. Disciplines Mathematics | Physical Chemistry Comments This article is from Physical Review B 59, no. 4 (1999): 3125–3134, doi:10.1103/PhysRevB.59.3125. This article is available at Iowa State University Digital Repository: http://lib.dr.iastate.edu/chem_pubs/69 Adatom capture by arrays of two-dimensional Ag islands on Ag„100... M. C. Bartelt Sandia National Laboratories, Livermore, California 94550 C. R. Stoldt, C. J. Jenks, and P. A. Thiel Department of Chemistry and Ames Laboratory, Iowa State University, Ames, Iowa 50011 J. W. Evans Department of Mathematics and Ames Laboratory, Iowa State University, Ames, Iowa 50011 ~Received 12 August 1998! We examine the capture of diffusing Ag adatoms by arrays of two-dimensional Ag islands subsequent to deposition on Ag~100! at room temperature. This is achieved by a combination of scanning tunneling microscopy experiments, kinetic Monte Carlo simulations, and diffusion equation analyses. The dependence of the capture rates on Ag-island size is shown to reflect larger island-free regions surrounding the larger islands, i.e., a strong correlation between island sizes and separations. This feature, and the influence of the local environment of the islands on capture, are elucidated by introducing suitable tessellations of the surface into ‘‘capture zones’’ for each island. We show that a Voronoi-type tessellation based on the distance from the island edges accurately reflects adatom capture. However, a tessellation exactly describing adatom capture is only obtained from a solution of the steady-state equation describing adatom deposition, diffusion, and capture by an array of islands distributed as in experiment. The stochastic nature of adatom capture is also quantified by analysis of the dependence on the deposition location of the probability for diffusing adatoms to be captured by a specific island. The experimental island size dependence of adatom capture is found to be entirely consistent with that obtained from a ‘‘canonical’’ model for the irreversible nucleation and growth of square islands. @S0163-1829~99!14003-7#