Nucleation on a stepped surface with an Ehrlich-Schwobel barrier

TitleNucleation on a stepped surface with an Ehrlich-Schwobel barrier
Publication TypeJournal Article
Year of Publication2013
AuthorsChromcova Z, Tringides MC, Chvoj Z
Journal TitleJournal of Physics-Condensed Matter
Date Published07
Type of ArticleArticle
ISBN Number0953-8984
Accession NumberWOS:000320329400004
KeywordsEDGE, epitaxy, flow growth, mediate, si, sn layer, transition

During deposition on a stepped surface the growth mode depends on the conditions such as temperature T, deposition rate F and width of the terraces w. In this work we studied the influence of all the above mentioned characteristics using the kinetic Monte Carlo (kMC) technique. We concentrated on the conditions on the terrace at the moment of the first nucleation. The critical density of monomers for nucleation eta(m) decreases with the width of the terrace and the nucleation starts at surprisingly low densities of monomers. We tested several definitions of the critical width for nucleation w(c) used in various articles in the past and we compared our results with results of the analytical steady-state mean-field model (Ranguelov and Altman 2007 Phys. Rev. B 75 245419). To check how the simplified assumption about the steady-state regime during deposition influences the resulting dependence of w(c) similar or equal to (D/F)(kappa), we set and also solved a time-dependent analytical model. This analytical model as well as kMC predict that w(c) similar or equal to (D/F)(1/5). kMC simulation also shows that the Ehrlich-Schwobel barrier has only limited influence on the nucleation on the stepped surface at conditions close to the nucleation regime. For all widths of terraces there is a critical value of the Ehrlich-Schwobel barrier Delta E-ES(c)/k(B)T similar to 7.3 (Delta E-ES(c) similar to 0.11 eV at T = 175 K), and only below this critical value does the Ehrlich-Schwobel barrier affect the final value of the density of nuclei. The results of the kMC are summarized in a semi-empirical analytical formula which describes the dependence of the step-flow growth and nucleation on the terrace width w, diffusion coefficient D and deposition rate F. In our simulations we tested two models of the stepped surface with different thicknesses of the step, both with an Ehrlich-Schwobel barrier on the edge of the terrace.

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