Bilayer-ring second-layer nucleation morphology in Pb/Si(111)-7x7

TitleBilayer-ring second-layer nucleation morphology in Pb/Si(111)-7x7
Publication TypeJournal Article
Year of Publication2007
AuthorsKuntova Z, Hupalo M, Chvoj Z, Tringides MC
Journal TitlePhysical Review B
Volume75
Pages205436
Date PublishedMay
Type of ArticleArticle
ISBN Number1098-0121
Accession NumberISI:000246890900137
Keywordsfilms, growth, transition
Abstract

The formation of the uniform height Pb islands on Si(111) is unusually fast and it is important to understand the driving forces responsible for it. The growth to bigger heights proceeds by bilayer rings nucleating first at the island perimeter, which spread out toward the island center. The rings have sharp growth fronts and it is challenging to explain this unusual morphology with the same set of barriers for island heights of the same stability, since nucleation is restricted to 2 layers. With Monte Carlo simulations, this nucleation morphology is reproduced and the corresponding potential-energy surface (PES) identified. The key barriers of the PES are very fast terrace diffusion (with barrier less than 50 meV), highly anisotropic diffusion (i.e., the azimuthal diffusion within a one-lattice-constant ring is 1000 times faster than radial diffusion toward the island center), and interlayer diffusion barriers for stable versus unstable islands differing by 0.11 eV (for diffusion from the island top back to the wetting layer).

DOI10.1103/PhysRevB.75.205436
Alternate JournalPhys. Rev. B