AVS 49th International Symposium
    Surface Science Friday Sessions
       Session SS-FrM

Paper SS-FrM10
Metastable Nanopattern Formation during Pb/Cu(111) Self-Assembly

Friday, November 8, 2002, 11:20 am, Room C-110

Session: Self-Assembly at Surfaces
Presenter: G.L. Kellogg, Sandia National Laboratories, Albuquerque
Authors: R. van Gastel, Sandia National Laboratories, Albuquerque
R. Plass, Sandia National Laboratories, Albuquerque
N.C. Bartelt, Sandia National Laboratories, Livermore
G.L. Kellogg, Sandia National Laboratories, Albuquerque
Correspondent: Click to Email
Competing inter-atomic interactions on surfaces can lead to the spontaneous formation of ordered 2-D domain patterns in widely varying systems. The potential use of such patterns as templates for the fabrication of nanostuctures has fostered considerable interest in the underlying self-assembly process. Recently, it has been discovered that two phases of Pb on Cu(111) (a surface alloy and a Pb overlayer) self-assemble into nanoscale domain patters.@footnote 1@ As the Pb coverage increases, the equilibrium patterns progress from islands of the overlayer (droplets) to stripes to islands of the alloy (inverted droplets). These equilibrium patterns are not the only patterns that can be constructed, however. Here, we use low energy electron microscopy to investigate metastable patterns that can be created by varying the temperature and deposition sequence. These include a stripe phase formed at low Pb coverages, and metastable droplet and inverted droplet phases, in which the island sizes are larger than those of the equilibrium structures. Both the droplet and inverted droplet metastable structures can develop into "froth" patterns -- the 2-D analog of soap bubbles. These patterns evolve in a deterministic manner. If the droplet phase from which a froth phase is created is ordered, a stable array of ordered hexagonal domains results. If the initial droplet phase is not ordered, the froth phase coarsens by a well-defined set of rules.@footnote 2@ Thus, Pb on Cu(111) provides a model system both to explore the type of metastable patterns that can be formed for nano-template applications and to determine the laws that govern the formation, evolution and stability of nanometer-scale, 2-D patterns. Work supported by the U. S. DOE under Contract DE-AC04-94AL85000. @FootnoteText@ @footnote 1@ R. Plass, J. A. Last, N. C. Bartelt, and G. L. Kellogg, Nature 412, 875 (2001)@footnote 2@ D. Weaire and N. Rivier, Contemp. Phys. 25, 59 (1984)