AVS 46th International Symposium
    Surface Science Division Wednesday Sessions
       Session SS3+NS-WeA

Paper SS3+NS-WeA2
The Phase Diagram of a Self-Organizing Nano-Array

Wednesday, October 27, 1999, 2:20 pm, Room 604

Session: Islands, Clusters, and Steps
Presenter: K. Pohl, Sandia National Laboratories
Authors: K. Pohl, Sandia National Laboratories
J. de la Figuera, Sandia National Laboratories
M.C. Bartelt, Sandia National Laboratories
N.C. Bartelt, Sandia National Laboratories
J. Hrbek, Brookhaven National Laboratory
R.Q. Hwang, Sandia National Laboratories
Correspondent: Click to Email
Recent experiments show that in a submonolayer silver film on Ru(0001), a perfectly ordered array of nanometer-sized vacancy islands forms upon exposure to sulfur. By measuring the thermal vibrations of this equilibrium structure the forces responsible for the observed self-organization were identified and the elastic constants of the lattice derived.@footnote 1@ In order to develop a better understanding of the formation and ordering processes of this structure, we have explored the complete phase diagram of the vacancy island lattice. Via scanning tunneling microscopy we follow in real time the assembly of the hole lattice at different temperatures and S-Ag coverages. We find the hole lattice to be very robust against annealing cycles to 500 K. The final periodicity of the vacancy island lattice seems to be independent of the periodicity of the initial dislocation network in the strained silver film. This network only determines the initial etching sites for the S adatoms. The periodicity of the dislocation network in the clean Ag film depends on the Ag coverage. Beyond a threshold S-coverage, the array undergoes a phase transition to a periodic array of stripes. We will present a detailed study of the stability of these various novel equilibrium phases and identify the driving forces behind their formation. This work is supported by the Office of Basic Energy Sciences Division of Materials Sciences of the U.S. DOE (DE-AC04-94AL85000). @FootnoteText@ @footnote 1@K. Pohl et al., Nature 397, 238 (1999)