Session E6 - Nanoparticles and Their Assemblies I.
MIXED session, Tuesday morning, March 19
Room 260, America's Center

[E6.09] Determining the Atomic Structure and Orienatation of Nanometer-size Supported Clusters

D. Lovall, R.P. Andres, R. Reifenberger (Purdue University)

Techniques have been developed to produce and deposit nanometer-size Au clusters on the apex of a sharp tungsten tip that allow imaging of the surface atoms on the cluster using field-ion micrsocopy (FIM). We report on the comparison between our initial FIM images and computer simulations of the images using atomic models for the individual clusters. This technique is capable of providing an experimental check on calculations of the structure and atomic arrangement of atoms in supported nanometer-size clusters. Preliminary results demonstrate a promising future for this approach. Simulations of FIM micrographs from a Au cluster have been completed and clearly show 2-fold, 3-fold, and 5-fold symmetry, depending on the cluster orientation. Comparisons of simulated FIM images from a 309 atom icosahedral Au cluster to experimental FIM images from a \sim 2 nm diameter unannealed Au cluster show striking similarities and permit a determination of the orientation and structure of an individual supported cluster.