Field-ion microscopy of supported nanometer size gold clusters and carbon nanotubes
Abstract
The structure and stability of nanometer-size Au clusters is investigated using field-ion microscopy. Molecular dynamics simulations of Au clusters in the 2-4 nm size range predict a truncated octahedral equilibrium structure. By comparing experimental field-ion microscope (FIM) images of Au clusters placed on the apex of a FIM tip to simulated images, a determination of the structure and orientation of clusters supported on a variety of substrates (W, Pt, Pt/Ir) is made. We find that clusters annealed in the gas phase attain a truncated octahedral shape. Unannealed clusters are found to exist as multiply twinned particles. The electrical arid structural properties of carbon nanotubes are investigated using field emission and field-ion microscopy. Measurements of the total energy distribution (TED) of field emitted electrons from a bundle of single walled nanotubes show that the bundle has metallic electrical properties. A determination of the work function of this bundle is made. Field-ion images of the same bundle are compared to simulated images from bundles of nanotubes with different end forms.
Degree
Ph.D.
Advisors
Reifenberger, Purdue University.
Subject Area
Condensation
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