A scanning tunneling microscopy study of metal films and supported gold particles
Thomas, Patrick Allen
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https://hdl.handle.net/2142/20449
Description
Title
A scanning tunneling microscopy study of metal films and supported gold particles
Author(s)
Thomas, Patrick Allen
Issue Date
1989
Doctoral Committee Chair(s)
Masel, Richard I.
Department of Study
Chemical and Biomolecular Engineering
Discipline
Chemical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Chemical
Language
eng
Abstract
A new type of Scanning Tunneling Microscope (STM) was designed and constructed to study the surface morphology of small catalyst particles. This is the first application of the STM in the study of supported metal particles. The STM was used to study the surface morphology of Au/Pd films that were sputter deposited onto mica and subsequently sintered in air, as well as equilibrium gold particles formed and supported on graphite. New structures were observed on both the film and particle samples. The surfaces are very rough on the nanometer scale range that the STM can easily resolve.
The Au/Pd films were observed to deposit uniformly on atomically fat mica even at low thickness (50 A). Annealing the metal film resulted in surface roughening, and particle-like formations on the surface. The smooth film character disappeared after short annealing times, and extended annealing resulted in discontinuous film samples that could no longer be imaged with the STM.
The surface roughness of small gold particles supported on graphite appeared to be dependent upon the particle size. Small particles ($$300 A) were seen to possess a wavy surface with generally smooth features.
The significance of these results is greatest in the field of heterogeneous catalysis. The structures observed on these small, model catalyst materials, may provide an insight into the structure/function relationship of supported metal catalysts. Processing conditions appear to influence the surface structure of these small particles, perhaps allowing more specific catalyst preparations to be developed.
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