Studies of Thin Film Nucleation Kinetics (Island Growth)
Lee, Yung-Woo
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https://hdl.handle.net/2142/71833
Description
Title
Studies of Thin Film Nucleation Kinetics (Island Growth)
Author(s)
Lee, Yung-Woo
Issue Date
1986
Department of Study
Metallurgy and Mining Engineering
Discipline
Metallurgical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Materials Science
Abstract
Thin film nucleation theory for the island growth model has long been a subject of intensive study because understanding of the nucleation mechanisms should improve the attainable film morphologies. In spite of the long history of nucleation theory, the current status of the theory is not able to identify controlling factors which govern final film morphologies. The purpose of this thesis is to improve our understanding of thin film nucleation mechanisms.
Kinetic nucleation theory (often called rate theory) has been modified by this study to include parameters such as small cluster dissociation, dimer mobility and defect density. A new numerical analysis technique was developed to solve a set of rate equations without using assumptions regarding steady state or equilibrium state. Based on the results of numerical analysis, it is possible to develop analytical solutions for preferential nucleation at defect sites. These equations are quite different from those corresponding ones which have previously appeared in the literature. The major findings of this thesis are as follows: (1) Steady state with equilibrium monomer density is not a valid assumption for condensation on a defect free substrate because it violates the mass balance law. Quasi-steady state is possible only for a defect controlled nucleation mechanism. (2) The dissociation energy for a Au dimer at a NaCl substrate defect site is about 0.6 eV, which is substantially lower than the conventionally assumed value of 2.23 eV for a perfect site. (3) Since the Au dimer dissociation energy is low, dimer mobility and hence cluster mobility is not an important factor for Au deposition on NaCl. (4) Condensation coefficient data are a very sensitive way to test thin film nucleation kinetics. (5) The size of the critical nucleus could change during the condensation process. (6) Preferential nucleation of defect sites and the dissociation of small clusters are controlling factors for the thin film nucleation based on an island growth model.
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