Growth and characterization of polymer thin films grown using molecular layer deposition with heterobifunctional precursors

Zachary Michael Conway Gibbs
Abstract & Cover

Gibbs, Zachary Michael Conway (MS, Chemical Engineering) Growth and Characterization of Polymer Thin Films Grown Using Molecular Layer Deposition with Heterobifunctional Precursors Thesis Directed by Professor Steven M. George In this work, growth of thin polymer films using molecular layer deposition with heterobifunctional precursors is investigated. Several growth phenomena are observed including: loss or gain of reactive sites as a result of precursor reactivity or vapor pressure; precursor diffusion and reaction within the porous polymer film; and crosslinking. Reactions were investigated using quartz crystal microbalance, Fourier transform infrared spectroscopy, and various ex situ techniques. Reactions involving 4-azidophenylisothiocyanate and 4-aminobenzonitrile were shown to stop growth after only a few cycles which is attributed to a loss in reactive sites which was modeled by an exponentially decaying growth rate. Growth of 4- carboxyphenylisothiocyanate with TMA and water was investigated as well. Active site multiplication as a result of the trifunctionality of the TMA molecule was proposed to explain the significantly higher growth rate for TMA/CI films. TMA/H2O/CI films showed the ability to crosslink through aluminum hydroxyl condensation reactions. Upon increasing the reaction temperature, reactant diffusion was observed in the form of mass removal upon TMA exposure. This same phenomena is thought to be occurring in films grown using Diels-Alder reactions in the third section of this thesis. These films showed a strong growth rate dependence upon reactant purge time and growth temperature. FTIR seems to weakly support Diels-Alder reaction, but it appears that the primary film growth mechanism is through CVD-like diffusion and condensation reactions.

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University of Colorado Boulder
(Boulder, USA)
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