Author ORCID Identifier:
Date of Graduation
7-2026
Document Type
Dissertation
Degree Name
Doctor of Philosophy in Materials Science & Engineering (PhD)
Degree Level
Graduate
Department
Materials Science & Engineering
Advisor/Mentor
Coridan, Robert
Committee Member
Heyes, Colin
Second Committee Member
Hu, Han
Third Committee Member
Kohanek, Julia
Fourth Committee Member
He, Maggie
Keywords
functional nanolaminates, Atomic layer deposition (ALD), nanoscale stratification, effective medium approximation (EMA), transparent conducting oxide (TCO)
Abstract
Atomic layer deposition (ALD) enables precise cycle by cycle control over film thickness and composition. This kind of control is ideal for the engineering of functional nanolaminate coatings with tailored optical properties. Since ALD synthesized composite films are deposited as discrete, stratified layers and not as homogeneously intermixed solids, it is not yet clear when such composites can be be treated with the effective medium approximation (EMA). EMA is simplification that is important to the design of mixed oxide coatings. This dissertation addresses that question using a model system, and then asks whether the same approach can be used to design a material with more than one functional property. The Al2O3-TiO2 system isolates the dielectric version of the problem. Transfer matrix simulations of stratified multilayers were compared UV-Vis measurements of ALD-grown films. A simple composition-weighted EMA accurately describes the transmittance and reflectance of the composite films once individual layer thickness falls below approximately 10 nm. The ZnO-TiO2 system extends this framework to a transparent conducting oxide (TCO), balancing optical tailorability while maintaining electrical conductivity. Optical simulations again converged toward the EMA limit below roughly 10nm. Four-point probe measurements showed a sheet resistance minimum of 1712 Ω sq-1 near 34% TiO2, improving on ZnO rich films (2033 Ω sq-1) and outperforming TiO2 rich films (4978 Ω sq-1). In-situ growth monitoring revealed interface dependent transients relevant to the design of superlattices for the ALD synthesis. These results establish that nanoscale stratification can be used as a design tool to validate EMA in ALD grown composite films.
Citation
Muhanga, J. (2026). Designing Functional Nanolaminates from Complex Atomic Layer Deposition Reactions. Graduate Theses and Dissertations Retrieved from https://scholarworks.uark.edu/etd/6407
