Graduate Thesis Or Dissertation
 

Development and Applications of Oxide Thin Films using Atomic Layer Deposition and Prompt Inorganic Condensation

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/g158bp329

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  • In the first part of this work, thin films of Al₂O₃ deposited via atomic layer deposition (ALD) are demonstrated to improve the thermal stability of cellulose nanocrystal (CNC) aerogels. ALD is a chemical vapor deposition (CVD) like method in which sequential precursor exposures and self-limited surface reactions produce a conformal thin film with precise thickness control. The conformal nature of ALD is well suited to coating the porous microstructure of aerogels. SEM micrographs of coating thickness depth profiles are shown to agree with trends predicted by precursor penetration models. Thermogravimetric analysis shows samples coated with ALD Al₂O₃ have increased decomposition temperatures.In the second part of this work, ALD zinc tin oxide (ZTO) is used to demonstrate a technique for measuring the substrate inhibited growth in multicomponent and laminate ALD systems. The thickness control of ALD makes it attractive for multicomponent and laminate systems. However, the surface reactions of ALD mean that the first few cycles, while the film nucleates, may have a different growth per cycle (GPC) than when the film is growing on itself in a bulk growth regime. A model for the substrate inhibited ALD of ZTO is derived from two complementary sets of laminates. The thickness and composition predictions of our model are tested against the bulk GPC of ZnO and SnO₂.In the final part of this work, prompt inorganic condensation (PIC) is explored as a potentially more environmentally friendly alternative to ALD for planar thin film applications. Whereas ALD requires expensive vacuum systems and has low precursor utilization, solution based methods, such as PIC, allow atmospheric processing and precursor recycling. The water based PIC solutions use nitrate counter ions which evaporate at low temperatures. Combined with the low energy required to convert the hydroxide precursor clusters into an oxide film makes PIC a promising low temperature route to dense solution processed thin films. The dielectric performance of PIC Al₂O₃ is shown to be comparable to ALD Al₂O₃ films on Si though a large interfacial SiO₂ layer is found to be dominating the behavior of the PIC films. This interfacial layer is shown to form very quickly (≤ 2 min) at low temperatures (≤ 50°C). This low temperature interfacial oxide growth could be a benefit in passivating solar cells.
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