Graduate Thesis Or Dissertation
 

Functional materials for advanced energy and electronic devices

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/z316q6416

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  • Advances in energy technologies and electronics have typically occurred through either heightened performance or cost reduction. This dissertation explores both routes through a series of fundamental material studies that may contribute to the enabling of next generation devices. Solution based syntheses and deposition of chemical products offer a low cost alternative to conventional vacuum based methods, and is examined through the wet synthesis of CuZnSnS₄ light absorbing nanoparticles. The nanoparticles were synthesized by both microwave-assisted and continuous flow techniques, and at relatively modest temperatures with inexpensive solvents. Varying the initial concentration of precursors allowed a facile method to modify the nanoparticle composition. For the continuous flow system, consideration of fluid flow dynamics provided a means to control the generation of gas within the reactor to allow for improved mixing. Processing of as-deposited solution based films to form more functional variants was studied in further detail by way of the Hf(OH)[subscript 4−2x−2y](O₂)[subscript x](SO₄)[subscript y]·qH₂O (HafSOx) material system. Surface analytical techniques revealed that control of the catalytically active acid sites may be possible with optimization of water exposure and post-exposure annealing temperature of dehydrated films. Thermal and electron stimulated desorption of peroxide containing HafSOx films revealed complex surface dynamics. The total desorption cross sections of O₂ for 500-2000 eV incident electrons was ~10⁻¹⁶ cm². Interfacial formation and chemistry was investigated by evaporating platinum onto amorphous indium gallium zinc oxide, an increasingly common interface type found in memristors and other novel electronics. Metallic indium formed upon platinum deposition, and the interface had an unexpectedly low Schottky barrier height of 0.25 eV, likely as a result of the reactive interface. Finally, the surface properties of highly oriented LaFeO₃ films were characterized and modified through reductive annealing. Iron was found to exist in three oxidation states depending on the annealing temperature and location within the film. In addition, the concentration and types of oxygen species were also found to vary based on proximity to the surface and the thermal treatment. Together, the aforementioned studies are related by the potential manufacturing steps of inexpensive, innovative energy and electronic devices. These steps include solution synthesis and deposition, processing to form a functional film, interface formation, and adapting the film's surface properties to suit its intended application.
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