Processing of nanoscale materials Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/t722hf54c

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  • The motivation for undertaking this research was to increase the understanding of processing colloidal semiconductor nanocrystals and thin films metallic glasses to enable their wider application in future devices. This research covered two unique materials, lead selenide (PbSe) nanocrystals and thin film metallic glass alloy of zirconium copper aluminum nickel (ZCAN). Both materials have shown promise in several applications, but have faced barriers that are related to manufacturing. PbSe nanocrystals have several potential applications including photovoltaics, infrared emitting diodes and lasers, nanoscale electronics and thermoelectric devices. The synthesis of nanocrystals has been historically based on small batch reactions that have been difficult to scale up. The objective of this research was to develop a microwave assisted continuous flow synthesis technique as a potential path for scalable synthesis of high quality colloidal semiconducting nanocrystals. PbSe nanocrystals were chosen as a model system because of the ease of binary nanocrystal synthesis, and the increasing interest in the use of PbSe for photovoltaics and infrared emitters. This research was approached in iterative steps starting with batch microwave synthesis followed by microwave assisted segmented flow synthesis. The synthesized PbSe nanocrystals were analyzed using high resolution transmission electron microscopy, energy dispersive x-ray spectroscopy, and x-ray diffraction to determine their size, composition, and crystal structure. Metallic glasses alloys, including ZCAN, have potential applications including nanoscale patterning, micro-electro-mechanical systems, electronic devices, protective coatings, laminates and catalysis. Oxidation is known to affect the physical, electrical, and chemical properties of metallic glasses. Previous research on the oxidation of metallic glasses has focused primarily on long oxidation times for bulk metallic glasses, where oxide growth of a few microns was observed. The objective of this research was to investigate thermal annealing and short oxidation times for thin film metallic glasses, where oxide growth of a few nanometers were studied due to the importance of stable interfaces in electronic devices. For these studies, sputter deposited samples of the thin film metallic glass were oxidized for various lengths of time. Characterization was performed using high-resolution transmission electron microscopy, x-ray photoelectron spectroscopy, and secondary ion mass spectrometry in order to examine the initial growth rate of oxide formation and diffusion induced compositional changes through the thickness of the films.
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