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Evolution of Surface Morphology and Chemistry in ZnO Thin Films and Steel Surfaces studied by Synchrotron X-ray Spectroscopy and Imaging

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dc.contributor.advisor Chen-Wiegart, Yu-chen Karen en_US
dc.contributor.author Jiang, Hua en_US
dc.contributor.other Department of Materials Science and Engineering en_US
dc.date.accessioned 2017-09-18T23:49:53Z
dc.date.available 2017-09-18T23:49:53Z
dc.date.issued 2016-12-01 en_US
dc.identifier.uri http://hdl.handle.net/11401/76044 en_US
dc.description 53 pg. en_US
dc.description.abstract Thin film and surface treatment play an important role in developing materials with unique properties. They have been widely used in energy generation and storage, optical devices, LEDS, electrical semiconductor devices, etc. The stability and functionality of them under operational environment are important, especially the surface morphology and chemical evolution at micro-scale. This information is critical to understand the behaviors of the materials under various environments for a wide range of applications. Synchrotron x-ray fluorescence (XRF) and x-ray absorption near edge structure (XANES) are suitable techniques on investigating surface morphology and chemical evolution. Here, we use both techniques to investigate chemical and morphological heterogeneity of zinc oxide thin films after environmental humidity exposure, as well as surface and chemical evolution of iron oxidation states during iron redox process for samples with/without surface anti-corrosion treatment. Zinc oxide (ZnO) thin films have been reported to suffer from degradation in electrical properties, leading to failure of electronics due to environmental factors, such as heat and humidity. While degradation appears to be linked to water and oxygen penetration in the ZnO film, a direct observation in ZnO film morphological evolution, in conjunction with structural and chemical changes is lacking. Here, we systematically investigated the chemical and morphological heterogeneity of ZnO thin films caused by steam treatment. X-ray fluorescence microscopy, absorption spectroscopy, grazing incident small angle and wide angle scattering, scanning electron microscopy (SEM), ultra-high-resolution SEM and optical microscopy were carried out to examine ZnO, Al-doped ZnO and Ga-doped ZnO thin films, on two different substrates – silicon wafer and PET film. The environmental aging introduced pin-holes in the un-doped ZnO thin film. More significant morphological features formed in the Al-doped ZnO thin films after treatment, with platelet-shaped structures that are 100-200 nm wide by 1µm long. In addition, Zn heterogeneity, anisotropic structure and disordering were also observed in the aged Al-doped ZnO thin films using synchrotron x-ray characterization. X-ray diffraction and absorption spectroscopy indicate the formation of a zinc hydroxide in Al-doped films due to environmental aging. Utilizing advanced characterization methods, our studies provide information with unprecedented level of details and reveal the chemical and morphologically heterogeneous nature of degradation in ZnO films. Anti-corrosion coating is widely used on industrial steel products. While the effect of these coatings is proven to be positive, fundamental studies on the chemical evolution of the protected metal is lacking. Here, we conducted in situ x-ray spectroscopic experiment to observe the process of steel corrosion with and without the protective coating. X-ray fluorescence mapping was conducted to observe surface morphology and elemental distribution during redox process. X-ray absorption near-edge structure spectroscopy was performed to determine the oxidation states and chemical information of Fe. Steel without coating was corroded rapidly and homogeneously, within 1 hour. Steel with anti-corrosion Zr-based (Henkel Corporation) coating showed good resistivity to corrosive environment (5wt% NaCl solution). Only very slight local oxidation was observed after approximately 10 hours of treatment. Our study laid foundation for possibility to conduct in situ research on numerous materials under various environments. en_US
dc.description.sponsorship This work is sponsored by the Stony Brook University Graduate School in compliance with the requirements for completion of degree. en_US
dc.format Monograph en_US
dc.format.medium Electronic Resource en_US
dc.language.iso en_US en_US
dc.publisher The Graduate School, Stony Brook University: Stony Brook, NY. en_US
dc.subject.lcsh Materials Science en_US
dc.subject.other Anti-corrosion, Oxidation states, Synchrotron, Thin film, XANES, X-ray fluorescence en_US
dc.title Evolution of Surface Morphology and Chemistry in ZnO Thin Films and Steel Surfaces studied by Synchrotron X-ray Spectroscopy and Imaging en_US
dc.type Thesis en_US
dc.mimetype Application/PDF en_US
dc.contributor.committeemember Koga, Tadanori en_US
dc.contributor.committeemember Petrash, Stanislas. en_US

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