Synthesis, Characterization, and Applications of ZnO based Nanostructures

安福斯(Manekkathodi Afsal)

指導教授 ： 陳力俊

國立清華大學/工學院/材料科學工程學系/博士(2010年)

https://doi.org/10.6843/NTHU.2010.00278

摘要

This PhD Thesis is entitled as "Synthesis, Characterization, and Application of Zinc Oxide Nanostructures". In this work, we put efforts to explore and expertise in contemporary one-dimensional nanostructures research. The research is focused on ZnO based nanosystems and its novel applications towards present / future technology. We carried out detailed investigations on the following; a) syntheses of ZnO nanostructures on unique substrates, such as paper and other naturally obtained substrates and its applications, b) syntheses of ZnO nanostructures on lotus flower and investigations of the amendment of its superhydrophobicity c) syntheses of ZnO/SiO2 core-shell nanowires and investigations of its field emission and photo-conducting properties, and d) syntheses of ZnO self assembled nanocomb structures and its applications as wave guides arrays as building-blocks for optical circuits.
Systematic investigations of growth conditions to control morphologies on paper substrates were carried at the outset of this work. We achieved controlled array of aligned single crystalline ZnO nanowires on a most economic, highly bendable and environmentally benign paper substrates for the first time. The paper surface modified into various surfaces like conducting and semiconducting surfaces and ZnO nanorods have been fabricated. Furthermore, large scale synthesis of ZnO nanowire arrays is achieved in a reproducible manner. Prototype photo-conducting device as well as ZnO-organic hybrid PN junction devices have fabricated based on the ZnO nanowire arrays that can be strategically exploited to other functional devices and integrated with opto-electrical device components.
We demonstrate a conceptually novel approach to incorporate biological substrates with synthetic nanowires. Vertically aligned single crystal ZnO nanowire arrays were directly grown on the lotus leaf surface using a simple hydrothermal method. We observed strong adhesive superhydrophobicity on this natural / artificial architecture, which is paradoxical to conventional observations on this inspirational superhydrophobic model. To the best of our knowledge, this is the first report on the growth of any kind of synthetic nanostructures on a naturally occurred biological substrate. This unique and distinctive approach has fundamental significance towards technological novelties in the bio-mimetic as well as in nano-biotechnology. We hope ample future for this approach in diverse areas of nanotechnology with strategic exploitation of this "material engineering on real biological surfaces".
We present a direct and reproducible one step technique, for the fabrication of SiO2/ZnO core-shell nanostructures using a CVD system. We observed that, the ZnO semiconducting core is formed first which is followed by the SiO2 sheath. UV photodetectors are fabricated based on these ZnO-SiO2 core-shell nanowires and its photocurrent and its photoresponse measurements were carried out. It is observed that, the photocurrent can be reproducibly switched from "ON" to "OFF" state by modulating photo exposure. Further, it shows rapid response and recovery. Field electron emission from these ZnO-SiO2 core shell nanowires was investigated using a diode structure configuration. These core-shell nanowires showed better field emission property comparing to the ZnO nanowires grown on the same method.
Chemically synthesized nanostructure have several features that make them good photonic building blocks, including inherent one-dimensionality, size control, low surface roughness, a diversity of optical and electrical properties, and the ability to operate above and below the diffraction limit. In this area , Hierarchical assembly of nanoscale building blocks (nanocrystals, nanowires, and nanotubes) is a crucial step toward realization of these functional nanosystems and represents a significant challenge in the field of nanoscale science. By precisely controlling the ZnO nanostructure growth process, we were able to synthesize a high yield, comblike structures, made of periodic arrays of single-crystalline ZnO nanowires, using thermal CVD. Various experimental parameters have been systematically varied and investigated to exploit the morphological control of these nanocomb structures. We investigated the potential of these self assembled nanocomb structures to use as photonic waveguide as an alternate bottom up approach apart from the conventional top down strategy. Waveguide properties are studied using far-field optical microscope techniques. It is expected that ZnO nanocombs can be used as waveguides, which can manipulate the light to an interconnected arrays. We fabricated an integrated photonic device that couples the wave guide arrays with photodetector devices and its performances were analyzed.

關鍵字

氧化鋅

並列摘要

無資料

並列關鍵字

ZnO ； Nanostructures ； Flexible Electronics ； Photodetectors ； Waveguides ； core-shell nanowires

參考文獻

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