| Summary: | 碩士 === 國立清華大學 === 材料科學工程學系 === 102 === Vanadium dioxide (VO2) thin film, which belongs to thermochromic materials has attracted much attention for its drastic changes in the electrical and optical properties owing to the metal-insulator transition (MIT) that have a promising prospect such as optical switching devices, micro-batteries and smart windows. There are many different fabrication methods such as pulsed laser deposition, sol–gel process, and sputtering method. The sputtering oxidation coupling method (SOC method) is a novel sputtering method with two step procedures which is characteristic of safety, sputtering at room temperature, high deposition rate and low cost. However, the reported resistivity change for VO2 thin film deposited by SOC method exhibits only two-order differences compared to four-order difference for other sputtering methods. Furthermore, the resistivity for the metal state of vanadium dioxide in the previous SOC method is around 10-2 (-cm), slightly higher than the other reported values, which is around 10-3 (-cm).
In this thesis, we adopt the Taguchi method to optimize the fabrication parameters of the SOC method. The as-deposit vanadium oxide films contain not only VO2 crystalline but also the component of vanadium sesquioxide (V2O3), which exhibit better metal-like performance of vanadium oxide film. The changes of resistivity for our vanadium oxide thin films possess up to four-order differences and the average resistivity in the metal state is 1.9x10-3 (-cm), which show better results compared to the reported literatures and also validate the efficient optimization of the Taguchi method
In addition, Analysis of variance (ANOVA) is performed to evaluate the significant process factors, which would influence the product quality. We discover the temperature of oxidation dominates in the oxidation process of the SOC method. Furthermore, we have applied one factor analysis not only to confirm the optimal setting of the high performance vanadium dioxide but also to analyze the relation between the oxidation temperature and the components of the vanadium oxide.
As for the application of as-deposit VO2 thin film, we have demonstrated an active metamaterial based perfect absorber both in simulation and experimental results . Our absorber can be function as a switch to separate two distinct states of the absorber and reflector. The device is scalable spanning from the microwave regime to the optical frequency by just changing the sizes appropriately
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