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  • 學位論文

Utilization of Taguchi method to synthesize vanadium dioxide thin films and their application for an active perfect absorber

指導教授 : 嚴大任

摘要


二氧化釩 薄膜為一種熱敏材料,以導體-非導體的相轉化特性著稱。特別是其電性及光學性質受溫度影響而產生之急遽變化,可被應用作為光學開關、微電池、智慧玻璃等不同領域中。二氧化釩的合成方式有許多種,包含脈衝雷射沉積法、溶膠法以及濺鍍製程法。濺鍍氧化製程法是一種新穎的濺鍍法,為一安全、可常溫下濺鍍、高沉積率及相對便宜的方法。 在本論文中,我們將採用兩步驟濺鍍氧化製程方法來合成二氧化釩薄膜,並利用田口法來找出最佳化之製成參數。由於以往文獻中的兩步驟濺度氧化製成方法所合成的二氧化釩薄膜,其電阻差異僅達到數百倍,相對比其他濺鍍合成製程之電阻差異卻可高達數萬倍,而且以濺鍍氧化製程方法合成的二氧化釩薄膜,其在金屬態的電阻率僅約達10^-2(Ohm-cm),比起濺鍍方法電阻率可達到10^-3(Ohm-cm)更高一些,代表著兩步驟濺度氧化製成方法所合成出的二氧化薄膜特性較差。因此,我們採用田口法來改善兩步驟濺鍍氧化製程合成法所得二氧化釩薄膜的電阻差異、及金屬態的電阻值。所合成出的氧化釩薄膜,含有二氧化釩與三氧化二釩(V2O3)的混和成分,其電阻差異可達到10^4倍,並且其在金屬態的電阻值為1.9x10^-3(Ohm-cm),兩者結果對比從前濺鍍氧化製程方法皆有明顯改善。 另一方面,藉由變異數分析,我們可以推算出各成分因子影響最佳化結果的比例。我們發現氧化溫度為氧化製成中,影響最顯著的因素。並且我們由單因子分析實驗,來確認最佳合成參數,並且探討不同氧化溫度與不同氧化釩成分的關係。 對於合成出的二氧化釩薄膜來做應用,我們展示了以超材料的結構來設計主動吸收體元件,其可作為開關設計,展現吸收狀態與反射狀態。並且,這個主動吸收體元件,可藉由調整結構參數,可在不同頻段上做運用。

並列摘要


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

參考文獻


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