結合微電漿產生單元之氧化鋅氣體感測裝置之建立

Development of a Zinc Oxide Gas Sensing Device with an Integrated Microplasmas Generation Unit

黃非紅(Fei-Hung Huang)

指導教授 ： 徐振哲

國立臺灣大學/工學院/化學工程學研究所/碩士(2017年)

https://doi.org/10.6342/NTU201701522

摘要

常壓微電漿系統由於不需要真空設備、放電體積小且具有高電子密度卻未與環境達熱平衡而溫度較低，而可提供一反應性高、消耗功率低、局部處理可能性、低溫的製程，並且其電極設計組合自由度高，而成為備受矚目之常壓電漿系統。本研究為結合微電漿產生單元與氣體感測元件之裝置：使用氧化鋅之半導體特性作為電導式氣體感測元件，並藉由微電漿放電之位置同時為氧化鋅前驅物沉積處，當微電漿產生時即可對前驅物進行就地處理之特性，於低溫下使前驅物轉化為氧化鋅，而提供一當裝置不耐高溫時之氧化鋅製程選擇。
本研究之微電漿產生單元屬於介電質放電型微電漿，其裝置是由一「金屬—介電質—金屬」之雙面銅箔基板製備而成，藉由碳粉轉印技術使電極圖案具有高設計自由度，並且於約略半小時內即可完成。當於介電質兩側的電極施加高壓交流電時，可於常壓下，在電極邊緣且於另一側有電極的位置產生微電漿。由於可自行定義雙面銅箔基板上的電極圖案，可經由設計電極的排列，將微電漿產生單元與氣體感測元件整合於一裝置上。於雙面銅箔基板之兩金屬面共有三個獨立的電極，其中一面有兩個電極，另一面則為一個電極；位於同一面的兩個電極之間，以一寬度為200 μm的間隙隔開，此間隙之另一面為電極。於間隙處以噴霧法沉積氧化鋅之前驅物後，當微電漿產生於間隙兩旁的電極、並擴散至間隙之間時，則可對沉積的前驅物進行處理，使其轉化為氧化鋅，作為本研究中之氣體感測元件。
本研究之氧化鋅氣體感測元件以對乙醇蒸汽之感測作為測試代表，可藉由調整電漿處理時間、產生電漿時的氣氛、電極圖案的設計等方式來改變或優化氧化鋅氣體感測裝置之感測表現。當使用指叉狀電極設計之裝置時，以空氣下產生之微電漿進行處理10分鐘後，可偵測濃度範圍約為100至16000 ppm之乙醇蒸汽，此時之氧化鋅氣體感測元件之電阻範圍約為100 MΩ至100 GΩ，將氣體感測表現與掃描式電子顯微鏡之能量發散譜儀對微電漿處理後之元素分析結果對照後，證實了經微電漿處理後可將原沉積之前驅物硝酸鋅轉化為半導體氧化鋅。

關鍵字

氣體感測器 ； 氧化鋅 ； 微電漿

並列摘要

Atmospheric microplasma system has numerous advantages, for example, the operation under atmospheric pressure avoids the use of vacuum equipment, the small discharge volume with high electron density and reactivity provides the capability of local treatment and low power consumption, the characteristic of non-thermal equilibrium plasma offers us an option of low temperature process, etc. Therefore, atmospheric microplasma system becomes one of the most attractive plasma systems operated under atmospheric pressure. In this thesis, we integrate the microplasmas generation unit (MGU) with the gas-sensing element on one device. The gas-sensing element is zinc oxide (ZnO), which is widely used as conductometric gas sensors based on its semiconducting property. In this device, the discharge location of microplasmas is also the deposition position of the precursor film of ZnO, thus the MGU provides on-site treatment of the precursor film and converts the film to ZnO film with low processing temperature. This process enables ZnO film fabrication even when the device or substrate suffer from the disability of low temperature tolerance.
In this thesis, the MGU is classified as the dielectric-barrier-discharge (DBD)-type microplasma system. The device was fabricated by double-sided copper clad laminate (CCL), which consists of two copper laminates with one insulting layer between. Through toner transfer process, we are capable to design and fabricate the electrodes’ patterns, as we desire. While the high voltages (AC) are applied across the dielectric layer, microplasmas breakdown along the edge of the electrodes under atmospheric pressure. Because of the capability of user-defined electrode patterns on CCL, we can integrate the MGU with the gas-sensing element on one device. We placed one pair of electrodes on one side of the CCL and one electrode on the other side. The paired electrodes on the same side of the CCL were separated by a 200-μm-wide gap from each other; moreover, on the other side of the gap was electrode. After spraying zinc nitrate, the precursor of ZnO, over the gap for deposition of the precursor film, microplasmas generated along the edge of electrodes and diffuse to the gap, and microplasma post-treatment converted the film to ZnO. Therefore, the film could be treated as a gas-sensing element.
In this thesis, ethanol vapor was the representative gas for the test of gas sensing performance. We changed the microplasma post-treatment time, the ambient for plasma generation, the pattern design of electrodes, etc., to alter or modify the sensing performance. For example, when we used the pattern of interdigitated electrodes and the microplasmas generate under ambient air, for only 10 minutes of microplasma treatment, the sensor detected around 100 to 16000 ppm ethanol vapor with the resistance ranging from about 100 MΩ to 100 GΩ. Besides, comparing the gas sensing performances with the results of element analysis by energy dispersive spectrometer of scanning electron microscope, we concluded that the precursor films successfully transform to semiconductor ZnO.

並列關鍵字

gas sensor ； zinc oxide (ZnO) ； microplasma

參考文獻

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