本研究提出創新紫外光輔助奈米氧化鋅薄膜，應用於低工作溫度之高效能氧氣感測器。本研究使用溶膠─凝膠法與水熱法，於具有指叉狀電極的玻璃基板上，合成氧化鋅奈米柱。使用80 mW且波長370 nm的紫外光發光二極體，可提高奈米氧化鋅薄膜的感測效能。結果顯示奈米氧化鋅氧氣感測器的效能明顯提高。使用紫外光照方式可將感測器的工作溫度降至50˚C，而傳統金屬氧化物形式的氧氣感測器，其工作溫度約350˚C，相較之下，本研究提出的氧氣感測器，其工作溫度顯然較低許多。相較無紫外光照的氧化鋅奈米柱，使用紫外光照可使氧化鋅奈米柱的感測效能提高4.66倍。對於低工作溫度的氧氣偵測，本研究提出一種簡單而高效能之方法。
氧化鋅已被使用作為氧氣，或是有機揮發性氣體的感測材料。傳統固態形式的氣體感測器，其必須依賴300 - 350˚C的高工作溫度，提升載子的移動能力，以達到偵測的目的。此方法不僅會耗損加熱感測元件所需要的能量，也將縮短感測器的使用壽命。而氧化鋅為II – VI族的半導體，其能隙為3.3 eV，所以紫外光照射是一種能有效在氧化鋅表面產生大量電洞─電子對的方式，可使氧化鋅為感測材料的氣體感測器效能提升。若使用此發方式，可使感測器免於高工作溫度環境中運作。氧氣分子具有高陰電性，其將吸引由紫外光產生的自由電子形成O2¯，使自由電子數量下降，而導致電阻值上升。本研究使用一種簡便的製程，製作氧化鋅氧氣感測器，奈米氧化鋅的感測區域面積為8.0 mm x 8.0 mm。
XRD圖譜顯示(002)平面具有最強的繞射強度，表示氧化鋅奈米柱延c軸方向生長，其具有高度方向性。由SEM影像觀察成長奈米柱之前的氧化鋅晶種層，可見極微小的球狀奈米粒子，約15 nm。氧化鋅奈米柱傾向沿基板的垂直方向生長，其長度約600 nm。本研究也使用不同奈米氧化鋅薄膜，於工作溫度50˚C，量測晶片對於97%氧氣的感測效能。結果顯示，紫外光照氧化鋅奈米柱具有最佳的感測效能。對於感測晶片的每一個工作溫度，紫外光照氧化鋅奈米柱的感測效能，其均較無紫外光照者高。使用紫外光照氧化鋅奈米柱，進行97%氧氣的三次重複性量測，評估感測器的重複使用性，計算三次量測的差異量為3.3%，表示本研究提出的氧氣感測器具有重複使用的特性。紫外光照氧化鋅奈米柱偵測5 mTorr至1000 mTorr的氧氣濃度，其具有良好的線性度(R2=0.9952)，此確立本研究提出的氧氣感測器具有良好的感測效能，且偵測極限可至5 mTorr。本研究發展紫外光照氧化鋅奈米柱的氧氣感測器，其表現高效能，且可於低工作溫度運作的潛力。

This work presents a novel ultraviolet irradiation assisted nanostructured ZnO film for high performance oxygen sensing under a low working temperature. Nanorod ZnO structures are synthesized on a glass substrate with interdigital sensing electrodes utilizing the developed two-stage sol-gel and hydrothermal processes. An 80 mW LED with the emission wavelength of 370 nm is then used to enhance the sensing performance of the nanostructured ZnO film. Results indicate that the sensing performance of the nano ZnO oxygen sensor is greatly improved. The oxygen sensor can work at a low temperature of 50˚C with the assist of UV exposure, which is much lower than the working temperature of typical solid state metal oxide sensors of around 350˚C. The response of the UV-assisted ZnO film shows 4.66 times larger than the same film without UV exposure. The method developed in the present study provides a simple yet high performance method for oxygen sensing under low operation temperature.
ZnO has been used as the sensing material for oxygen or volatile organic compound (VOC) sensing. Typical solid state gas sensors rely on an operation temperature of 300 - 350˚C to enhance the carrier mobility of the metal oxide for sensing purpose. This approach usually consumes more energy for heating the sensing element and also significantly reduces the lifetime of the sensor. Alternatively, zinc oxide is II-VI group semiconductor with a wide band gap of 3.3 eV. UV exposure is an efficient way to produce hole-electron pairs in ZnO surface to enhance the sensing performance of ZnO-based gas sensor. With this approach, high operation temperature can be excluded for gas sensing. Adsorbed oxygen molecules will attract the UV induced electrons and form O2¯ due to the large electronegativity, resulting in the resistance incensement of the sensing layer due to the decease of electron carriers. A simplified process is used for producing the ZnO-based oxygen sensor. The sensing area for the nanostructured ZnO is 8.0 mm x 8.0 mm.
The XRD patterns of the ZnO nanorods presents strong diffraction peak of (002) illustrates that the high tendency of ZnO nanorods growing along the c-axis. The SEM image shows the synthesized ZnO seed layer prior to the growth of nanorods. Ultra-fine ZnO nanospheres are about 15 nm on the substrate. The growth of the nanorods is preferred in the direction perpendicular to the substrate. The length of ZnO nanorods is about 600 nm. The measured response for sensing 97% oxygen is used various ZnO sensing layers with and without UV exposure at a low temperature of 50˚C. Results show that the nanorod ZnO film with the assist of UV exposure exhibits higher response. The response of UV-assisted ZnO nanorods was significantly higher than the same film without UV irradiation at all operation temperatures. The measured result of the 97% oxygen for three repeating tests evaluates the sensing repeatability of the developed sensor. The calculated variation for these three measurements was only 3.3%. The nice linearity (R2=0.9952) from 5 to 1000 mTorr confirms the good sensing performance of the developed sensor. Result also indicates that the detection limit of the sensor can be as low as 5 mTorr. The developed oxygen sensor utilizing UV-assisted ZnO nanorods has shown its potential to be a high performance oxygen sensor which can work at a low temperature.

致謝 i
中文摘要 ii
Abstract iv
目錄 vi
圖目錄 ix
表目錄 xi
符號表 xii
簡寫表 xiv
第一章 緒論 1
1.1 前言 1
1.2 氧氣對人體的重要性 2
1.3 氣體感測器種類 2
1.3.1 順磁式氣體感測器 3
1.3.2 電化學式氣體感測器 4
1.3.3 石英晶體微天平氣體感測器 7
1.3.4 表面聲波氣體感測器 8
1.3.5 光學式氣體感測器 9
1.3.6 金屬氧化物半導體式氣體感測器 10
1.4 論文架構 13
第二章 動機目的及原理 14
2.1 文獻回顧 14
2.2 實驗動機與目的 19
2.3 原理 20
2.3.1 氧化鋅材料特性 20
2.3.2 氣體感測原理 21
第三章 材料與方法 24
3.1 電極晶片製作 24
3.1.1 電極基板製作 24
3.1.2 指叉狀電極製作 24
3.2 奈米氧化鋅合成 27
3.2.1 溶膠─凝膠法 27
3.2.2 水熱法 28
3.3 量測系統 31
3.3.1 玻璃罩腔體 31
3.3.2 濺鍍系統專用高真空腔體 32
3.3.3 資料擷取系統 33
第四章 實驗結果與討論 35
4.1 結晶結構與表面形貌分析 35
4.1.1 結晶結構分析 35
4.1.2 表面形貌分析 37
4.2 奈米氧化鋅能隙量測 39
4.3 光照對感測效能影響 40
4.4 工作溫度對感測效能影響 42
4.5 感測器基本特性量測 45
4.5.1 奈米氧化鋅結構對感測效能影響 45
4.5.2 感測器反應時間量測 46
4.5.3 重複性量測 47
4.6 氧氣濃度偵測效能 48
第五章 結論與未來展望 55
5.1 結論 55
5.2 未來展望 57
參考文獻 58
自述 63

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