本實驗利用銅氧化物及金修飾氧化鋅奈米柱作為氣體感測材料，進行NO2氣體感測、溫濕度效應分析、選擇性測試及戶外環境感測之實驗，探討本感測材料在戶外實際應用上對NO2的感測效果及老化的現象。
首先以黃光微影與電子束蒸鍍，在四吋矽晶圓上製作出金/鈦金屬電極，再以大面積水熱法成長氧化鋅奈米柱於矽晶圓上，並以光還原法修飾金奈米粒子及銅氧化物於退火氧化鋅奈米柱上，形成銅氧化物/金/氧化鋅三元複合材料，製作出感測晶片。由掃描式電子顯微鏡(SEM)觀察材料之表面形貌，氧化鋅奈米柱為直徑約100 nm之六角柱結構，長度約2 μm；而銅氧化物/金/氧化鋅複合材料則在氧化鋅奈米柱頂端及側壁均勻分佈直徑約200 nm之銅氧化物團簇。
以紫外光激發模式進行NO2氣體感測，並將氣體吸附於材料造成的電阻變化率定義為響應。感測晶片在100 ppb NO2下，其響應值為209%。感測晶片對5 ppb ~ 100 ppb NO2之響應與濃度呈線性關係，其靈敏度約0.02 ppb1。當環境溫度由15 oC上升到50 oC時，感測晶片之電阻會隨之增加，其斜率約2 k oC1。在定溫環境下，感測晶片在相對濕度0.5以上之環境，電阻會隨濕度上升而增加；對100 ppb NO2之響應會在相對濕度0.5時達到最大值。對感測晶片進行不同氣體之感測實驗，晶片對NO2具有最大之靈敏度，O3次之，而對O3之靈敏度約為對NO2之靈敏度的三分之一。
將手持式感測器與感測晶片放置於新北永和測站進行戶外27天監測，分別以NO2感測數據搭配溫濕度修正及人工神經網路兩種方法進行感測器氣體濃度計算，並比對測站氣體濃度值。整體來說，以人工神經網路計算的表現更加出色，感測器與測站數值之決定係數可達0.35。以掃描式電子顯微鏡(SEM)、能量色散X-射線光譜儀(EDS)及X-射線光電子光譜(XPS)分析感測晶片在戶外監測前後材料的變化。氧化鋅奈米柱受到腐蝕由六角柱轉為圓柱，且材料的表面增加了N及S之元素訊號，推測硫酸及硝酸與銅氧化物發生化學反應形成硫酸銅及硝酸銅。除此之外，CuO與Cu2O之比值由監測前的1.12上升至9.09，顯示Cu2O在潮濕環境下與氧氣發生氧化反應而使材料使用初期不穩定，當Cu2O轉變成CuO後，感測材料會趨於穩定。
綜合以上，本實驗之銅氧化物/金/氧化鋅複合材料成本低，對NO2具有高靈敏度，透過溫溼度效應的數據及人工神經網路計算可以更精確地得到戶外NO2氣體濃度。

The goal of this study is to develop a chemiresistive gas sensor for field monitoring of environmental NO2 content. A copper oxide/gold/zinc oxide ternary nanocomposite was prepared for NO2 sensing. The temperature and humidity effects and the selectivity over various gases were investigated in detail. The aging of the nanocomposite in the field was also analyzed.
First, Au/Ti electrodes were made by photolithography and e-gun evaporation on the 4-inch Si wafer. ZnO nanorods (NRs) were grown by using a large area growth of a low-temperature hydrothermal method on the wafer. Au nanoparticles (NPs) and CuxO clusters were then reduced on annealed ZnO NRs by using a photoreduction method to become CuxO/Au/ZnO sensor chips. Scanning electron microscopy was used for morphology analysis of the materals. ZnO NRs were hexagonal structure with 100 nm in diameter and 2 μm in length. CuxO clusters were found on ZnO NRs with 200 nm in diameter in CuxO/Au/ZnO.
UV activation was used for NO2 sensing, and the definition of response was the variation in resistance. The response was 209% for 100 ppb NO2. At 5 ppb ~ 100 ppb, the response was linear with the concentration for sensor chip, and the sensitivity was 0.02 ppb1.When the environmental temperature increased from 15 oC to 50 oC, the resistance of the sensor chip also increased. At constant temperature, 0.5 ~ 1 relative humidity (RH), the resistance of sensor chip increased with RH. The maximum response occurred at 0.5 RH for 100 ppb NO2. We did the different gas sensing measurement for sensor chip, and showed the highest sensitivity for NO2. The O3 sensitivity was about one-third of the NO2 sensitivity.
The portable gas sensor with sensor chip was placed in Yonghe monitoring station in New Taipei city for the 27-day field test. Two different methods were used for the gas concentration calculation. One of the method was calculated by NO2 sensing results including temperature and humidity effects, and the other one was calculated by artificial neural network (ANN). In short, ANN showed the better results, and the determination of coefficient was 0.35. Scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) were used to analyze the change of the sensor chip after 27-day field test. ZnO NRs were corroded, and the morphology transformed from hexagonal structure into cylinder. N and S signal were detected on the surface of the sensor chip because of the formation of CuSO4 and Cu(NO3)2. In addition, the ratio of CuO and Cu2O changed from 1.12 to 9.09 after the field test. Cu2O would react with oxygen under humid environment and become CuO. Once Cu2O oxidized to CuO, the materials became more stable.
In conclusion, low-cost CuxO/Au/ZnO sensor chip was highly sensitive to NO2. It could monitor environmental NO2 content more accurately by using temperature effect correction, humidity effect correction and ANN calculation.

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