本研究係以射頻磁控濺鍍法沉積之氧化鎳薄膜製作延伸式閘極場效電晶體pH值感測器，旨在研發具高量測精準度、高量測靈敏度、高穩定度、可快速反應、可應用於即時監測之pH酸鹼值感測器，以期未來可結合物聯網技術，在各項產業做出貢獻。
首先以射頻磁控濺鍍系統來製備氧化鎳薄膜，並於爐管中以不同溫度進行退火製程，進而探討不同條件製備之薄膜其結晶性、表面結構以及鍵結特性分析。在結晶性的分析上，透過XRD分析發現氧化鎳的結晶性隨著退火溫度上升而提高。在薄膜表面結構上，透過掃描式電子顯微鏡可以見到薄膜表面皆沉積得非常均勻，並且晶粒尺寸隨著退火溫度的提升而上升，然而若經過500oC以上的退火，會造成薄膜緻密度的下降，此結果將造成其於pH感測器的應用上會有可靠度的問題。透過XPS分析可發現經400oC退火的氧化鎳薄膜擁有最高比例的陽離子空缺，霍爾量測也顯現退火後之氧化鎳薄膜擁有更高之載子濃度，更適合作為延伸式閘極場效電晶體pH酸鹼值感測器之感測膜。
第二部分以氧化鎳薄膜為感測膜，製作延伸式閘極場效電晶體pH酸鹼值感測器，探討其於pH2-12範圍之感測靈敏度與線性度，可發現與其它如二氧化鈦、二氧化錫、氧化銦錫等薄膜作為感測膜比較，氧化鎳具有幾乎最優異之靈敏度與線性度，代表其具有高準確量測的能力。接著對經過不同退火溫度之氧化鎳薄膜製作之pH值感測器於測量範圍最極端的酸與鹼環境中分別做穩定度測試，可發現於pH12鹼性環境中，各種退火溫度製備的氧化鎳pH感測器皆可維持穩定的感測靈敏度與線性度達到1個月以上的時間；然而於pH2的酸性環境中，未經退火處理的氧化鎳薄膜經過1週後便遭到腐蝕，但經過退火400oC、500oC處理的氧化鎳pH感測器皆可維持穩定的靈敏度與線性度達1個月以上，而經退火600oC的氧化鎳薄膜則在經過2週後遭到腐蝕，推測是因為SEM分析可見的因經過過高溫度退火造成的薄膜緻密度下降而造成腐蝕速度加快、形成可靠度問題。最後將感測器做電流-時間的連續性量測，將感測器在pH2、pH12兩個極端的酸鹼環境中做變換，測試結果發現在極端pH值變化的情況中，本研究之pH酸鹼值感測器皆可在短短幾秒內做出反應，足見其具有作為可即時監控之pH值監測系統之感測器的潛力。

In this study, Extended-Gate Field Effect Transistor based on Nickel Oxide thin film fabricated by Radio-Frequency Sputtering Method was developed. The aim is to develop high-accuracy, high-sensitivity, high-stability, fast-response and real-time monitoring pH sensors, connecting them to the IOT technology and making a contribution to many industries.
First, NiO thin films were fabricated by RF-sputtering system, then they were annealed at different temperature in furnace with a view to investigating the crystallinity, surface morphology, binding and electrical characteristics of the thin films fabricated under different conditions. To crystallinity analysis, the X-ray Diffraction analysis showed that the crystallinity of the NiO thin film was improved as the annealing temperature increases. From the Scanning Electron Microscope images, the thin films were deposited very uniformly, and the grain size increases as the annealing temperature increases. However, with the annealing temperature higher than 500oC, the density of the thin film decreases which bring about a stability problem in the application on pH sensors. XPS analysis showed that the sample annealed at 400oC had the highest ratio of cation vacancies, and the hall measurement showed that the annealed samples had higher carrier concentration, making themselves more suitable as the sensing film of EGFET pH sensors.
At the second part, the EGFET pH sensors based on NiO thin film were developed, and the sensitivity and linearity were investigated at the pH range of 2-12. It was found that it showed almost the best sensitivity and linearity compared to the other sensors which used the other materials such as TiO2, SnO2 and ITO as the sensing membrane. This showed that NiO has the ability to measure the pH value with a high accuracy. Then the stability tests of pH sensors based on NiO thin film fabricated with different annealing temperature were made in the most extremely acid and alkaline environment of the measurement range respectively. It was found that in the pH12 alkaline environment, all NiO pH sensors fabricated with any annealing temperature could maintain stable sensitivity and linearity for at least one month. However, in the pH2 acid environment, NiO thin film without annealing process was corroded within one week, but NiO thin films annealed at 400oC and 500oC could maintain good sensitivity and linearity for at least one month. However, NiO thin film with 600oC annealing process was corroded within two weeks. It was speculated that the decline of the density of the thin film caused by high temperature annealing process bring about the acceleration of corrosion and the problem of reliability. Last, the current-time measurement of the sensor was made. The sensor was switched between the most extremely acid and alkaline environment of pH2 and pH12. From the results, it was found that in the extreme pH value change condition, the EGFET pH sensor could respond within a few seconds. It obviously has the potential to the real-time monitoring pH system.

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