本研究係以二氧化鈰/摻氟氧化錫(CeO2/FTO)感測膜製作延伸式閘極場效電晶體式(EGFET)酸鹼度感測器，旨在探討製備變因對薄膜性質及感測特性之影響，並找尋最佳製備條件。
研究中首先以FTO製作元件，在20oC下進行pH感測之探討。結果發現，FTO元件在pH 4-10間具有相當良好之感測靈敏度(74.9 mV/pH)，但因耐酸鹼性不佳，因此pH量測範圍受限。為改善FTO膜性質及pH感測特性，本研究中提出以CeO2奈米粒子來修飾FTO膜，製成CeO2/FTO感測元件。
實驗中採用沉澱法來製備CeO2奈米粒子，並以旋轉塗佈方式沉積於FTO基材上；改變製備條件，包括：固含量、塗佈轉速、煅燒溫度、沉澱劑濃度及塗佈次數等來加以探討。結果發現，隨固含量或塗佈次數增加時，CeO2沉積量隨之增加，膜表面之活性座亦增加，因此元件之pH感測靈敏度增高；但當沉積量過高時，由於膜層電阻遽增，導致靈敏度下降。當煅燒溫度提升時，由於CeO2晶粒增大，有利於訊號傳遞，而致靈敏度增高；但若提高沉澱劑濃度時，所得CeO2粒徑增大，造成膜表面活性座減少，故使靈敏度下降。實驗結果亦顯示，CeO2/FTO元件之最佳製備條件為：沉澱劑濃度3 M、固含量0.5 wt%、塗佈轉速2000 rpm、煅燒溫度600 oC、塗佈一次；在20oC下、pH 1-13間，該元件（S05R20T6）之感測靈敏度可達75.1±0.9 mV/pH，遠高於Nernstian極限(即58.2 mV/pH @ 20oC)，線性度為0.9997，感測範圍為pH 1-13。此外，由溫度、遲滯、時漂等效應及選擇性之探討結果發現，此元件之耐酸鹼性良好、耐用性長、穩定性佳、離子選擇性高，且量測範圍寬廣；尤值一提的是，遲滯壓差僅8.9 mV，與FTO元件(遲滯壓差39.2 mV)相比較，更顯示此元件之感測優勢。
綜上所述，以CeO2奈米粒子來修飾FTO元件，確能改善感測膜層之耐酸鹼性，進而提升CeO2/FTO元件對pH之感測性能，因此元件在應用上具有極佳之發展潛力。

In this work, CeO2/FTO pH sensors based on extended gate field-effect transistor (EGFET) were fabricated. The influences of preparation variables on properties of CeO2/FTO films were investigated. The sensing characteristics of CeO2/FTO devices toward pH were also studied for searching an optimum preparation condition. Experimentally, CeO2 nanoparticles prepared by the precipitation method were spin-coated on the FTO substrate. The influences of preparation variables including solid content, spinning rate, calcination temperature, precipitant concentration and coating cycle on the pH sensing characteristics of resulting devices were studied. Among the studied CeO2/FTO devices, the best device (S05R20T6) demonstrated excellent sensing characteristics with super-Nernst limit sensitivity of 75.1 mV/pH (58.2 mV/pH @ 20 oC) and the linearity of 0.9997 at 20 oC, which was prepared under precipitant concentration of 3 M, solid content of 0.5 wt%, spinning rate of 2000 rpm, calcination temperature of 600 oC and spin cycle of 1. From the investigation of temperature, hysteresis, drift and selectivity, it indicated that the S05R20T6 device showed good acidic and alkaline resistances, long-term durability, high stability and selectivity, suitable to be used over a wide pH range. In conclusion, the CeO2/FTO device indeed exhibited excellent sensing performance superior to FTO device, especially promoting the ability against extreme pH conditions. Accordingly, it is prospective that the CeO2/FTO device have great promising potential in pH measurements for wide applications.

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