人類科技的蓬勃發展給予我們一個智慧、便利的生活模式，然而，科技進步的背後卻也連帶造成環境和健康上的隱憂，隨著暴露在揮發性有機氣體的濃度不同會對人體的健康造成一定程度的傷害，因此氣體感測器已經被廣泛應用於化學工業、生物醫療、農業、食品工業以及環境檢測等領域。此篇論文所製作的三氧化鎢系氣體感測器具備良好的化學穩定性、極佳的氣體選擇性、高靈敏度及製作過程簡單等優點。此外，本論文也藉由X光薄膜繞射分析儀、掃描式電子顯微鏡、能量散式光譜儀、原子力顯微鏡等儀器來分析三氧化鎢系氣體感測器之元件結構、表面型態和元素組成。
在元件製程方面，吾人利用熱蒸鍍沉積鉻/鉑指叉式電極於藍寶石基板上，接著以射頻磁控濺鍍的方式製做三氧化鎢薄膜感測層，最後使用快速熱退火增進三氧化鎢薄膜的結晶性，並將元件針對不同濃度的氨氣進行感測分析。
其次，吾人利用濕式製程的方式合成出鉑奈米粒子修飾三氧化鎢薄膜感測層表面，改善三氧化鎢系氣體感測器之操作溫度、靈敏度及氣體選擇性。在研究上已有諸多證據顯示鉑奈米粒子對氫化物而言是一個良好的催化劑，體表面積的增加除了能提供較多的氣體吸附座外，溢出效應的產生更促進電子在材料表面的傳導和反應。實驗結果顯示經鉑奈米粒子修飾後的元件對氨氣有良好的感測能力。
最後，吾人以熱蒸鍍沉積鉑奈米粒子修飾三氧化鎢薄膜感測層表面，同樣藉由鉑奈米粒子去催化元件對氨氣與氫氣的反應。從實驗結果可以發現，利用熱蒸鍍所沉積的鉑奈米粒子比起濕式製程，在氨氣與氫氣的感測能力均有大幅度的提升。

The flourishing development of human science and technology has given us a smart and convenient lifestyle. However, technological progress has also brought about environmental and health concerns. With exposure to different concentrations of volatile organic compounds (VOCs), it will affect human health and cause a certain degree of damage. So, gas sensors have been widely used in the chemical industry, biomedical, agricultural, food industry and environmental testing, etc. Tungsten trioxide (WO3) based gas sensors studied in this thesis have the advantages of good chemical stability, excellent selectivity, high sensitivity and simple manufacturing process. In addition, this study will analyze the device structure, surface morphology and elemental composition of WO3 based gas sensors by X-ray diffractometer (XRD), scanning electron microscope (SEM), energy dispersion X-ray spectrometer (EDS), and atomic force microscope (AFM).
In terms of device processing, the chrome/platinum (Cr/Pt) interdigitated electrodes were fabricated on a sapphire substrate by the thermal evaporation (TE) method. Followed by a radio-frequency (RF) sputtering method deposited the WO3 thin film sensing layer. Then, the crystalline of WO3 thin film was improved by rapid thermal annealing (RTA). Finally, the sensing characteristics under exposure to various concentrations of ammonia were discussed.
After that, we used a wet process to synthesize platinum nanoparticles (NPs) as the catalytic metal to modify the surface of WO3 thin film sensing layer. It improves the performance of operating temperature, sensitivity, and selectivity of WO3 based gas sensors. Many studies have shown that Pt nanoparticles are a good catalyst for hydrides. The increase in surface-to-volume ratio can provide more gas adsorption sites, and the resulting spillover effect facilitates electron conduction and reaction at the surface of the material. The experimental results show that the nanoparticle-modified device has good sensing properties for ammonia.
In the next chapter, we modified the surface of WO3 thin film sensing layer with depositing Pt nanoparticles by the thermal evaporation. Pt nanoparticles were used to catalyze the reaction of ammonia and hydrogen. From the experimental results, it was found that Pt nanoparticles deposited by thermal evaporation compared to the wet process have a significant increase at the sensing properties of ammonia and hydrogen.

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