在本論文中，我們研製一系列以三-五族半導體金屬氧化物為基礎之高性能化學電阻式氣體感測器，包含氮化鎵/氮化鋁鎵蕭特基二極體式與以三氧化鎢作為感測膜之化學電阻式之氣體感測器，此兩類感測器皆於元件表面以催化金屬奈米顆粒修飾之。此外，本研究之氮化鎵/氮化鋁鎵蕭特基二極體式器體感測器本身因氮化鎵/氮化鋁鎵介面具有高電子移動率的二維電子氣(2DEG)，當引入待測氣體，蕭特基位能障變化時，可使電流大幅改變，是相當潛力的半導體式氣體感測元件。而本研究之n型三氧化鎢感測膜化學電阻式氣體感測器因為三氧化鎢材料具有高能障之特性(2.6 ~ 2.7 eV)，因此當待測氣體引入時，空乏區寬度變化量較大，相對的電流就會明顯變化。此外因為傳統式溶液配製法所製備之催化奈米金屬顆粒較大，與之相比快速熱蒸鍍法(Rapid Thermal Evaporation, RTE)所製備之催化金屬奈米顆粒就小非常多，因此我們也使用快速熱蒸鍍法沉積催化金屬奈米顆粒於三氧化鎢感測薄膜表面。而如先前研究所知，較小顆粒之催化金屬顆粒有利於增加感測元件的有效比較面積，藉此提升感測性能與速度。另一方面因感測元件於感測時常常產生巨量冗餘資料，導致元件於物聯網應用時會降低傳輸速度並使硬體需求提高。為克服此問題本論文提出以一階微分與卡爾曼濾波減點演算法應用於本論文所提之元件，成功且有效濾除大量冗餘資料，並將減點後之數據以保型分段三次內插法還原以供後端特性分析使用。實驗結果顯示，補點後之數據與原始數據非常相似，故該方法可有效應用於氣體感測元件。此外本論文不僅探討各元件對於不同感測氣體之相關感測電性、偵測效能和動態表現外，更利用熱離子發射方程式描述感測器於不同待測氣體環境下之電壓-電流特性，藉由此公式，本論文在蕭特基二極體方面可求得蕭特基位障之變化、熱力分析，而在化學電阻式之半導體金屬氧化物感測器方面可分析得知其待測氣體於元件的表面覆蓋率、熱力分析與經驗公式等。藉此建立本論文所提感測元件之感測特性與響應時間。

In this dissertation, a series of III-V nitride compound material-based and semiconductor metal-oxide-based chemical gas sensor of Schottky diode and chemiresistive (resistor) type are fabricated and studied. These materials consist of AlGaN/GaN-based Schotty diode and tungsten trioxide (WO3)-based chemiresistive (resisitor) type. Both are decorated on the surface of sensing area with nanoparticles of catalytic metal. In this dissertation, the high-density two-dimensional electron gas is easily formed near the interface of AlGaN/GaN heterostructure. It is known that a variation in the effective Schottky barrier will result in the gas sensing current change. Therefore, the magnitude of 2DEG is modulated by the various in the effective Schottky barrier height due to dipole layer variation. Based on this mechanism, the AlGaN/GaN-based gas sensor is very sensitive to gas concentration variation. In addition, the WO3-based chemiresistive (resistor)-type gas sensor has attracted considerable attention recently, for its relatively wide bandgap of 2.6 ~ 2.7 eV and high diffusion oxygen vacancy coefficient as well as its thermal and chemical stability. The wide bandgap will make the depletion region significantly decreased and thus leads to resistance variation on introducing the target gas. Moreover, the rapid thermal evaporation (RTE) has been employed to evaporate smaller-size Pt nanoparticles. Based on previous research, the catalytic ability and surface area/volume ratio (SA/V) usually affects sensing properties. Compared with grain size of Pt NPs from traditional drop-coating approach, the RTE approach has smaller grain size than drop-coating approach.
On the other hand, gas sensors play a vital role in the Internet of Things (IoT) applications. Generally, sensors usually generate large amounts of data with a great deal of redundant data among them. During sensing work, the wireless transmission rate will be slowed down by these redundant data. To overcome this issue, the first order differential (FOD) and Kalman filter algorithm has been employed to filter and delete the redundant data. Thus, these processed data can be more smoothly transmitted to the data processing center. In addition, the shape-preserving piecewise cubic interpolation (SPPCI) algorithm is employed to recover these transferred data at the data processing center. After SPPCI approach processing, the recovery data are very close to original data. Processing the sensing data through these two algorithms can reduce the amount of data and improve the transmission efficiency. As a result, the SPPCI algorithm can effectively filter and delete redundant data, and the FOD algorithm can restore restored data and retain its sensing feature.
In this dissertation, upon exposing different gas concentration, the detailed performances for each study device are completely studied, including characteristics of current-voltage curve, transient curve response, response (recovery) time. In addition, based on the thermionic emission model, the current-voltage characteristic and sensing behavior are analyzed for Schottky diode and chemiresistive (resistor)-type gas sensor under introduction of the target gas. Besides, the sensing characteristics of Schottky diode type gas sensors are calculated from Schottky barrier height variation, thermodynamic and explores the chemical sensing (resistance) type gas sensing behavior with the thermodynamics, and experience rule.

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