在本論文中，我們研製一系列高性能三-五氮族與半導體性金屬氧化物　之化學感測器，包含蕭特基二極體、電阻式元件及延伸式閘極場效電晶體。三-五氮族化合物半導體材料如: 氮化鋁鎵及氮化鎵系列材料，可用來當作感測平台。由於三-五氮族化合物半導體具有比矽材料較寬之能隙，因此，使用其製作而得之元件可適用於高溫環境之應用。此外，鉑和鈀分別對氨氣和氫氣具有良好的觸媒活性，可用來當作感測金屬。另一方面，半導體性金屬氧化物材料如: 氧化鎳及氧化鋅，前者對於酸鹼值及特定氣體具有良好的感測反應，並擁有極佳的化學穩定性及抗腐蝕性，極適合用來作為酸鹼值及氣體之感測薄膜；後者則對於二氧化氮氣體具有極佳的感測特性，適合用於特殊氣體感測用途。除了探討這些半導體式氣體感測器在不同溫度下對不同濃度的氣體之相關感測電性、偵測效能和動態表現，也深入研究氧化鎳酸鹼值感測器之感測效能及非理想效應。
首先， 我們以化學式無電鍍法製備鉑/氮化鋁鎵/氮化鎵蕭特基二極體式氨氣感測器。我們利用熱離子發射方程式描述感測器於氨氣環境下之電壓-電流特性，並且經由該方程式求得二極體之蕭特基位障高，可以觀察到會隨著不同濃度之氨氣而改變。我們從感測器之二極體參數、感測響應、響應時間方面探討元件之氨氣感測行為。
其次，研究具奈米結構之鈀/氮化鋁鎵/氮化鎵蕭特基二極體之氫氣感測特性。首先，第一種結構利用塗佈二氧化矽奈米粒子於鈀感測層與氮化鋁鎵之間，以形成鈀/二氧化矽/氮化鋁鎵(金屬/氧化物/半導體)的氫氣感測器，不僅可防止鈀與氮化鋁鎵間的相互擴散，獲得一個品質較佳的金半界面，也藉由二氧化矽奈米粒子獲得較大的比表面積，使得氣體感測特性大幅提升。另一方面，我們成功將聚苯乙烯奈米球以蒸鍍舉離方式製備出角錐形之鈀奈米結構，此一結構可有效增加感測層之比表面積，而氣體吸附座也會隨之增加。並在不同氫氣濃度與溫度環境下，分析兩種類型感測器之氫氣感測行為。
接著，研製氧化鎳薄膜延伸式閘極場效電晶體式酸鹼值感測器與電阻式氣體感測器。將延伸式閘極感測元件置於不同酸鹼值之磷酸緩衝溶液中，藉由感測元件之三端電流-電壓特性曲線變化，以探討各種濺鍍參數與後退火對感測特性之影響。此外，我們將氧化鎳薄膜沉積於指叉式電極上，以製備電阻式氣體感測器，探討並分析在不同溫度下感測元件之氫氣與氨氣感測行為。
最後， 探討以氧化鋅奈米粒子研製電阻式氣體感測器對二氧化氮之感測特性。利用氧化鋅奈米粒子提升感測元件的比表面積，進一步使得氣體吸附座增加，因此，元件之氣體感測特性有效地改善。由實驗結果得知，該元件在高溫環境下，不但對於高濃度二氧化氮具有極佳的感測靈敏度，也可偵測到極低濃度的二氧化氮。由於本論文所研製之元件呈現良好之感測效能，且製程方式與微機電系統製程相容，因此，本研究之感測元件在高效能感測器與微機電系統整合方面極具潛力。

In this dissertation, a series of high performance　III-V nitride compound and semiconducting metal-oxide based chemical sensors, including Schottky diodes, resistors, and extended-gate field-effect transistors (EGFETs), are fabricated and studied. III-V nitride compound semiconductors, such as AlGaN- and GaN-based materials, serve as sensing platforms. Since these materials have larger band gaps, the fabricated devices are suitable for high-temperature operation. In addition, Pt and Pd are used as sensing metals because of their good catalytic activity toward ammonia and hydrogen gases, respectively. On the other hand, metal-oxide semiconductor, such as NiO- and ZnO- based materials, serve as a sensing membrane. The NiO sensing membrane demonstrates excellent pH sensing and specific gas sensing characteristics, good chemical stability, and corrosion resistance. The ZnO sensing membrane shows excellent performance for NO2 sensing. Therefore, the NiO-based material is suitable for high-performance pH sensing applications, and both NiO- and ZnO-based materials can be used as specific gas sensing membranes. Electrical characteristics and sensing performance of the studied gas sensors are investigated at different temperatures and gas concentrations. Furthermore, pH sensing properties and non-ideal effects of the studied NiO-based pH sensor are studied.
First, a chemically electroless plated (EP) Pt/AlGaN/GaN Schottky diode-type ammonia sensor is fabricated and studied. The thermionic emission (TE) equation is employed to characterize the current-voltage (I-V) behaviors of the studied EP device upon introduction of ammonia gases. The Schottky barrier height extracted from the TE equation is found to be sensitive to ammonia gases under various concentrations. Ammonia sensing behaviors of the studied EP device are investigated in terms of those diode parameters, sensing responses, and response times.
Second, the hydrogen sensing characteristics of Pd/AlGaN/GaN Schottky diodes with nanostructures are investigated. Pd/SiO2/AlGaN (metal/oxide/semiconductor) hydrogen sensors, prepared by spin-coating SiO2 nanoparticles between Pd and AlGaN layers, are fabricated. Due to the observation of a better junction quality and a higher surface roughness, hydrogen sensing properties of the studied device can be improved. On the other hand, a Pd pyramid-like nanostructure is successfully made by thermal evaporation and lift-off processes with PS nanospheres. This structure can efficiently increase the surface-area-to-volume ratio which caused the more active adsorbing sites. Analyses of the sensing properties of the studied devices with nanostructures at different temperatures and hydrogen concentrations are presented, respectively.
Third, NiO thin film-based extended-gate field-effect transistor (EGFET)-type pH sensors and a resistor-type gas sensor, prepared by the radio-frequency (RF) sputtering process, are fabricated and studied. The influences of various sputtering conditions and post-annealing are investigated by I-V curves variation of studied EGFET-type devices when immersing in different pH buffer solutions. Moreover, a NiO thin film-based resistor-type gas sensor, deposited on interdigitated electrodes, is fabricated. Hydrogen and ammonia sensing behaviors of the studied resistor-type device are analyzed and investigated at different temperatures.
Finally, the nitride oxide (NO2) sensing performance of ZnO nanoparticles (NPs)-based sensors is demonstrated and investigated. ZnO NPs are employed to the increase surface-area-to-volume ratio of the studied device which causes more active adsorbed sites. Thus, an enhanced sensing performance can be observed. Experimentally, the studied devices exhibits excellent sensing responses towards high NO2 concentration and a low detection limit at high temperatures. Based on good results and compatibility of these sensing devices in this dissertation, the studied devices are promising for the integration of high-performance sensor and micro-electro-mechanical-systems (MEMS).

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