本論文中首先提出利用準分子雷射退火(excimer laser annealing, ELA)在玻璃基板上成長低溫多晶矽薄膜(LTPS)，利用此LTPS薄膜及金屬氧化層研製蕭特基二極體式一氧化碳感測器。並分析不同金屬氧化層對蕭特基二極體的一氧化碳感測特性影響。金屬氧化層與電極傳來的電子形成帶負電的氧離子。當一氧化碳氣體與氧離子接觸時就會產生二氧化碳並釋放出電子到低溫多晶矽層，因而降低能障高度及增加感測電流。在不同的氧化層中，二氧化錫(tin oxide, SnO2)具有較寬的能隙 (3.9eV)，故進入SnO2的電子不易再回到電極，因此具有較高的反應機率。在100 ppm的一氧化碳氣體濃度下，感測比值(relative sensitivity ratio)可高達546%。吾人藉由平衡常數、反應熱探討操作溫度對一氧化碳感測器的影響。發現高溫條件下的二極體會有較佳感測能力，並由實驗結果證實這種趨勢。
為了提高感測比值，吾人利用水熱法(hydrothermal method)製備各種奈米結構的金屬氧化層 如奈米花(nano flower)、奈米微粒(nano particle)、奈米孔洞(nano pore)及奈米柱(nano rod)以增加其反應表面積／體積比。實驗結果證實具奈米結構感測層之二極體的確具有較佳的感測能力。尤其奈米花結構其感測比值更可高達983%，為平面薄膜結構之1.8倍。高出已發表之電阻式一氧化碳感測器近10倍。
另外，本研究更研發各種整體奈米結構(whole nano structure)的p-i-n二極體式感測器。利用特殊化學溶液，將p型矽(100)基板先蝕刻出矽奈米尖端(nano tip)或奈米柱狀結構，再於其上沉積p-i-n薄膜及完成感測元件。藉著整體的奈米結構得以更進一步提升反應表面積／體積比。再利用鑽石及碳化矽半導體薄膜之高能隙特質，來降低二極體漏電流大小提高感測比值。結果鑽石與碳化矽奈米柱狀元件感測比值分別提高到270%和180%。
於本論文中，吾人更對奈米結構提升蕭特基及p-i-n二極體感測一氧化碳機制做深入的研究。並以能帶模型詳述在空氣與一氧化碳環境下電子傳導機制之異同。

In this dissertation, for the first time, the Au/MO/n-LTPS MOS Schottky diodes on a glass substrate were developed for carbon monoxide (CO) gas sensing applications. The MO is metal oxide including SnO2, ZnO and TiO2, and utilized as the sensing element. To enhance sensing ability by enlarging the surface to volume ratio, the MO was formed in nano structure. Various nano structures such as nano flower, nano particle, nano pore and nano rod were prepared with hydrothermal methods for different MO materials. The effects of the nano structures on the device’s performances were studied and compared. For SnO2, experimental results show the nano structure sensors have a better performance than that without the nano structures, especially for the nano flower structure has a sensitivity of 983%, which is ~1.8 times higher than the thin film one, or ~9.8 times over the reported resistance type sensor.
Besides, the aqueous chemical method was also applied to prepare the high performance p-i-n diode type whole nano structure CO sensors. The diode was formed on the Si substrates, which had preferentially etched to form nano tip or nano rod depending on the etching solution. On the other hand, used high band gap semiconductor such as diamond or SiC material as i layer to suppress the off current in air, and thus promoting the sensitivity. Consequently, the whole nano rod n-SnOx/i-diamond/p-diamond and n-SnOx/i-SiC/p-SiC p-i-n diode on p-silicon substrate can achieve the high sensitivity up to 270% and 180%, respectively.
The enhancements with the nano structures in both type sensors are interpreted in details with models and band diagrams.

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