本論文主要分成兩部分，第一部分以化學氣相沉積法(Chemical Vapor Deposition)合成大面積的單層二硫化鉬，藉由控制製程參數獲得高品質單層二硫化鉬。第二部分製備二硫化鉬之場效電晶體(FET)，藉由電性量測與光感測(Photodetection)量測，探討單層二硫化鉬之光電特性及光感測器應用，二硫化鉬之場效電晶體元件具有優異之電性：開關電流比(On off current ratio)可達104至105，載子遷移率約為12.5cm2/Vs。單層二硫化鉬具有優異的光感測特性，其場效電晶體元件照光後，光電流於7.6秒內能增加70%飽和光電流，25秒內能降低70%飽和光電流，經由計算可以得知在汲極電壓為1V且閘極電壓為10.5V下，光響應率高達392.5A/W。另外從實驗結果可以得知在大氣下的量測較能使得光電流有弛豫(Relaxation)的現象，可能的原因推測是空氣中有一些吸附物會吸附在二硫化鉬的表面，這些吸附物傾向於捕獲二硫化鉬內部的本質電子，造成表面類似p型摻雜的結果，也就是如D+e-→D-的反應式，而在照光後激發電子電洞對，其中的電洞與帶負電的吸附物進行復合(Recombination)，也就是這些吸附物在照光後有類似光脫附(Photo-desorption)的效果，寫成反應式即D-+h+→D，因此在大氣中關閉光源時，由於這些吸附物傾向於捕獲電子，產生類似協助光電流進行弛豫(Relaxation)的效果，而在照光時，這些吸附物與電洞複合進而脫附離開材料表面，反之在真空中，因為缺乏這些吸附物，在關閉光源時無法有效將光電流弛豫，所以在關閉光源時汲極電流下降的較在大氣中慢，而在打開光源時，也因為不需要提供電子電洞對復合這些帶電的吸附物，因此可以得到較高的光電流值。

In this research, we used chemical vapor deposition to synthesize large area monolayer MoS2, then we fabricated MoS2 FET and measured its electrical properties and photodetection.
MoS2 has excellent electrical properties: our device could reach 12.5 cm2/Vs mobility, 104 to 105 on/off current ratio.
In photodetection of MoS2 FET, our device took 7.6 second to reach 70% of saturation photocurrent, 25 second to decay. And under 1V drain voltage, 10.5V gate voltage, the responsivity of our device was 392.55A/W.

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