石墨烯為一新興二維碳材料，擁有較矽良好之導電性質，而室溫下具備高電子遷移率，使其多應用於場效電晶體之製作。以電子做為傳輸之N型電晶體的效能較P型佳，因此本實驗以N型材料為電晶體的通道。由於空氣中的水氣及氧原子吸附，造成石墨烯多為P型，在此以氮氣電漿摻雜和通入氨氣於化學氣相沉積系統 (CVD)，利用與碳原子相近之大小，且有五個價電子之氮摻入石墨烯表面，進而改變石墨烯結構和電性。氮氣電漿在石墨烯表面造成缺陷，隨處理時間增加，氧和缺陷鍵結使碳成分減少，電晶體量測結果顯示石墨烯通道為P型，電子遷移率也隨處理時間增長而下降。藉由不同偏壓，氨氣在CVD成長石墨烯之摻雜效果亦不同。加正偏壓時，Dirac point從+15 V向左位移至+5 V；加負偏壓時，Dirac point更移動至-10 V，證明此石墨烯經由摻雜後轉變為N型材料，其中碳氮鍵結的pyridinic和quaternary型態，是造成N型摻雜的主要原因。比較兩種氮摻雜方式，氮電漿處理雖較直接，但電漿造成之缺陷會與空氣中的氧結合，而直接在石墨烯成長時通入氨氣，能使碳氮鍵結機會增加，使石墨烯轉為N型。

Graphene, a two-dimensional material with hexagonal arrangement in carbon atoms, has promising characteristics such as good conductivity and high carrier mobility in room temperature that has widely applied in fabrication of field effect transistor (FET). To enhance the transport properties of FET, n-type material is used as conductive channel due to its majority carriers, electrons. However, the synthesized graphene is usually p-type because of adsorption of oxygen in air. For FET applications, pristine graphene is doped with nitrogen atoms which have similar atomic size with carbon and five valence electrons. There are two doping method used in the thesis: nitrogen plasma treatment and direct synthesis of chemical vapor deposition (CVD) with ammonia (NH3) introduction. Prolonged nitrogen plasma treatment creates disorder in graphene structure and oxygen-containing groups react with defects, causing reduction in carbon content and increase in oxygen content. The transfer characteristic of nitrogen-doped graphene by plasma treatment shows p-type behavior as the mobility decreases with treatment time. Synthesis of nitrogen-doped graphene by CVD technique with NH3 introduction has different doping effect with applied bias, ±10 V. The Dirac point shifts from +15 V to +5 V after applying bias, +10 V. Furthermore, the Dirac point shifts to -10 V under bias -10 V, which indicates the n-type behavior. In addition, the pyridinic and quaternary N of C-N bond is dominant for effective doping in this method. Although the plasma treatment is a simple way to introduce heteratoms, CVD technique is a direct synthesis in doping atoms during growth. Defects created by plasma treatment would coordinate with oxygen while direct doping would increase the possibility in bonding with carbon and nitrogen atoms which leads to effective nitrogen doping.

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