使用石墨烯電極之高性能二硫化鉬薄膜電晶體

本論文先詳細的介紹石墨稀、二硫化鉬異質結構的製備方式，並使用紫外光電子能譜儀量測兩種二維材料的能帶。之後使用機械剝離法分離出擁有奈米級厚度的二硫化鉬並製作出薄膜電晶體，利用光學顯微鏡及原子力顯微鏡的搭配篩選出較佳厚度範圍的二硫化鉬，並利用低功函數金屬鉻以及石墨稀當作電極來達成歐姆接觸。接著我們比較兩種電極，發現使用石墨稀電極之二硫化鉬薄膜電晶體擁有較好的場效電子遷移率、電流開關比以及次臨界擺幅。接著我們量測石墨烯之特性曲線，發現不同於一般金屬，其電流會隨著閘極電壓呈n型、p型，表示其功函數會隨著閘極電壓而改變，因此能使二硫化鉬薄膜電晶體呈現出更好的電性。為了更進一步提升場效電子遷移率，我們使用石墨稀電極先製，之後再疊上二硫化鉬的方法，此方法可以避免聚甲基丙烯酸甲酯的殘留，也可以避免二硫化鉬經高溫製成後氧化。使用此方法所製作的二硫化鉬薄膜電晶體電流開關比可達到6×10^6的數量級，場效電子遷移率可以達到約116 cm2/V-sec，次臨界擺幅可以降低至0.515V/dec。

關鍵字

二硫化鉬薄膜電晶體；石墨烯電極；可調變之功函數；聚甲基丙烯酸甲酯殘留

並列摘要

In this thesis, we detail the heterostructure fabrication system, and measure band diagram of MoS2 and graphene by using ultraviolate photoemission spectroscopy. And then the mechanically exfoliated 2D material MoS2 nanosheet was used to fabricate thin film transistor and their electrical properties were investigated as well. By checking their thickness by optical microscopy and atomic force microscopy, the nanosheet with an appropriate thickness can be selected. It was found that the ohmic contact on MoS2 can be achieved by low work function metal Chromium and graphene. Afterwards, we compare these two kind of contact. It was found that thin film transistor using graphene contact has better performances in field effect mobility, on/off ration, and subthreshold swing. Different from metal contacts, the work function of graphene can be modulated, so graphene contact TFT can achieve better performance than Cr/Au contact TFT. To further improve the performance of MoS2 TFT, a new method using graphene contact first and MoS2 layer last process that can avoid polymer residue and high processing temperature is performed. MoS2 TFT using this method shows on/off current ratio up to 6×10^6 order of magnitude, the mobility is 116 cm2/V-sec, and subthreshold swing is only 0.515 V/dec.

並列關鍵字

molybdenum disulfide (MoS2) thin film transistor ； graphene electrode ； modulated work function ； PMMA residues

參考文獻

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國際替代計量

使用石墨烯電極之高性能二硫化鉬薄膜電晶體

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