利用化學氣相沉積法成長之大面積單晶石墨烯及其在電晶體之應用

Abstract

本論文以化學氣相沉積法在銅箔上成長大面積且單晶的石墨烯，利用簡便無汙染的氣泡轉移法，將石墨烯轉印至目標基板上，製作成石墨烯場效電晶體。石墨烯場效電晶體容易受到製程的汙染與環境的影響，使得量測結果出現明顯的遲滯現象，利用高溫退火並塗佈自組裝分子六甲基二矽氮烷 (HMDS)，去除易摻雜石墨烯之極性水分子與轉移過程中的污染源並防止環境再次對石墨烯通道造成影響，進而降低遲滯現象並提升元件穩定性與壽命。雖然單晶石墨烯場效電晶體具有極高載子遷移率，但是石墨烯屬零能隙半導體和低電流開關比的特性將限制其在邏輯電路上的應用。因此，透過以原子力顯微鏡之區域陽極氧化製備的雙切痕石墨烯場效電晶體，在雙切痕間距小於一百奈米時，將能觀察到其能隙開啟的現象。雖然以目前的結果仍有待商榷，不過，以雙切痕製作線寬小於一百奈米之石墨烯場效電晶體仍是極具潛力的應用。

In this thesis, single-crystal graphene films are prepared by using chemical vapor depositions on copper foils. The prepared graphene films in millimeter sizes are then bubbling transferred to silicon-dioxide/silicon substrates for transistor fabrications. After high-temperature annealing and hexamethyl-disilazane passivation, the water attachment is removed from the graphene channel. The elimination of uncontrolled doping and enhancement of carrier mobility accompanied by these procedures indicate that they are promising for fabrications of graphene transistors. Although the single-crystal graphene field-effect transistors (FETs) are demonstrated with high carrier mobility values, the zero bandgap nature of graphene would still limit the devices’ application in logic circuits due to its low ON/OFF ratios. Therefore, by using dual-cut transistor architecture to transfer the channel region to within the two cuts and atomic force microscopy local anodic oxidation, the phenomenon of bandgap opening is observed for the devices with < 100 nm cut separation. Although the bandgap opening phenomenon is not completely confirmed based on current results, the dual-cut device architecture for graphene transistors with < 100 nm channel widths is still very promising for practical applications.