標題: 二維晶體異質結構在光偵測器與電晶體之應用
The Applications of Two-Dimensional Crystal Hetero-Structures for Photodetectors and Transisters
作者: 廖崑成
陳怡君
林時彥
Liao, Kun-Cheng
Chen, Yi-Chun
Lin, Shih-Yen
影像與生醫光電研究所
關鍵字: 二維材料;異質結構;石墨烯;二硫化鉬;Two-Dimensional Crystal;Hetero-Structures;Graphene;MoS2
公開日期: 2016
摘要: 本論文以化學氣相沉積法在藍寶石基板成長石墨烯與二硫化鉬薄膜,利用溫度750 oC、800 oC、850 oC、900 oC,且同時放入足量的硫粉將二硫化鉬薄膜再硫化,提升二硫化鉬薄膜品質,透過材料分析儀器檢測再硫化後的薄膜,得出溫度850 oC再硫化為最理想條件,進一步的製備出二硫化鉬/石墨烯異質結構電晶體,發現再硫化異質結構元件隨照光有巨大的狄拉克點位移,相比未再硫化的異質結構元件,其位移有大幅的提升,說明再硫化的步驟,使二硫化鉬薄膜在照光的狀況下有更多的光電子產生,並轉移至低電阻性的石墨烯,造成類似於N型參雜的現象。另外,將石墨烯薄膜作為電極與鈦/金作為電極做比較,先利用TLM模型得到石墨烯相較於鈦/金具有較小的接觸電阻,進而製作出二硫化鉬電晶體,首先在背閘極電晶體製程中,由於轉印過程較為繁雜,不可避免會出現製程汙染和光阻殘留,無法突顯出以石墨烯作為電極之優點,改善製程進一步製備出上閘極電晶體,發現石墨烯作為電極其載子遷移率高達0.251 cm2/V-1s-1,而元件電流開關比為2371.98,以金屬作為電極其載子遷移率達0.0074 cm2/V-1s-1,而元件電流開關比為113.05,說明較小的接觸電阻確實可提升元件特性,未來若發展其它二維材料可與石墨烯電極做結合,將有助於提升二維材料電晶體特性。
Enhanced photoluminescence intensities are observed for the MoS2 film prepared by chemical vapor deposition (CVD) with an additional 850 oC post-growth annealing procedure under sulfur-rich environment. The enlarged Dirac point shift of the MoS2/graphene hetero-structure photodetectors with the post-growth annealing procedure suggests that more photo-excited electrons will transport to the graphene and effectively higher n-type doped the channel. The direct 2-D crystal hetero-structure growth by using CVD has avoided the complicated procedure of sequential attachment of different 2-D crystals, which is advantageous for practical applications. For electronic device applications, we have compared graphene and Ti/Au as electrodes for MoS2 transistors. TLM model has been used to obtain the contact resistance for the two electrodes. The resistance value of graphene is much less than Ti/Au. In order to compare the impact from the two electrodes, we used them to do S/D contact to fabricate MoS2 top-gated transistor. The carrier mobility values for transistors with graphene and Ti/Au as electrodes are 0.251 cm2/V-1s-1 and 0.0074 cm2/V-1s-1, respectively. A lower contact resistance is helpful for current flows in transistors. The technique of using graphene as the electrode will help to improve the device performances for devices based on 2-D materials.
URI: http://etd.lib.nctu.edu.tw/cdrfb3/record/nctu/#GT070358234
http://hdl.handle.net/11536/138386
Appears in Collections:Thesis