臺灣博碩士論文加值系統

層狀二維(Two-dimensional, 2D)過渡金屬硫族化合物(Transition Metal Dichalcogenides, TMDCs)之所以受到關注是因為其層與層的三明治結構，可簡易的薄化厚度並同時具有直接能隙性質，層與層之間僅靠微弱的凡得瓦力(van der Waals Force, vdW)鍵結，相較於石墨烯(Graphene)，層狀二維過渡金屬硫族化合物具有半導體及金屬性質，透過減少厚度至單層，其半導體性質能隙可由間接能隙改變為直接能隙，此特殊性質具有很大的應用潛力，被視為下一世代半導體產業的新興材料。
本論文利用化學氣相傳導法(Chemical Vapor Transport, CVT)並加入傳導劑碘(I2)或溴(Br2)成長MoSxSe2-x(2≤x≤0)三元合金。利用掃描電子顯微鏡(Scanning Electron Microscope, SEM)及能量散射光譜分析儀(Energy Dispersive X-Ray Spectrometer, EDX)確認樣品元素比例及其表面樣貌。在光學量測方面，採用壓電調制反射光譜(Piezoreflectance, PzR)技術量測溫度於295 K至25 K激子躍遷訊號A及B的能量，分析激子躍遷訊號與成分之間的變化，以Varshni方程式探討激子躍遷訊號與溫度的相依性，獲得Varshni參數再與成分關係進行討論，分析其溫度相依相關參數隨硫成分變化，呈現出遞增的二次方曲線(Parabolic)變化。最後，不同硫成分的激子躍遷訊號隨溫度變化之情形可藉由修正的Varshni方程式來描述。

Two-dimensional transition metal chalcogenides (TMDCs) have attracted attention because of their layer-to-layer sandwich structure. This structure can be easily fabricated in atomic scale thickness. The layer is bonded by weak Van der Waals Force (vdW). Compare to graphene, TMDCs have both semiconductor and metal properties. The band gap can be changed from an indirect energy gap to a direct energy gap by varying the thickness from bulk to monolayer. The unique optoelectronic properties have great potential for the applications in next generation semiconductor industry.
In this study, the chemical vapor transport (CVT) is used to add the conductive agent iodine (I2) or bromine (Br2) to grow the MoSxSe2-x(2≤x≤0) ternary alloy. The composition and its surface morphology were confirmed by scanning electron microscope and energy dispersive X-ray spectrometer. In optical measurement, piezoreflectance (PzR) spectroscopy technology was used to measure the exciton transition energies. The PzR spectroscopy has been employed to study the temperature and compositional dependence of the excitonic transition energy of MoSxSe2-x alloys in the temperature range from 25 to 295 K. Their temperature dependences were analyzed using Varshni semi-empirical expressions. It is found that the values of Varshni coefficients obtained from MoSxSe2-x varied with bowing effects with increases sulfur composition. Based on the experimental results, the temperature and compositional dependence of excitonic transition energy of MoSxSe2-x alloys has been empirically deduced for the entire alloy range in this study.

目錄
明志科技大學碩士學位論文指導教授推薦書 i
明志科技大學碩士學位論文口試委員會審定書 ii
致謝 iii
摘要 iv
Abstract v
目錄 vi
圖目錄 viii
表目錄 x
第一章 緒論 1
1.1 前言 1
第二章 晶體成長 6
2.1 晶體成長方法 6
2.2 單晶成長之設備 8
2.2.1 晶體成長反應系統 8
2.2.2 真空系統 10
2.3 晶體成長 12
第三章 量測技術與原理 14
3.1 掃描電子顯微鏡(SEM) 14
3.1.1 SEM發展 14
3.1.2 SEM原理 15
3.2 能量散射光譜分析儀(EDX) 18
3.3 調制光譜(Modulation Spectroscopy) 20
3.3.1 調制光譜簡介 20
3.3.2 壓電調制反射光譜(PzR) 23
第四章 實驗結果與討論 29
4.1 MoSxSe2-x的變溫壓電調制反射光譜 29
4.2 MoSxSe2-x溫度相依參數分析 36
4.3 MoSxSe2-x溫度相依能隙分析 43
第五章 結論 47
參考文獻 48


圖目錄
圖1-1 元素週期表中常見二维材料的分佈圖。 4
圖1-2 石墨烯優點。 4
圖1-3 2H-TMDCs原子結構圖。 5
圖2-1 影響單晶成長及品質之條件。 7
圖2-2 三區域控溫高溫爐示意圖。 8
圖2-3 晶體成長溫度之管內實際溫度梯度圖。 9
圖2-4 晶體成長系統示意圖。 9
圖2-5 長晶真空系統構造圖。 11
圖2-6 石英管示意圖。 13
圖2-7 晶體成長流程圖。 13
圖3-1 掃描式電子顯微鏡(Phenom ProX)。 16
圖3-2 掃描式電子顯微鏡示意圖。 17
圖3-3 電子束與樣品作用所產生之訊號。 17
圖3-4 EDX光電子產生示意圖。 19
圖3-5 EDX產生之光譜圖。 19
圖3-6 壓電調制反射光譜樣品製備圖。 25
圖3-7 高壓放大器(TReK 609E-6)。 26
圖3-8 壓電調制反射光譜量測系統圖。 26
圖3-9 碘鎢燈之光譜分佈圖。 27
圖3-10 鎖相放大器(EG&G 7265)。 27
圖3-11 真空系統(Pfeiffer Vacuum TSH 071)。 28
圖3-12 壓縮機(CTI CRYOGENICS 8200 Compressor)。 28
圖4-1 MoS2的能帶結構圖。 30
圖4-2(a) MoSe2壓電調制反射光譜圖。 31
圖4-2(b) MoS0.6Se1.4壓電調制反射光譜圖。 32
圖4-2(c) MoSSe壓電調制反射光譜圖。 33
圖4-2(d) MoS1.4Se0.6壓電調制反射光譜圖。 34
圖4-2(e) MoS2壓電調制反射光譜圖。 35
圖4-3(a) MoSe2激子躍遷訊號對溫度變化以Varshni方程式擬合曲線。 37
圖4-3(b) MoS0.6Se1.4激子躍遷訊號對溫度變化以Varshni方程式擬合曲線。 38
圖4-3(c) MoSSe激子躍遷訊號對溫度變化以Varshni方程式擬合曲線。 39
圖4-3(d) MoS1.4Se0.6激子躍遷訊號對溫度變化以Varshni方程式擬合曲線。 40
圖4-3(e) MoS2激子躍遷訊號對溫度變化以Varshni方程式擬合曲線。 41
圖4-4(a) Varshni參數-α與MoSxSe2-x成分相依性。 44
圖4-4(b) Varshni參數-β與MoSxSe2-x成分相依性。 45


表目錄
表1-1 具有單層二維材料特性總表。 3
表4-2 MoSxSe2-x以Varshni方程式擬合得到的溫度相依性相關參數。 42
表4-2 Varshni參數α及β與溫度相依性擬合得到的曲率參數。 46

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