臺灣博碩士論文加值系統

本研究主要探討一維硫化鎘奈米線與二維二碲化鉬薄片形成的n-p接面結構檢測與特性分析。首先，透過水平式三區真空爐管合成鎵摻雜的硫化鎘奈米線，XRD分析可以確認成長出的是wurzite結構的硫化鎘。XPS分析確認鎵元素具有4.92 %的摻雜比例。PL光譜量測中也能觀察到因鎵摻雜而使硫化鎘的發光波長產生紅移的現象，同時波形也會發生因雜質添加造成半高寬增加的情況。在元件表現方面，鎵的摻雜提供了額外的載子使硫化鎘導電性不佳的缺點大幅改善，並且可達105左右的開關比，透過計算與統計後可以得到平均載子遷移率125.4 cm2/Vs與平均載子濃度2.26×1017 cm-3。另一方面，利用氧電漿和烘烤輔助下以機械剝離的方式獲得少數層數的二碲化鉬薄片，藉由拉曼光譜中A1g及E12g的峰值差與E12g及B12g的峰值比能夠針對二碲化鉬的層數進行檢測。之後，將成長的鎵摻雜硫化鎘奈米線與二碲化鉬以光學微影製成n-p異質結構元件並對其進行光電特性的探討，異質結構元件呈現典型的整流特性，接著在不同強度的照光發現此元件的電流隨著光強度增大而上升，同時元件也有著穩定的光響應特性，透過異質結構的能帶圖可說明此元件在正偏壓時以多數載子的擴散來產生光電流，逆偏壓時，由於多數載子的缺乏而轉向為少數載子的穿隧來形成逆向電流。最後，利用單一波長的光對元件照射並進行光伏效應探討，在波長520 nm的綠光照射下，此異質結構元件能夠得到0.388 V的開路電壓，2.86 pA的短路電流以及5.14 %的轉換效率。

In this study, we investigated the structures, the physical properties and optoelectronic properties of Ga-doped cadmium sulfide (CdS) nanowire (NW) and molybdenum ditelluride (MoTe2) flake n-p heterostructure.
First, we synthesized Ga-doped CdS NWs via chemical vapor deposition (CVD) method and X-ray photoelectron spectroscopy (XPS) analysis confirmed that Ga has been incorporated into CdS NWs with the atomic percentages of 4.92%. The red-shift and broadened full width at half maximum (FWHM) of the band-edge emission of CdS are due to the Ga dopant in CdS NWs. We then discussed the electrical transport properties of the Ga-doped CdS NWs, the electrical properties showed significant improvement with the comparison of the undoped one, and the on-off ratio is up to 105 for Ga-doped CdS field-effect transistors, gallium dopant serves as donor in CdS NWs with the average mobility 125.4 cm-2/Vs and carrier concentration 2.26×1017 cm-3. On the other hand, few-layered MoTe2 flakes were obtained by modified mechanical exfoliation from bulk, the peak difference of A1g and E12g and the intensity ratios of E12g and B12g in Raman spectra can be used to determine the numbers of layer of MoTe2. Afterward, we fabricated Ga-doped CdS/MoTe2 n-p heterostructure devices by photolithography, and the device showed typical recfication curve. Moreover, the current increased with forward and reverse biases under the increasing power of visible light irradiation, which are attributed to the different mechanisms, the increased current is owing to the diffusion of majority carriers at the interfacial region under forward bias, while is due to the minority carriers tunneled through barrier under reverse bias to form photocurrent due to the lack of majority carriers. Finally, the Ga-doped CdS/MoTe2 n-p heterostructure devices revealed photovoltaic effect with an open-circuit voltage (VOC) of 0.388 V, a short-circuit current (ISC) of 2.86 pA and conversion efficiency of 5.14 % nunder 520 nm light illumination.

摘要 I
Abstract III
致謝 V
目錄 VI
圖目錄 X
表目錄 XV
第一章 緒論與文獻回顧 1
1-1 奈米科技 1
1-2 硫化鎘 (Cadmium sulfide, CdS) 3
1-2-1 硫化鎘的物理特性 3
1-2-2 硫化鎘奈米結構的應用 4
1-2-2-1 金屬氧化物半導體場效電晶體 (MOSFETs) 5
1-2-2-2 太陽能電池 (Solar cells) 7
1-2-2-3 發光二極體 (Light-emitting diodes, LEDs) 9
1-2-2-4 光感測器 (Photosensors) 11
1-3 二碲化鉬 (Molybdenum ditelluride, MoTe2) 13
1-3-1 二碲化鉬的物理特性 13
1-3-2 少數層數二碲化鉬的特性分析 15
1-3-3 少數層數二碲化鉬奈米結構的應用 17
1-3-3-1 雙極性電晶體 (Ambipolar transistors) 18
1-3-3-2 光偵測器 (Photodetectors) 20
1-4 奈米異質結構 21
1-4-1 一維/一維 (1D/1D)異質結構 21
1-4-2 二維/二維 (2D/2D)異質結構 22
1-4-3 一維/二維 (1D/2D)異質結構 24
1-4-3-1 硫化鎘/碲化鎵 (CdS/GaTe) 24
1-4-3-2 氧化銅/二硫化鉬 (CuO/MoS2) 25
1-4-3-3 氮化鎵-二硫化鉬 (GaN-MoS2) 26
1-5 研究動機 27
第二章 實驗步驟 28
2-1 實驗步驟 28
2-1-1 成長鎵摻雜之硫化鎘奈米線 29
2-1-2 以機械剝離法製備少數層數之二碲化鉬 30
2-1-3 異質結構元件製備 31
2-1-4 電性量測 34
2-2 儀器介紹 35
2-2-1 三區真空爐管 (Three-zone furnace) 35
2-2-2 對準曝光機 (Mask aligner) 36
2-2-3 電子束蒸鍍系統 (Electron beam evaporator) 37
2-2-4 電性量測系統 (Electrical property measurement system) 38
2-2-5 掃描式電子顯微鏡 (Scanning electron microscope, SEM) 39
2-2-6 穿透式電子顯微鏡 (Transmission electron microscope, TEM) 40
2-2-7 原子力顯微鏡 (Atomic force microscope, AFM) 41
2-2-8 Χ光繞射儀 (X-ray diffractometer, XRD) 42
2-2-9 Χ射線光電子能譜儀 (X-ray photoelectron spectroscopy, XPS) 43
2-2-10 光致發光光譜儀 (Photoluminescence, PL) 44
2-2-11 顯微拉曼分析儀 (Micro Raman identify spectrometer) 45
第三章 結果與討論 46
3-1 合成鎵摻雜硫化鎘奈米線 46
3-2鎵摻雜硫化鎘奈米線結構分析與檢測 47
3-2-1 掃描式電子顯微鏡分析 47
3-2-2 X光晶體繞射分析 48
3-2-3 穿透式電子顯微鏡分析 49
3-2-4 X射線光電子能譜儀(XPS)分析 51
3-2-5 光致發光(PL)光譜量測 52
3-3 鎵摻雜硫化鎘奈米線場效電晶體元件電性量測 54
3-4 以機械剝離法製備少數層二碲化鉬薄片 58
3-4-1 原子力顯微鏡分析 60
3-4-2 拉曼光譜分析 62
3-4-3 穿透式電子顯微鏡分析 64
3-5 二碲化鉬薄片場效電晶體元件電性量測 66
3-6 一維硫化鎘/二維二碲化鉬異質結構元件電性量測 68
第四章 結論 74
第五章 未來展望 76
參考文獻 77

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