臺灣博碩士論文加值系統

中文摘要
本論文運用化學氣相傳導法成長硫化鍺 (GeS) 晶體,成長溫度為 600°C 且溫度梯度為-2.5°C /cm,維持 14 天後於低溫沉積端慢慢堆疊成長出晶體,最後成功長出 GeS 層狀半導體晶體。
在本研究中,我們利用能量散佈分析儀、X 光繞射儀、拉曼散射、穿透式電子顯微鏡,探討其晶體組成、結構以及結晶晶粒狀況,由上述實驗結果得知硫化鍺莫爾數比為1:1,晶體為正交晶系,它是沿著 [001] 方向生長的層狀半導體,晶格常數分別為a = 4.36 Å 、b =3.67 Å 、c = 10.53 Å 。在光學量測中,利用熱調制反射光譜和穿透光譜分別對樣品進行極化實驗,都可觀測到沿不同晶向極化時,近能隙有兩個躍遷訊號。可藉由極化熱調制反射光譜定義出更精確的躍遷訊號,量測出硫化鍺平行晶向a軸有直接躍遷訊號,為1.620 eV (E0),垂直晶向a軸有一近能隙躍遷約為1.726 eV (E0 ́) ,在後段較高能量的帶間躍遷訊號也能被量測到,範圍從1.6 eV ~5 eV間之極化實驗,分別可以觀測到四個躍遷E0 、E1、E2、E3 (E||a) 和E0 ́、E1 ́、E2 ́、E3 ́ (E⊥a),之後會針對躍遷來源和隨溫度變化關係,來分析和探討。室溫光激發螢光光實驗中,能觀察到平行晶向a軸的自由激子(free exciton,FX) 發光約1.62 eV與熱調制量測之能隙相當,且於低溫10 K,可清楚觀察兩個激子訊號,分別為施子受子對 (donor-accepter pair, DAP)為1.553 eV和FX為1.732 eV,激發螢光實驗結果也表示FX受極化影響,只有在平行晶向a軸可觀測到此訊和熱調制結果一樣。
表面光電壓和光電導量測發現由近能隙開始分別都有一個很寬峰值的電壓和電流的響應,範圍約從1.6 eV~3 eV,之後也針對表面光電壓實驗進行極化測試,確實也獲得的不同的偏極光響應。最後光伏特測試選擇一樣品面積為0.03cm2的硫化鍺晶體,當不照光時~ -3.99mV,照光後光伏輸出可達~ +0.18 V,顯示其為優異之太陽能電池材料。

Abstract
In this work, layered-type GeS crystals were grown by Chemical
Vapor Transport (CVT) method using ICl3 as the transport agent. The required temperature and temperature gradient were set as 600 OC with a gradient of -2.5 OC /cm that could be grown for 14 days to obtain high quality layer crystals .
The crystals were characterized by energy dispersive X-ray spectrometer(EDS), X-raydiffraction (XRD), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED),transmittance, thermorefltance (TR), photoluminescence (PL), surface photovoltage (SPV), photoconductivity (PC) and photovoltaic (PV) experiments.
The layered GeS crystallizes in an orthorhombic structure with an obvious c plane [ (i.e. (001) ]. The lattice constants are a=4.36 Å , b=3.67 Å and c=10.53 Å . From PTR and transmittance results, we found that there are a near-band-edge direct transition along E||a (~1.62 eV) and a transition along E⊥a (~1.726 eV) at room temperature. GeS has four transitions from 1.6 eV to 5 eV obtained by PTR of E||a and E⊥a polarizations.
The PL results show one near-band-edge emission features FX at
1.62 eV detected at 300 K, and the FX is anisotropic and is only seen in the polarization E||a. One additional feature DAP at 1.553 eV has also been detected at 10 K.
The SPV and PC measurements show a long range response from
near-band –edge absorption to 3 eV. The SPV peak is polarization
dependent. PV testing results show a voltage of ~0.18 V generated from a 0.03 cm2 area GeS sample under the illumination of tungsten lamp of 0.22 W/cm2. The result shows GeS a promising candidate of high efficiency solar-cell material.

目錄
中文摘要......................................................... I
Abstract ......................................................III
目錄..............................................................V
第一章 緒論.......................................................1
1.1 硫化鍺材料特性介紹 ............................................2
第二章 硫化鍺之晶體成長............................................4
2.1 長晶程序......................................................4
2.2 成長晶體前樣品配製 ............................................4
2.3 化學氣相傳導法成長 GeS 晶體....................................4
2.4 系統配置......................................................7
2.4.1 高真空系統..................................................7
2.4.2 長晶反應系統................................................8
第三章 量測技術 ...................................................9
3.1 能量散佈分析儀 (EDS) ........................................ 11
3.2 X-ray 晶格繞射分析儀 (XRD) ...................................13
3.3 拉曼散射光譜 (Raman).........................................16
3.4 光穿透光譜 ..................................................19
3.5 調制光譜簡介和系統概論........................................20
3.5.1 熱調制反射光譜量測 (TR).....................................22
3.5.2 樣品製備之方法..............................................22
3.5.3 熱調制光譜實驗的儀器架設流程.................................23
3.6 光激發螢光光譜量測 (PL) ......................................26
3.6.1 光激發螢光光譜原理..........................................26
3.6.2 光激發螢光實驗方法與系統架構.................................28
3.7 表面光電壓光譜量測 (SPV)......................................31
3.7.1 表面光電壓樣品製備..........................................31
3.7.2 表面光電壓實驗的儀器架設流程.................................32
3.8 光電導量測 (PC)..............................................34
3.8.1 光電導原理.................................................34
3.8.2 光電導樣品製作..............................................34
3.8.3 光電導量測實驗及儀器架設流程.................................35
3.9 光伏打實驗...................................................36
3.9.1 光伏打原理.................................................36
3.9.2 光伏打實驗架設流程..........................................36
第四章硫化鍺的實驗結果與討論.......................................38
4.1 晶體結構與組成比例分析........................................38
4.1.1 能量散布分析儀結果分析......................................38
4.1.2 X-ray 繞射儀結果分析........................................39
4.1.3 場發射穿透式電子顯微鏡影像分析 (FETEM) ......................42
4.1.4 拉曼散射結果分析............................................44
4.2 光學實驗分析.................................................46
4.2.1 光穿透光譜結果分析..........................................46
4.2.2 熱調制極化光譜圖結果分析 ....................................47
4.2.3 光激發螢光光譜圖結果分析 ....................................52
4.2.4 表面光電壓光譜圖和光伏打實驗結結果分析........................57
4.2.5 光電導光譜圖結果分析........................................59
第五章 結論......................................................60
參考文獻.........................................................61
圖索引
圖 1. 1 硫化鍺結構圖和晶格面圖 .....................................3
圖 2. 1 簡易長晶程序...............................................4
圖 2. 2 描述密封石英管內,晶體成長機構...............................6
圖 2. 3 硫化鍺晶體圖...............................................6
圖 2. 4 密封石英管所用的真空幫浦系統 ...............................7
圖 2. 5 三區加熱高溫爐系統.........................................8
圖 3. 1 EDS 光電子產生示意圖......................................12
圖 3. 2 EDS 儀器構造圖...........................................12
圖 3. 3 Bragg’s law 反射與晶體平面間之關係.........................13
圖 3. 4 X-ray 繞射儀系統圖........................................15
圖 3. 5 XRD 樣品試片圖 (a)硫化鍺塊材 c 平面 (b) 硫化鍺粉體 .........15
圖 3. 6 Raman 試片圖 ............................................17
圖 3. 7 拉曼光譜儀/微激發螢光光譜儀................................18
圖 3. 8 拉曼光路圖 ..............................................18
圖 3. 9 穿透樣品試片圖............................................19
圖 3. 10 熱調制試片實際完成圖.....................................22
圖 3. 11 TR 量測的系統配置圖......................................25
圖 3. 12 光源經極化片示意圖.......................................25
圖 3. 13 直接能隙與間接能隙半導體躍遷行為示意圖[14].................29
圖 3. 14 (a)電子電洞對的吸收 (b) ~ (f) 半導體中電子-電洞之復合躍遷機制圖...............................................................29
圖 3. 15 光激發螢光光譜量測系統架構圖..............................30
圖 3. 16 表面光電壓樣品示意圖與實際圖..............................31
圖 3. 17 表面光電壓儀器架構示意圖 .................................33
圖 3. 18 光電導樣品示意圖和實際圖 .................................34
圖 3. 19 光導儀器架構示意圖.......................................35
圖 3. 20 光伏實驗樣品.............................................36
圖 3. 21 KEITHLEY 電錶 (a) 照光前電壓 (b) 照光後電壓 ..............37
圖 3. 22 激發光源燈譜全波段.......................................37
圖 4. 1 GeS 強度與游離能的圖......................................38
圖 4. 2 (a) GeS 塊材平面的 X-ray 繞射結果圖 (b) GeS 粉末小單晶的
X-ray 繞射結果圖 (c) GeS 的參照數數據圖............................40
圖 4. 3 (a) GeS 之選區繞射圖(b) GeS 之 HRTEM 影像 (c) GeS 之HRTEM 影像轉傅立葉轉換圖 .................................................43
圖 4.4 Raman 樣品試片 ...........................................45
圖 4.5 (a) GeS 塊材 c 平面的未極化拉曼 (b) GeS 塊材 c 平面的極化拉
曼 z(x,y) (c) GeS 塊材 c 平面的極化拉曼 z(x,x) ...................45
圖 4.6 硫化鍺穿透實驗的未極化及平行樣品 a 軸和垂直 a 軸結果圖........46
圖 4.7 非極化和極化熱調制.........................................49
圖 4.8 極化熱調制變溫圖 (a) 1.32-3 eV,變溫範圍 30-300 K............50
圖 4.9 能隙和溫度相依圖...........................................51
圖 4.10 於室溫下的極化激發螢光光譜圖...............................54
圖 4.11 (a) 於 10 K 下未極化的光激發螢光全譜圖 (b) 於 10 K 下,FX激發螢光光譜圖.........................................................54
圖 4.13 GeS 的 DAP 和雷射能量相依圖...............................55
圖 4.12 GeS 的 FX 與溫度相依圖....................................55
圖 4.14 GeS 的 DAP 與溫度相依圖 ..................................55
圖 4.15 極化熱調制和激發螢光在 300K 實驗結果.......................56
圖 4.16 極化熱調制和激發螢光在 30K 實驗結果........................56
圖 4.17 非極化和極化表面光電壓圖...................................58
圖 4.18 硫化鍺光電導圖............................................59
表索引
表 3.1 Raman 極化方向 ...........................................17
表 4 .1 經 EDS 分析後,硫化鍺晶體的成分組成比例.....................38
表 4.2 GeS 之晶格常數 a、b、c,第一筆為實驗結果,後兩筆為文獻資料......41
表 4. 3 (010)、(100) 、(110)、的晶面間距..........................43
表 4.4 非極化和極化熱調制.........................................49
表 4.5 Varshni 經驗式擬合獲得 Ei(0) 、αi、βi......................51

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