臺灣博碩士論文加值系統

自從奈米碳管被發現後，其具有許多獨特的特性，包括了高楊氏係數、高導電性、高場發射效應等等，因此奈米碳管的應用相較於其他材料更受到學術界與產業界廣泛的注意。合成奈米碳管的方式有許多種，本研究是採用電子迴旋共振式電漿輔助化學氣相沉積法(ECR-CVD)來合成奈米碳管，並分析奈米碳管的表面形態與製程參數之關係。
本研究主要目的在於建立本實驗機台合成奈米碳管(CNT)在n-type Si wafer的最佳製程參數，並提高其再現性，以利後續的奈米碳管/n-型Si接面特性研究計畫。在本研究實驗過程中，用電子束蒸鍍(E-beam)的鎳薄膜做為成長奈米碳管的金屬觸媒，再用電子迴旋共振電漿輔助化學氣相沉積法(ECR- CVD)；於ECR-CVD製程中，使用CH4/N2做為反應氣體，在相對較低的溫度500℃下，使奈米碳管生長在1cm2 Si基板上，並改變其成長時間長短、微波功率、氣體流量等等的參數，使奈米碳管長度產生變化。在結構分析上，藉由掃描式電子顯微鏡(SEM)來觀察奈米碳管的表面型態，最後在以電性量測確認奈米碳管表面型態/長度對CNT/n-Si接面特性。
研究結果表示，ECR-CVD製程出的奈米碳管長度大約0.3µm~2.6µm，較佳的製程功率大約440W；鎳觸媒經過前處理製程所合成的CNT，其準直性較於無前處理製程好；在霍爾量測的結果顯示以ECR-CVD在CH4/N2的氣氛下所合成的CNT，其主要載子為電子。CNT/n-Si接面特性會隨著CNT密度變高而變好，較短的CNT與Si之接面其理想因子n ~ 1。隨著CNT長度的增加n > 1。

Since the discovery of carbon nanotubes(CNTs), CNTs have attracted intensive interest on nanotechnology due their unique properties, such as high Young modulus, high conductivity, and high field emission efficiency at low turn-on voltage. Many potential applications use their unique properties, ex. silicon hetero-junction solar cells. Methods for the synthesis of CNTs include arc-discharge, laser vaporization, thermal chemical vapor deposition (CVD), plasma enhance chemical vapor deposition (PECVD) and electron cyclotron resonance CVD (ECR-CVD). In consideration of the advantage of high dissociation percentage of the precursor gases and high uniformity of plasma energy distribution, the ECR-CVD is adopted for this study.
In this study, multi-walled carbon nanotubes (MWNTs) were synthesized on a silicon substrate at relatively low temperature 500℃, using an ECR-CVD. Mixing gases of Methane (CH4) and Nitrogen (N2) were used as the carbon source and the plasma treated Ni film as the catalyst. Process parameters such as process time, microwave power, and gas flow were altered to optimize the properties of MWNTs on Si. The surface morphologies and microstructures of carbon nanotubes are examined by scanning electron microscopy (SEM).
The results show that ECR-CVD grown CNTs reveal vertically aligned character and the length of CNTs is varied from 0.3μm to 2.6μm.The density and uniformity of CNTs can be optimized using the plasma treated Ni catalyst under power of 440W. The signs of the Hall coefficients are negative, indicating that majority carriers are electrons in these films. CNTs/n-Si junction property depends on the density and length of CNTs. The ideality factor (n) of the best CNTs/n-Si junction is equal to one.

中文摘要 Ⅰ
英文摘要 Ⅱ
致謝 Ⅲ
目錄 Ⅳ
表目錄 Ⅴ
圖目錄 Ⅵ
第一章 緒論
1.1 前言 1
1.2 研究目的 2
第二章 基礎理論與文獻回顧
2.1 奈米碳管之基本理論 3
2.1.1奈米碳管之簡介 3
2.1.2奈米碳管之結構 4
2.1.3奈米碳管之基本電性結構 8
2.2 奈米碳管之合成方法 10
2.2.1電弧放電法(Arc discharge) 10
2.2.2雷射氣化法(Laser ablation method) 11
2.2.3化學氣相沉積法(Chemical vapor deposition method) 12
2.2.4CVD合成奈米碳管之機制 15
2.3 奈米碳管之吸附特性 18
2.4 奈米碳管之官能基化 19
2.4.1共價鍵作用官能基化奈米碳管表面 19
2.5奈米碳管之導熱特性 20
第三章 實驗步驟與實驗設備
3.1 實驗流程 21
3.1.1ECR-CVD成長奈米碳管實驗流程 21
3.2 實驗設備 22
3.2.1電子束蒸鍍系統 (E-beam) 22
3.2.2奈米碳管製程設備 24
3.2.2.1電子迴旋共振化學氣相沉積系統(ECR-CVD) 24
3.2.2.2電漿系統 24
3.2.2.3真空系統 25
3.2.2.4壓力控制系統 25
3.2.2.5氣體流量控制系統 27
3.2.2.6冷卻水系統 27
3.2.2.7基板加熱與偏壓系統 28

3.3 實驗步驟 29
3.3.1矽基板清潔 29
3.3.2備製奈米金屬觸媒粒子 30
3.3.3使用ECR-CVD生長奈米碳管 31
3.4 實驗材料 32
3.4.1基板材料 32
3.4.2E-beam蒸鍍靶材 32
3.4.3實驗反應氣體 32
3.5 實驗分析 33
3.5.1性質測試與分析 33
3.6 量測分析設備 34
3.6.1場發射掃描式電子顯微鏡 34
3.6.2場發射穿透式電子顯微鏡 35
3.6.3霍爾量測分析儀 36
3.6.4電流電壓量測 37
第四章 結果與討論
4.1 ECR-CVD奈米碳管之製作 38
4.1.1金屬觸媒之前處理 39
4.1.2前處理時間對觸媒表面形態之影響 40
4.1.3鎳觸媒顆粒大小對奈米碳管合成之影響 42
4.1.4微波功率對奈米碳管成長之影響 44
4.1.5製程時間對奈米碳管成長之影響 48
4.1.6氣體流量對奈米碳管成長之影響 50
4.2 ECR-CVD奈米碳管之霍爾量測 52
4.2.1不同基板之霍爾量測影響 53
4.2.2不同奈米碳管長度之霍爾量測影響 54
4.3 奈米碳管/N型矽晶異質接面之I-V特性分析 56
4.3.1暗電流I-V特性分析 56
4.3.1.1不同奈米碳管長度之暗電流分析 59
4.3.1.2PEDOT之暗電流分析 61
4.3.2光電流I-V特性分析 63
4.3.2.1不同方向成長奈米碳管之太陽能轉換效率 65
4.3.2.2不同奈米碳管長度之太陽能轉換效率 67
4.3.2.3PEDOT之太陽能轉換效率 69
第五章 結論 71
參考文獻 72

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