單壁奈米碳管是由一層石墨層捲曲成中空圓柱狀，兩端分別由似C60的半球結構組合而成。隨著石墨層捲曲的方向（稱為螺旋性），單壁奈米碳管會因其結構與直徑而呈現金屬或半導性的電特性。為了未來元件的應用，單壁奈米碳管的臨場成長與直徑控制儼然已成為目前研究團隊爭相研究的目標。在此，我們成功地提出利用催化裂解化學氣相沉積法在Mo/Fe/Al/SiO2的催化系統中合成高品質、窄直徑分佈的單壁奈米碳管。隨著對SiO2、Al、Fe 厚度的改變，我們發現Al對單壁奈米碳管的品質與產量有很大的貢獻。同時，我們籍由一系列的製程設計與規劃，可以得到最佳化的催化系統參數Mo(0.5nm)/Fe(1nm)/Al(5nm)/ SiO2(100nm)，其幾乎無雜質、結晶性佳（拉曼光譜G/D比超過45）且直徑分佈在0.8-1.4nm（大多數落在1.2nm）的單壁奈米碳管也在文中呈獻。最後，我們提出機制解釋並歸納說明奈米碳管品質與直徑隨催化系統參數而改變的原因。並期望在本實驗室的研究努力下，將高比例、均一直徑的單壁奈米碳管應用在CNT-FET元件上。

　　A single-walled carbon nanotube (SWNT) is a graphene layer rolled up into a cylinder, with its end cap structure similar to the half of C60. Depending on their (m, n) indices, SWNTs have different electrical properties. SWNTs can be metallic, semiconducting or small-gap semiconducting, depending on their structure and diameters. So control of the diameter of single-walled carbon nanotubes becomes the challenge of developing SWNTs-based nanoelectronic devices. A reliable method of controlling the diameter distribution of single-walled carbon nanotubes is needed. In this thesis, we presented a study of synthesizing high quality SWNTs with narrow diameter distribution by optimizing the Mo/Fe/Al/SiO2 catalytic system in thermal CVD. It was found that thickness of Al layer had significant effects on the quality of SWNTs. A high quality, almost bundle-free, SWNTs with G/D area ratio of 45 was obtained by optimizing the catalytic system with Mo(0.5nm)/Fe(1nm)/Al(5nm)/SiO2(100nm) multi-layer catalyst and the CVD growth process parameters. A narrow diameter distribution of 0.8~1.4 nm (mostly ~1.2 nm) was achieved. Finally, we summarized these results by proposing a SWNTs growth mechanism with multi-layer catalytic system to explain the effects of varying the thickness of each layer.

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