以熱裂解法成長奈米碳管機制的研究

Study of the growth mechanism of CNTs by thermal CVD

來俊帆(Jiun-Fan Lai)

指導教授 ： 賴再興

中原大學/理學院/應用物理研究所/碩士(2004年)

https://doi.org/10.6840/cycu200400519

摘要

中文摘要
本論文主要是探討準直奈米碳管的成長機制，希望在最短的時間內能將準直的奈米碳管應用在相關的電子元件上。本論文將從探討碳管的成長機制開始，進而找出成長準直碳管的最佳製程參數，並且為了日後碳管的各種不同應用，我們最後將研究如何使碳管有不同的形貌、結構以及成長位置。對於碳管的成長機制，我們提出了一個構想，我們認為奈米碳管的成長至少包含三個步驟，其前提是假設在碳管的成長過程中金屬顆粒是處於類液態。這三個步驟分別是:(一)碳原子(在適當溫度下碳源氣體在催化劑顆粒表面脫氫所產生)開始擴散入催化金屬; (二)碳原子在催化金屬中經由擴散逐漸累積達到碳管成核濃度並使催化劑金屬變為(膠囊形或球形) ; (三)碳管成核並經由持續的擴散使其自飽和的催化劑金屬表面析出。在論文中我們會經由實際的實驗來驗證這個構想的正確性。
本論文中，我們針對氨氣對奈米碳管成長的影響做了ㄧ系列的探討，嘗試去釐清氨氣在碳管成長時所扮演的角色，另一方面，就目前碳管在場發射顯示器的應用而言，我們首先必須找出成長準直碳管的方法，接著是如何降低碳管的密度，最後是在低溫環境成長奈米碳管，因此我們經由下列幾點開始討論氨氣對碳管成長的影響(1)氨氣前處理對催化劑的影響，(2)氨氣對碳管成長過程的影響，在前處理的實驗中改變(1)溫度，(2)氣體比例，(3)催化劑膜厚的改變，來觀察不同的結果進而釐清氨氣在這階段所做的工作;在碳管的成長過程中，我們經由(1)成長氣體比例，(2)溫度的改變，來分析及驗證本論文中所提的奈米碳管成長機制的構想。
在本論文中，我們提出了一個碳管成長機制的構想，並且我們也直接從實驗結果來驗證這個構想的正確性。最主要的研究成果是，我們如預期地成長出準直的奈米碳管，並且我們也解決了一些碳管應用在場發射顯示器上的問題，例如 (1) 我們能在薄膜催化劑上簡單地改變碳管的密度;(2) 我們可以在低溫(600以下)成長奈米碳管，因此我們確信經由不斷的研究，碳管在各種應用的構想，已經不再是遙不可及。

關鍵字

奈米碳管 ； 熱裂解法成長奈米碳管 ； 奈米碳管機制

並列摘要

Abstract
This thesis mainly devoted to study the growth mechanism of the vertical CNTs(carbon nanotubes) by thermal CVD for their applications in various electronic devices. We started the study from the growth mechanism , then found out the optimal growth parameters of the vertical CNTs , and at last , we learned to vary the contour , structure and position of the growth CNTs for the sake of their application.
As for the growth mechanism of CNTs , we proposed a three-step growth model of the CNTs under the premises that the catalytic metal particles are liguid-like during the growth process. The three steps are (1) at proper temperature , the vapor of carbon source took hydrogen off on the surface of the metal particle , thereupon , the carbon atom start to diffuse into metal particle ;(2) the diffusion of carbon atoms goes on to reach the nucleation concentration , thereby , change the metal particle to become a sphere or capsule ;(3) the saturated carbon atoms nucleate on the surface of the catalytic metal then separated out as CNTs. The three-step growth model has been verified via our various experiments.
We have studied the effect of NH3 on the growth of CNTs in this thesis , and try to find out the role that NH3 played. On the other hand , for the application of CNTs in FED(field emission display) , one have to grow vertical CNTs on pattered metal , to cut down the density of the grown CNTs , and to grow the CNTs at lower temperatures. In this regard , we studied the effect of NH3 on the growth of CNTs via (1) the effect of thepretreatment of NH3 on the catalytic metal ;(2) the effect of NH3 on CNTs during their growing process. For the studies of the first part , we chose (a) pretreatment temperature (b) NH3 / Ar flow rate (c) the thickness of the catalytic field as our variational parameters ; for the studies of the second part , we choose (a) the flow rate of NH3 / Ar / C2H4 (b) growing themperatures as our variational parameters.
In summary , we have proposed a three-step growth model of the CNTs and verified by our experimental results. We have grown vertical CNTs on SiO2 substrate. Besides , we have solve some problems of the application of CNTs in FED , such as (a) the density of CNTs could easily be controlled on thin catalytic films ; (b) CNTs could be grown at lower temperature (~600℃). We believe that through continuous hard working , the application of CNTs in various fields is not far beyond reach.

並列關鍵字

CNTs ； CNT ； growth mechanism of CNTs

參考文獻

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