以熱裂解方式成長低密度奈米碳管與場發射特性量測

Study of the growth of low-density carbon nanotubes by thermal CVD and the measurements of their field emission characteristics

李彥緯(Yen-Wei Li)

指導教授 ： 賴再興

中原大學/理學院/應用物理研究所/碩士(2005年)

https://doi.org/10.6840/cycu200500170

摘要

中文摘要

本論文主要是探討奈米碳管的密度控制與其場發射特性的量測，希望能將最佳碳管密度所擁有的好場發射結果應用在場發射顯示器（Field emission display,FED）與其他電子元件上。本論文首先從奈米碳管的成長機制開始，進而由不同的製程方式中整合出好的碳管密度控制製程，再找出各種密度下成長出準直碳管的最佳參數，最後，對各種密度的奈米碳管進行場發射特性的量測分析，與應用價值的討論。我們先有兩個假設：（一）奈米碳管準直的成長是不需受惠於彼此間的凡德瓦爾力的影響；（二）奈米碳管的場發射特性是會受到彼此間屏蔽效應的影響。本論文中，我們經由實驗驗證了這些假設的正確性。

我們的實驗包含三大主題：（一）前處理與氬離子蝕刻對催化劑的影響：藉著改變氬離子蝕刻時間與催化劑的薄膜厚度來觀察。（二）氣體對準直碳管的影響：藉著改變成長氣體比例與成長溫度來觀察。（三）場發射特性量測：藉著改變碳管的密度來觀察。經由以上的實驗結果與分析，驗證了我們對奈米碳管彼此間效應的假設，進而了解到奈米碳管的密度、結構與場發射特性之間的關係：密度過高與石墨化程度較差（結構較差）的奈米碳管，其場發射啟始電場較高，也導致場增強因子（β）的值較小。

總之，我們在熱裂解化學汽相沉積法中實現了低密度奈米碳管的成長，且由場發射特性量測的結果中，分析歸納出與奈米碳管場發射特性相關的各種因素，這對日後奈米碳管在場發射顯示器上的應用會有不錯的幫助。

關鍵字

低密度 ； 場發射 ； 奈米碳管 ； 離子蝕刻 ； 熱裂解化學汽相沈積法

並列摘要

Abstract

This thesis is mainly focused on the density control and the measurements of the field emission characteristics of the carbon nanotubes(CNTs), and in the hope of applying the good field emission, properties possessed by the best density of carbon nanotubes, to the field emission display(FED) and other electronic devices. This study was first started with the growth mechanism of the CNTs, then proceed to develop a growth process for better density control of the CNTs. After that, to find out the optimal growth parameters of the aligned CNTs under various density. And finally, the measurements, analyses, and discussions of the field emission property of the CNTs under various density. Basically, we set two premises : (1) The growth of the vertical CNTs needn’t be beneficial to the effect of the van der Waals forces. (2) The field emission characteristics of the CNTs is influenced by the screening effect of one another. In the thesis, the validity of these premises was verified by our experiments.

Our experiments contained three main subjects：(1) The influences of the pretreatments and Ar-ion milling on the catalytic metal：we observed them by the change of the ion milling times and the thickness of the catalytic films. (2) The effects of the growth gas on the vertical carbon nanotubes : we observed them by the changes of the ratio of flow rate of the growth gases and the growth temperatures. (3) the measurements of the field emission characteristics of the CNTs：we observed them by the change of the density of the grown carbon nanotubes. We verified our premises concerning the interactions between the carbon nanotubes via these experiments and the analyses of our results, and found the relationship between the density, the structure, and the field emission characteristics of our carbon nanotubes：carbon nanotubes with exceeding densities and worse graphite structures also lead to smaller field-enhancement factors and higher turn-on electric fields.

In summary, using thermal CVD, we have grown low-density CNTs by the ion-milling technique. From the measurements and analyses of the field emission characteristics of our grown CNTs, we induced several factors which will be of great helpful for the applications of CNTs to the FED in the future.

並列關鍵字

carbon nanotube ； field emission ； thermal CVD ； low density ； ion milling

參考文獻

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