微波電漿輔助化學氣相沉積法合成碳奈米管之研究

Synthesis of Carbon Nanotubes by Microwave Plasma Chemical Vapor Deposition

張秋萍(Chiou-Ping Chang)

指導教授 ： 魏大欽

中原大學/工學院/化學工程研究所/碩士(2003年)

https://doi.org/10.6840/cycu200300449

摘要

碳奈米管是由類似石墨之六邊型網格所組成的中空柱狀體，直徑在1至50奈米之間，長度可達數微米。由於碳奈米管的結構對於本身的性質有重大的影響，故碳奈米管的合成方法及條件，不論是在碳源及觸媒的選用上，或是溫度和氣氛的調控，都非常的重要。本研究以微波電漿化學氣相沉積法合成碳奈米管，探討操作參數對碳奈米管結構之影響，並以電漿放射光譜來作電漿診斷，得知在不同實驗條件下，電漿內部組成及激發溫度之變化。
　　研究發現，利用微波電漿輔助化學氣相沉積法，以甲烷、氮氣與氫氣為進料，可在600℃下以鈷觸媒合成大量碳奈米管，管徑細小，約略分布於20奈米左右，進一步以穿透式電子顯微鏡分析推論，本研究所成長之碳管成長機制應為頂部成長機制，且進料氣體雖添加氮氣，卻無竹節狀之結構。於沈積碳奈米管時之電漿放射光譜可偵測出CN及H 自由基，其中CN應為合成碳奈米管的主要碳源，而H 自由基則可蝕刻觸媒上所沈積之非晶質碳膜，保持觸媒活性。再者，由診斷分析後得知電漿物種之激發溫度介於3,500～5,000 K。

關鍵字

微波電漿輔助化學氣相沈積 ； 碳奈米管 ； 電漿放射光譜

並列摘要

Carbon nanotubes have attracted much attention since the work by Iijima in 1991. Arc discharge was first employed for synthesizing carbon nanotubes. However, the high processing temperature in arc discharge prohibits the utilization of substrate, as well as the control of diameter, length, alignment, and purity of the nanotubes. In this study canbon nanotubes were synthesized via microwave plasma-enhanced chemical vapor deposition. The plasma can generate abundant reactive radicals by electron impact, allowing the carbon nanotubes to grow on a variety of substrates at low temperatures. The plasma can also be used in the etching of catalyst particles, thus reducing the size of the catalyst, and hence the diameter of the growing nanotubes.
It was found in this study that carbon nanotubes could be synthesized on the cobalt catalyst in CH4/N2/H2 plasmas at 600oC. The diameters of nanotubes are about 20 nm. From TEM analysis, we suggest the mechanism of nanotubes is tip growing mode, and no bamboo structure exists in spite of nitrogen addition. Optical emission spectroscopy showed high concentration of CN, NH, and H radical species in the plasma. It is speculated that CN radicals are the main deposition precursor and H radicals can etch amorphous carbon deposited on the surface of catalyst to maintain catalyst activity in carbon nanotubes synthesis. The excitation temperature is between 3,500~5,000 K.

並列關鍵字

OES ； Microwave PECVD ； Carbon nanotubes

參考文獻

Badzian, A., T. Badzian, E. Breval, A. Piotrowski, “Nanostructured, Nitrogen-Doped Carbon Materials for Hydrogen Storage.”, Thin Solid Films 398-399, 170 (2001).

Berber, S., Y. K. Kwon, and D. Tománek, “Unusually High Thermal Conductivity of Carbon Nanotubes.”, Phys. Rev. Lett. 84, 4613 (2000).

Bethune, D. S., C. H. Kiang, M. S. DeVries, G. Gorman, R. Savoy and R. Beyers, “Cobalt-Catalysed Growth of Carbon Nanotubes With Single-Atomic-Layer Walls.”, Nature 363, 605 (1993).

Bower, C., and W. Zhu, S. Jin, and O. Zhou, “Plasma-Induced Alignment of Carbon Nanotubes.”, Appl. Phys. Lett. 77, 830 (2000).

Chatei, H., J. Bougdira, M. Remy, P. Alnot, C. Bruch, J. K. Kruger, “Effect of Nitrogen Concentration on Plasma Reactivity and Diamond Growth In a H2-CH4-N2 Microwave Discharge”, Diam. Relat. Mat. 6, 107 (1997).