微波電漿中氮氫比例對奈米碳管成長的影響

Effect of hydrogen and nitrogen percentage in microwave plasma on carbon nano tube growth

黃聖涵(Sheng-Han Huang)

指導教授 ： 張慎周

崑山科技大學/工程學院/電機工程研究所/碩士(2006年)

摘要

本研究採用微波電漿化學氣相沉積系統(MPCVD)在低溫(2500C)下合成奈米碳管。利用微波氮氫混合電漿及純氮、純氫電漿對鎳催化劑薄膜進行預處理，藉由觀察不同氮氫氣體比例電漿源預處理鎳催化劑薄膜的表面型態、後續成長的奈米碳管及場發射特性之影響，進而探討合適的氣體電漿源，改變預處理製程壓力、微波功率達到控制預處理參數對成長奈米碳管之影響。最後探討在成長奈米碳管製程氣體中，加入氮氣對奈米碳管成長及場發射特性之影響。
由實驗結果得知，固定預處理製程壓力25Torr與微波功率450W中，氮電漿轟擊蝕刻鎳薄膜效果比氫電漿大。在不同氮氫比例中，以氮氫比例(1:3)電漿源預處理鎳薄膜結果有較小的鎳顆粒粒徑及較高的顆粒密度，後續成長奈米碳管的品質也較佳(有低的開啟電場及高的電流密度)。預處理製程壓力在25Torr時，鎳薄膜經由處理後所形成的顆粒大小最平均，製程壓力低於(20Torr)或高於(30Torr)時，鎳薄膜處理後會形成不均勻的顆粒大小。隨著增加預處理的微波必v可使鎳顆粒平均粒徑變小、平均間距變大。當微波功率過高時(850W以上)，鎳顆粒會產生聚結(Coalescence)效果，使得鎳顆粒平均粒徑變大、平均間距變小、顆粒大小變不均勻，對後續成長奈米碳管也會有直接的影響。
最後探討在成長奈米碳管製程溫度6000C中，改變不同氮氣流量通入製程氣體(氫氣及甲烷)中，發現可以使成長之奈米碳管的管徑變細、管長變長且碳管密度變高。

關鍵字

奈米碳管

並列摘要

Microwave plasma chemical vapor deposition (MPCVD) was used to produce carbon nano tube(CNT) at 2500C in this work. Different percentage of N2/H2 microwave plasma was pretreated on nickel films into CNT producing catalyst. Surface morphology of nickel films after pretreatment, following grown CNT and its field emission properties were studied. After that, effects of chamber pressure, microwave power during pretreatment and N2/H2 percentage during growing CNT were also studied.
Experimental results show N2 plasma would have powerful sputter etching effect to nickel films than H2 one. Small grains and high grain density which benefit growing CNT are produced from N2:H2=1:3. Better CNT quality was experimentally observed.
Chamber pressure result shows pretreated ni grain size are irregular in either too high too low pressure. Optimum pressure in our MPCVD system is 25 torr. Microwave power result indicates increasing power, the sizes of the pretreated nickel particle becomes small and distance between particles large. As the power still increased over 850 W, sintering effect among nickel particles seems to appear: the grain size becomes irregular. Suitable N2 percentage in growing CNT can control the CNT diameter and density.

並列關鍵字

carbon nanotube

參考文獻

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