遠端監控智慧型微波電漿化學氣相沈積系統成長具有特定結構與性能之奈米碳管之研究

The Study of Growing CNTs with Specific Structure and Performance using the Remote-Controlled Intelligent MPCVD System

莊俊彥(Jyun-Yan Jhuang)

指導教授 ： 林啟瑞 ； 蘇春熺

國立臺北科技大學/機電學院/機電整合研究所/碩士(2007年)

摘要

本研究不同於傳統材料學門之研究方法，主要致力於建立微波電漿化學氣相沈積(Microwave Plasma Chemical Vapor Deposition, MPCVD)系統之遠端智慧型控制模組。目的為經由MPCVD系統中之微波電磁場調整器(E-H tuner)之智慧型參數調控，使成長後之奈米碳管因具有特定結構而獲得特定性能，因此提升實驗室等級之設備之工業化技術應用。
本研究主要運用模糊邏輯控制(Fuzzy Logic Control)之運算法則，其中利用以實驗獲得之微波電磁場調整器參數與奈米碳管微結構間之關係所建立之規則庫，將希望成長之碳管微結構作為單點模糊集合(Fuzzy Singleton)，以推論引擎將輸入之理想值模糊化，導入歸屬度函數(Membership function)中；再透過輸入理想值對應之規則庫中，依E-H tuner之參數，計算出此結構比值於資料庫中對應之E-H tuner的位置參數，並輸出至控制器作微波電磁場調整器之定位控制；同時透過反射功率計之監控使其選擇最佳之位置參數以成長奈米碳管。最終目的在於此控制系統能夠改善原有人工操作之缺點，大幅提高奈米碳管製程之效率與微結構重現性。另外並可結合網路連結於遠端電腦作奈米碳管成長時，電漿均勻度之觀察。
於多次實驗後之結果證明，微波電漿化學氣相沈積法用於奈米碳管製程時，會因微波源之電磁共振改變(亦即E-H tuner位置之不同)而造成奈米碳管微結構之不同；相反之，於相同位置處，經由拉曼光譜微結構檢測證明，本系統具有良好之再現性；MPCVD系統於微波反射功率為20 ％時，E-H tuner檔板於位置(X, Y)為(19.3 cm, 10 cm)之奈米碳管結構比與幾何外觀極佳，長徑比為1336.2，其拉曼光譜檢測之ID/IG值為0.336；另一方面當檔板位於(7.3 cm, 13.9 cm)處，反射功率同為20 ％，但膜厚及結構比皆屬於最差，其ID/IG值為1.32，長徑比為155.76。 根據場發射結果作比較，越低之結構比能夠擁有最低之場發射起始電場，其值約為0.54 V/μm，相對之下，結構比較差，其值為1.32之奈米碳管起始電場較高，其值為0.82 V/μm，因此經過本研究可發現奈米碳管場發射效應會因微結構不同而改變，但皆因本身之特性而有良好之場發射效應。
另一方面，微結構以拉曼光譜檢測之ID/IG值與其潤濕性結合，利用潤濕角量測系統，研究不同結構比值對應之潤濕角以及其電潤性，以推定CNTs微結構對該親疏水性之影響。實驗結果顯示，CNTs較一般材料具有極佳之疏水性；但隨著微結構之不同，其對應之潤濕角臨界水滴之滴定量也隨之不同，微結構中缺陷較多(ID/IG值為0.94)之CNTs試片，其於0.01 c.c.定量滴定下之潤濕角為139˚；而微結構比值優良(ID/IG值為0.336)之相同滴定下，潤濕角為150˚，且水滴更不容易附著於奈米碳管試片表面。於電潤性(Electrowetting)方面，微結構佳(ID/IG值為0.336)之奈米碳管，其電潤性具有非常明顯之變化，施加電壓4 V則親水性大幅提升，潤濕角變為36˚；相較結構比值較差(ID/IG值為0.844)，其電潤性較不明顯，施加電壓11 V時，潤濕角為95˚。因此藉由此研究，未來將能夠適用於控制微機電結構或流道之親疏水性，藉以達到流體與結構間流場或黏滯性之控制。

關鍵字

微波化學氣相沈積系統 ； 遠端智慧型控制模組 ； 微波電磁場調整器 ； 工業化技術 ； 模糊邏輯控制 ； 微結構重現性 ； 場發射特性 ； 電潤性

並列摘要

In order to improve the reproducibility of CNTs process, this study integrates the industrial technology and remote intelligent control method into microwave plasma chemical vapor deposition (MPCVD) system. An automatic fuzzy control scheme is used to adjust electromagnetic field distribution, plasma density, and reflected microwave power by E-H tuner position in the MPCVD system. Reflected microwave power as the main feedback signal. The intelligent control includes establishment of database, fuzzification of principal component, membership function, fuzzy inference rules, and defuzzification. The specific micro-structure ratio is a fuzzy singleton to input in fuzzy logic algorithm. This value figured out the corresponding E-H tuner position by database which included the relationship between E-H tuner position and micro-structure. The figured out position output to drive the linear cylinder achieved the corresponding position and started to grow CNTs.
The experimental results shown, an (X, Y) position of (19.3 cm, 10 cm) for E-H tuner adjustment is found to have the best average micro-structure ratio 0.336 (ID/IG ratio), the averaged films thickness is 41.77 μm, the averaged tube diameter is 31.26 nm. On the other hands, an (X, Y) position of (7.3 cm, 13.9 cm), the ID/IG is 1.32 and average films thickness is 9 μm, the averaged tube diameter is 57.78 nm. According to this result, not only micro- structure but also thickness and tube diameter were changed by different E-H tuner position, and each position had its corresponded micro-structure and reproducibility. Compared with these tow micro-structure by field emission test, the result shown that the lower ID/IG ratio the better turn on voltage 0.54 V/μm, but the turn on voltage of higher ID/IG ratio is 0.82 V/μm. Although the turn on voltage changed by different ID/IG ratio, but both CNTs samples had well field emission properties.
The results of contact angle measurement shown, CNTs had the bad wettability because of 145˚ average contact angle. All of the contact angles were not changed by different ID/IG ratio. On the other hands, the electrowetting property changed clearly by the external power source. As the results shown, the lower ID/IG ratio (0.336) the better electrowetting property when voltage during 0~4 V. But the higher ID/IG ratio (1.32) needed a higher voltage about 11 V to change its electrowetting property. Combined with these results of characteristics and MPCVD intelligent control system, this study improved the industrial value of MPCVD system. Therefore, this system could made more applications by high reproducibility CNTs process.

並列關鍵字

MPCVD system ； remote intelligent control ； fuzzy logic control ； micro-structure ratio ； E-H tuner ； industrial technology ； field emission property ； electrowetting property

參考文獻

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