奈米觸媒顆粒成長之奈米碳管應用於場效電晶體之研究

A Study of Field-Effect-Transistor with Nanoparticle Catalyst-grown Carbon Nanotube

黃啟華(Chi-Hua Huang)

指導教授 ： 黃榮山

國立臺灣大學/工學院/應用力學研究所/碩士(2005年)

https://doi.org/10.6342/NTU.2005.01447

摘要

隨著電子產業的蓬勃發展，為因應產品性能之提升及成本下降等問題，線寬微縮化已成為半導體工業發展之主流。近年來有機半體的掘起，可撓式電子技術在擁有可彎曲、重量輕及便宜等優勢下，也亦顯重要；剛好，奈米碳管本身具備良好的強度及可撓的優點，且又擁有小線寬和半導體之特性，故非常適合取代有現有的可撓式電子技術—有機半導體。
本論文嘗試利用四氧化三鐵（Fe3O4）奈米顆粒成長奈米碳管。經適當選擇觸媒金屬顆粒尺寸及材料—四氧化三鐵，以做為成長奈米碳管之種子（觸媒金屬），再藉由化學氣相沉積（CVD）設備，本研究已成功地於四氧化三鐵上成長出奈米碳管。
為了能夠操控奈米碳管在基板上的成長方向，以便能靈活的應用奈米碳管，本論文提出了利用奈米碳管的成長機制，來控制奈米碳管的成長方向。為達成控制奈米碳管成長方向，本研究將利用簡單的電方式（異性相吸及不均勻電場, 5 V）來操控奈米觸媒金屬顆粒，以使奈米觸媒金屬顆粒吸附於電極之側壁；當成長奈米碳管時，奈米碳管本身的成長機制，便會使奈米碳管沿著電極側壁的法線方向成長。在操控奈米觸媒金屬顆粒的同時，本研究利用全反射式螢光顯微鏡，觀測標定上螢光分子的奈米觸媒金屬顆粒，藉螢光分子在顯微鏡下的運動，可達成奈米等級的動態觀測。
由於在電的操控方式下，會使得電極燒蝕，故我們巧妙的設計幾何形狀，來取代電的操控方式。首先，我們利用{100}的矽晶圓和微機電濕式蝕刻（KOH）的方式，蝕刻出一斜面；再運用金屬剝離法（lift-off）的方式，使得奈米觸媒金屬顆粒置於斜面上，如此一來，便達成同樣的目的了。在成長奈米碳管時，為區隔氣流方向對成長奈米碳管的影響，我們將同時置兩個相同設計型式的晶片於成長設備中—其中一個晶片之溝槽平行於氣流方向，另一個則是垂直於氣流方向。由實驗結果發現，所成長的奈米碳管，的確有朝斜面法線方向成長的趨勢。因此，我們推斷利用成長機制的方式，去控制奈米碳管成長方向是具有影響力的。若是未來能夠經由更加嚴謹的實驗來加以証明，此控制方法將具有「定位址」及「指向性」兩大功能；而且此方法在定位址的同時，可同時控制奈米碳管成長的方向。
為了証明利用奈米碳管發展可撓式電子技術的可行性，本研究將利用所成長的奈米碳管製作奈米碳管電晶體。在量測完奈米碳管電晶體電訊號後，發現有p型和p型與n型共存之雙載子（ambipolar）兩種型式。所製作的p-type電晶體，訊號的開關比（ON/OFF ratio）高達104；而所製作出具有雙載子的電晶體，將可替代n-type電晶體，以製作出最基本的邏輯電路元件—互補式金屬氧化半導體元件（CMOS device），以達成利用奈米碳管電晶體製作邏輯電路的目標。未來，再結合微機電製程技術，便可把奈米碳管電子技術轉置於可撓式基板。

關鍵字

奈米碳管 ； 場效電晶體 ； 奈米碳管場效電晶體 ； 指向性 ； 奈米顆粒 ； 奈米觀測 ； 化學氣相沉積

並列摘要

Flexible electronics and continuous miniaturization of current semiconductor technology are a technology roadmap that research and industries are devoted to pursue in next generation. Flexible electronics involves manufacturing that does not require nearly 2 billion fabs, and is environmentally responsible. Some of these technologies involve semiconductors fabricated on plastic substrates. Others involve organic semiconductors made with materials not seen in today’s semiconductor industry. Carbon nanotubes that possess semiconductor characteristics and nano-scale size also combine strength and flexibility, so they are excellent candidates for flexible electronics. The latest result of the carbon nanotube on polyimide reported its mobility at the same order of magnitude, but slightly lower to that in polycrystalline silicon. The paper presents the field-effect transistor (FET) with nanoparticle catalyst-grown carbon nanotubes (CNT) as device p-channels or n-channels. The nanoparticle material of Fe3O4 is newly selected as an experimental catalyst due to its size down to be around 6 nm that allows the growth of single-wall carbon nanotube. The carbon nanotubes were grown across source-drain electrodes in FETs. The present CNT-based device possesses p-type or/and ambipolar characteristics. The on/off switching ratio of p-type CNT-FET achieves a magnitude of 104. Meanwhile, the CNT-FET exhibits ambipolar characteristics that have both n-channel and p-channel effects on the same device. In other words, it is feasible to manufacture CMOS device in one device rather than the integration of p-MOS and n-MOS devices.
In addition, by taking advantages of nanoparticles and its growth characterisctics, the attempt to apply electrical fields for particle manipulation and to manufacture directional growth of CNT was to address particle in specific sites with specific CNT growth direction. The total internal reflection fluorescent microscopy was used in observation of nanoparticles manipulated in liquid under external fields. The preliminary result demonstrates the feasible visualization of particle movement in near-wall region. However, the electric field applied generates bubbles in liquid at both electrodes, reducing the quality of visual images. In addition, use of the slanted surface has been proven to grow directional CNTs in this study. With the use of anisotropic etched surface as a CNT growing substrate of the nanoparticles, the SEM picture demonstrates its feasibility of directional growth of CNTs. Based on the results of the present study, the CNT addressing and growth direction are potential to make the realization of CNT-based FET in near future.

並列關鍵字

carbon nanotube ； field-effect-transistor ； carbon nanotube field-effect-transistor ； directionality ； nanoparticle ； nano-measurement ； chemical vapor deposition

參考文獻

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