以化學氣相沉積法製成之單壁奈米碳管在柵狀電極薄膜電晶體上的電性探討

Abstract

利用化學氣相沉積法(CVD)來生長單壁奈米碳管(SWCNT)，與其他製備方法比較，可在較低的溫度之下製造出較高純度的奈米碳管，不但可以節省能量，並且此法可直接將奈米碳管生長在所需的基板上，不需額外的純化與轉置過程，降低了元件製作的複雜度。 在本論文中，我們將化學氣相沉積法所製成之單壁奈米碳管，沉積在矽基板上做為薄膜，製成薄膜電晶體(thin film transistor)，並對其做電性的探討。本實驗利用對於化學氣相沉積法生長環境的控制，在 n-type 的矽基板上生長出不同長度的奈米碳管(p-type)，並在其上製作不同間距(channel length)的平行電極或是柵狀電極(interdigitated electrodes)，最後製成薄膜電晶體進行電性的量測、比較與分析。 電晶體的電性會隨著碳管長度的不同而改變，呈現正相關但並非完全正比的關係；而柵狀電極雖然會提高電流，也會因為拉近了電極間距，而影響其開路/關路電流比。本論文結合了對碳管長度與電極形狀的探討，嘗試生產出更高效能的奈米碳管薄膜電晶體。

Compared to other methods of growing single-walled carbon nanotube (SWNT), chemical vapor deposition (CVD) can produce purer SWNT at lower temperature, which also has the particular advantage of energy conservation. Moreover, with the CVD method, we can directly eposit single-walled carbon nanotube (SWNT) thin films on a substrate without further purification and transfer. By doing so, we can make those procedures easier. We deposit CVD-SWNT networks with different tube lengths on n+ silicon substrate by adjusting the growing conditions. The SWNT networks are placed on substrates as a thin film of CNT thin film transistors (CNT-TFTs) with a range of channel lengths and different electrode shapes (parallel or interdigitated electrodes). Then, electrical measurement was performed. It is found that electrical properties of CNT-TFT can be optimized by increasing SWNT tube length, but they do not have a simple linear relationship. Likewise, the use of interdigitated electrodes can increase urrent and has an effect on the on/off ratio by shortening the channel length and extending the channel width. In this thesis, we have successfully fabricated a CNT-TFT with higher efficiency by adjusting CNT length and TFT electrode shape.