奈米碳管場發體在可撓性碳布上之成長及特性研究

Abstract

奈米碳管場發射顯示器是一種跟陰極射線管顯示器比較薄的平面顯示器。有較低的功率消耗，及預計成為下一個世代新且大的平面顯示器。成長在碳布上的奈米碳管有較低的操作電場是由於碳布的編織幾何分布。所以奈米碳管成長在可撓性碳布上在微電子工業有實際且方便的應用。在此篇論文中，我們比較利用化學氣相沈積法成長在碳布上的催化劑奈米顆粒及奈米碳管，在不同的前處理及成長條件下，如前處理時間、溫度、氣體流量以及成長時的時間、溫度、氣體流量時的直徑尺寸大小及場發射特性。在我們的實驗裡，成長過程使用乙烯當成製程氣體，氫氣及氮氣為稀釋或承載氣體，鎳為催化劑，鈦及鋁當緩衝層。實驗結果顯示，催化劑奈米顆粒的尺寸大小跟奈米碳管的直徑大小相同而且大小尺寸差異滿明顯的，最大的碳管尺寸為160 nm，最小為12nm。根據此實驗結果，可以藉由控制催化劑奈米顆粒的尺寸大小來形成想要的直徑尺寸的奈米碳管。另外，我們也發現當我們加入鋁當緩衝層時，形成在碳布上的催化劑奈米顆粒及奈米碳管尺寸比沒有加入緩衝層及加入鈦金屬為大。因此，可以藉由加入不同的緩衝層來控制奈米碳管的直徑尺寸。根據場發射的結果顯示，場發特性跟不同的前處理及成長的參數有關。此篇論文中最佳的起始電壓在時間30分鐘、溫度550℃、氫氣流量100 sccm氮氣流量500 sccm時為8.2 V/μm，此值遠低於Jo, S. H et發表約0.34 V/μm。此差異可能是因為催化劑成長的不同，此論文是用熱蒸鍍的方式，Jo, S. H et是用濺鍍的方式。

Carbon nanotube based field emission displays (CNT-FEDs) are generally described as devices for thin flat panel display compared with Cathode Ray Tube (CRT), having low power consumption and be expected to become new and large flat panel display in next generation. The lower operating electric field of carbon nanotubes grown on carbon cloth is due to geometrical configuration of woven nature of carbon cloth. So the carbon nanotubes grown on flexible carbon cloth has practical and convenient applications of microelectronics. In this thesis, we compare size and field emission characteristics of catalyst nano particle with carbon nanotube grown on carbon cloth under the various conditions, pretreated time, temperature, gas flux, and growth time, temperature and gas flux by thermal chemical vapor deposition. The growth process uses ethylene (C2H4) as the process gas, hydrogen (H2) and nitrogen (N2) as the carried/ diluted gas, nickel as catalyst and titanium (Ti), aluminum (Al) as buffer layers in our experiment. The experiment results reveal that the diameters of catalyst nano particle are the same as of carbon nanotube and the size difference of CNTs growth on carbon cloth is evident. The biggest size of CNT is about 160 nm, and the smallest size of CNT is 12 nm. According to the results, we can grow the diameter size of carbon nanotube that we want by controlled the size of catalyst nano particle. In addition, we also find that the catalyst nano particle and carbon nanotube formed on the carbon cloth with deposited nickel are larger than the titanium as buffer layer, but it is smaller than the aluminum as buffer layer. So we can control the diameter size of carbon nanotube by adding different buffer layer. According to the field emission results, it reveals that the emission characteristics are relation to various pretreated and growth parameters. The best turn on field of carbon nanortubes growth on carbon cloth in this thesis is near 8.2 V/μm in conditions, temperature: 550℃, H2 flux: 100 sccm, N2 flux: 500 sccm, time: 30 min, and is lower than results that Jo, S. H et. al. published in 2004. Maybe the difference is due to methods for catalyst deposited and type of catalyst. In this thesis, we deposited catalyst by using thermal evaporator, and it is by sputter deposition in that published.