- 學位論文
利用化學氣相沈積法成長單壁奈米碳管於電子元件上之應用
Chemical Vapor Deposition Growth of Single-Walled Carbon Nanotubes for Electronic Applications
摘要
奈米碳管因為其特殊的機械與電子特性，使它成為一個受到矚目的材料。奈米碳管屬於一維度的材料，更使得它在電子元件上的應用，如作為場發射電子源，原子力顯微鏡探針等，有相當大的潛力。對於奈米碳管於場效電晶體上的應用，比起其他更能凸顯其特殊電子特性。然而為了符合工業上大量製造元件的需求，傳統以電弧放電法成長奈米碳管的方式，較為不適用。為追求此工業目標，利用化學氣相沈積方法成長奈米碳管為最好之解決方法。本論文即探討利用高溫化學氣相沈積方法，並搭配特殊雙層結構催化劑組成，完成在矽基板上選區大量成長高品質的單壁奈米碳管，並進而改變參數以達到單壁奈米碳管直徑分佈控制的目標。 接著，利用半導體性的單壁奈米碳管作為場效電晶體中的傳導通道部分，完成以奈米碳管為主的場效電晶體元件製作。並探討元件結構與其雙極性傳輸特性與否的關係。除此之外，利用不同種類金屬作為元件中的源、汲極接觸金屬，也有助於我們探討奈米碳管為主的場效電晶體本身傳輸機制。 所有研究，希望能使本製程有助於提高單壁奈米碳管在工業上應用的可行性。
並列摘要
Carbon nanotube (CNT) has been considered as an alternative material and receiving much attention because of its excellent mechanical and unique electronic properties. The prototype one-dimensional (1D) material has its potential in nanoelectronics, field emission devices, scanning probes, high strength composites and many applications. For the applications of nanoelectronics like carbon nanotube field effect transistors (CNFETs) and field emission devices, the selective growth of high quality CNTs and pursue an economies of large-scale production of nanoelectronics depend on precise and controllable processes. This very problem can be solved in this work by using catalytic chemical vapor deposition (CCVD). A patterned double-layered catalytic configuration comprising of nickel thin film and oxide upper layer accompany high temperature chemical vapor deposition (CVD) can lead high quality single-walled carbon nanotubes (SWNTs) grow across two catalytic patterns laterally. This selective growth of high quality SWNTs on substrate will simplify the process of nanoelectronic devices and eventually lead to commercialization. However, the electrical property of SWNTs deeply depends on their structure and is not easily to control. For some applications, it might be sufficient to sort semiconducting SWNTs. For approaching the practical application like CNFETs, however, it has been suggested that small diameter SWNTs are supposed to be an advantage to behave as semiconducting and narrow diameter distribution is needed to reduce the device variability. I present a method of modulation of double-layered catalytic configurations to control the diameters of SWNTs as small than 1.0 nm. This should demonstrate an enormous potential for an economies of large-scale production of CNFETs. Further, I show various CNFETs devices made of CVD grown SWNTs. An undesirable ambipolar behavior and accompanying low ON/OFF ratio at high source/drain voltage of conventional CNFETs with thin oxide layer were observed in the most devices. Thus, SWNTs based devices with asymmetric gating structures comprising of a different oxide thickness for the gate oxide at the source and drain contacts. The combination processes and the resulting electrical characteristics of CNFETs with the asymmetric structures can not only converse the undesirable ambipolar behavior of CNFETs to unipolar but solve the restriction of source/drain voltage. Another application based on CNTs is field emission devices. The common field emission devices with vertically aligned CNTs have been reported. Here, lateral SWNTs field emitters conducted on the silicon substrate can be obtained by using the same catalytic configuration and consequent CCVD. The promised field emission electrons from the bodies of SWNTs can behave a high uniform luminance. It could also be a feasible method to fabricate field emission devices. To fabricate and characterize CNFETs with heterometallic contacts simply, dispersion as-grown SWNTs on the oxide substrates were adopted. Consequent definition of heterometallic contacts, the devices behave as unipolar CNFETs as asymmetric structure CNFETs and also pure Schottky diodes. These developed processes of fabrication of CNTs based electronics are expected to be applicable and feasible for CNTs coming to the industrial products.