Chemical Vapor Deposition Growth of Single-Walled Carbon Nanotubes for Electronic Applications

• Main Authors: Lee,WeiYang, 李威養
• Other Authors: Tsai,ChuenHorng
• Format: Others
• Language: en_US
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/64021946056667453043

博士 === 國立清華大學 === 工程與系統科學系 === 96 === 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.