Laser patterning technique of carbon nanotube thin films for optoelectronic and electronic devices

• Main Authors: Shiang-Kuo Chang-Jian, 張簡相國
• Other Authors: Jeng-Rong Ho
• Format: Others
• Language: en_US
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/51025388680515750980

博士 === 國立中正大學 === 機械工程所 === 98 === This thesis aims to develop new laser-based methods for processing carbon nanotube (CNT) thin film for potential applications to novel sensors and electronic and optoelectronic devices. With incorporating an accurate X-Y motion table, the Nd:YAG laser operating at 1064 nm is employed to print, pattern, thinning, and separate CNT thin films. Patterned CNT thin films, for application to cathode field emitters, touch panel screen, free-standing CNT backypapers, as well as CNT transistors, are presented in this thesis. First, a new laser transfer printing scheme is proposed to pattern multi-walled CNTs, MWNTs, for field emission cathodes on various substrates. Well-defined patterns with a feature size down to 10 ?m can be obtained and the I-V characterization demonstrates these CNT emitters possess a very low emission threshold, 1 mA/cm2 at 3.3 V/?m. The fast deposition rate and high degree of feasibility of using the substrate, as well as the fabrication environment, render the proposed approach a potential method for low cost fabrication of precision patterns for MWNTs. Subsequently, the laser is employed to separate MWNTs from a transparent substrate to fabricate a free-standing MWNT film, buckypaper. By introducing a patterned mask, buckypaper having surface patterns is straightforwardly fabricated, and, through a shaped support, a buckypaper possessing 3D curved surfaces can be directly formed. Besides, it is also demonstrated that, thin buckypaper, with thickness around 15 ?m, can be constantly fabricated that reveals the superiority over the available mass-produced methods for which buckypapers with thickness smaller than 50 ?m still present challenges. Finally, the laser is used to transfer printing of networked single-walled CNTs (SWNTs) for carbon nanotubes field-effect transistor, CNTFETs. Here, the transient current of the n-type CNTFET through doping with polyethylene imine (PEI) is reported. This current might affect the usual source/drain current regulated by the specified gate voltage and even overcome the n-type effect. To properly preserve the n-characteristics, it is suggested that the PEI thickness must be than 100 nm and the source/drain voltage is operated below 0.5 V. This approach is also feasible for printing patterned MWNT as electrodes. Thus, all-tube p- and n-type CNTFETs are fabricated and they are demonstrated to possess proper device functions. Generally speaking, these methods are relatively convenient and low cost and they can operate in the ambient environment and at room temperature.