Massively parallel arrays of single walled carbon nanotubes (SWNT) have attracted significant research interests because of their ability to (i) average out inhomogeneities of individual SWNTs, (ii) provide larger on currents, and (iii) reduce noise to provide higher cutoff frequency for radio frequency applications. However, the array contains both metallic and semiconducting SWNTs and the presence of metallic nanotube in an aligned array negatively affects the device properties. Therefore, it is essential to selectively remove metallic nanotubes to obtain better transistor properties. It was recently found that although such a selective removal can be effective for a low density array, it does not work in a high density array and lead to a correlated breakdown of the entire array giving rise to a nanofissure pattern. In order to obtain a deeper understanding of such a correlated SWNT breakdown, we studied the breakdown power in the successive electrical breakdown of both low ( < 2 /um) and high density ( > 10 /um) SWNT arrays. We show that the breakdown voltage in successive electrical breakdown increases for low density array while it decreases for high density arrays. The estimated power required for the breakdown remains constant for low density arrays while it decreases for high density arrays in successive electrical breakdowns. We also show that, while a simple model of parallel resistor network can explain the breakdown of low density array, it cannot explain the behavior for the high density array implying that the correlation between the closely spaced parallel nanotubes plays a big role in the successive breakdowns of the high density SWNTs.

Organic field-effect transistors (OFETs) have attracted tremendous attention due to their flexibility, transparency, easy processiblity and low cost of fabrication. High-performance OFETs are required for their potential applications in the organic electronic devices such as flexible display, integrated circuit, and radiofrequency identification tags. One of the major limiting factors in fabricating high-performance OFET is the large interfacial barrier between metal electrodes and OSC which results in low charge injection from the metal electrodes to OSC. In order to overcome the challenge of low charge injection, carbon nanotubes (CNTs) have been suggested as a promising electrode material for organic electronic devices. In this dissertation, we study the effect of carbon nanotube (CNT) density in CNT electrodes on the performance of organic field effect transistor (OFETs). The devices were fabricated by thermal evaporation of pentacene on the Pd/single walled CNT (SWCNT) electrodes where SWCNTs of different density (0-30/um) were aligned on Pd using dielectrophoresis (DEP) and cut via oxygen plasma etching to keep the length of nanotube short compared to the channel length. From the electronic transport measurements of 40 devices, we show that the average saturation mobility of the devices increased from 0.02 for zero SWCNT to 0.06, 0.13 and 0.19 cm2/Vs for low (1-5 /µm), medium (10-15 /µm) and high (25-30 /µm) SWCNT density in the electrodes, respectively. The increase is three, six and nine times for low, medium and high density SWCNTs in the electrode compared to the devices that did not contain any SWCNT. In addition, the current on-off ratio and on-current of the devices are increased up v to 40 times and 20 times with increasing SWCNT density in the electrodes. Our study shows that although a few nanotubes in the electrode can improve the OFET device performance, significant improvement can be achieved by maximizing SWCNT/OSC interfacial area. The improved OFET performance can be explained due to a reduced barrier height of SWCNT/pentacene interface compared to metal/pentacene interface which provides more efficient charge injection pathways with increased SWCNT/pentacene interfacial area.