| This dissertation presents the synthesis and assembly of aligned carbon nanotubes, and their applications in both nano-electronics such as transistor and integrated circuits and macro-electronics in energy conversion devices as transparent conducting electrodes. Also, the high performance chemical sensor using metal oxide nanowire has been demonstrated.;Chapter 1 presents a brief introduction of carbon nanotube, followed by discussion of a new synthesis technique using nanosphere lithography to grow highly aligned single-walled carbon nanotubes atop quartz and sapphire substrates. This method offers great potential to produce carbon nanotube arrays with simultaneous control over the nanotube orientation, position, density, diameter and even chirality.;Chapter 3 introduces the wafer-scale integration and assembly of aligned carbon nanotubes, including full-wafer scale synthesis and transfer of massively aligned carbon nanotube arrays, and nanotube device fabrication on 4 inch Si/SiO2 wafer to yield submicron channel transistors with high on-current density ∼ 20 muA/mum and good on/off ratio and CMOS integrated circuits. In addition, various chemical doping methods for n-type nanotube transistors are studied to fabricate CMOS integrated nanotube circuits such as inverter, NAND and NOR logic devices. Furthermore, defect-tolerant circuit design for NAND and NOR is proposed and demonstrated to guarantee the correct operation of logic circuit, regardless of the presence of mis-aligned or mis-positioned nanotubes.;Carbon nanotube flexible electronics and smart textiles for ubiquitous computing and sensing are demonstrated in chapter 4. A facile transfer printing technique has been introduced to transfer massively aligned single-walled carbon nanotubes from the original sapphire/quartz substrates to virtually any other substrates, including glass, silicon, polymer sheets, and even fabrics. The characterization of transferred nanotubes reveals that the transferred nanotubes are highly conductive, transparent, and flexible as well. Based on transferred nanotube arrays on fabric, we have successfully demonstrated nanotube transistors with on/off ratios ∼ 105, and chemical sensors for low-concentration NO2 and 2,4,6-trinitrotoluene (TNT).;In Chapter 5, I present the study of transparent conductive thin films made with two kinds of commercial carbon nanotubes: HiPCO and arc-discharge nanotubes. These films have been further exploited as hole-injection electrodes for organic light emitting diodes (OLEDs) on both rigid glass and flexible substrates. Our experiments reveal that films based on arc discharge nanotubes are overwhelmingly better than HiPCO-nanotube-based films in all the critical aspects, including the surface roughness, sheet resistance, and transparency. The optimized films show a typical sheet resistance of ∼160O/□ at 87% transparency and have been successfully used to make OLEDs with high stability and long lifetime.;Lastly, I present the fast and scalable integration of nanowire chemical sensors with micromachined hotplates built on SiN membranes. These hotplates allowed nanowire chemical sensors to operate at elevated temperatures in order to enhance the sensitivity of chemical sensors to target gases. By applying different current through the platinum heating filament, we can easily vary the device temperature from room temperature to 350°C. These nanosensors with integrated hot plates have been exploited for the detection of ethanol, CO and hydrogen down to concentrations of 1 ppm, 10 ppm and 50 ppm, respectively. |
