| In this dissertation, I present my development of an innovative approach to utilize the advantage of the stable semiconducting properties of two materials, carbon nanotube thin film and indium gallium zinc oxide thin film to form circuits operating in complementary mode. The approach has resolved the following issues. Firstly, carbon nanotube (CNT) thin film transistors (TFTs) behave as p-type transistors in ambient with high work function metal electrodes, such as palladium. And CNT TFTs exhibit desirable transistor behavior showing device mobility and on-current density suitable for macroelectronic applications, which is superior to the commercially available amorphous silicon TFTs. However, in order to operate circuits with low steady-state power dissipation, it is more desirable to have complementary circuits, meaning circuits consisted of both p-type and n-type transistors. CNT TFTs can be converted into n-type, however, there has not been a method to realize n-type CNT TFTs with long term stability. On the other hand, oxide semiconductor TFTs have been well-known high performance n-type TFTs. However, researchers have also struggled to obtain stable and high performance p-type oxide semiconductor TFTs. I demonstrate using CNT TFT, the stable p-type device, and indium gallium zinc oxide (IGZO) TFT, an outstanding n-type device to realize integrated circuits operating in complementary mode with good stability in ambient. I have demonstrated for the first time a large-scale integration of CNT/IGZO hybrid circuits, manifested in a 501-stage ring oscillator comprised of over 1000 TFTs, showing the high yield property of both of the p-type and the n-type devices and their stability in ambient environment. This hybrid complementary design enables circuits to operate with low static power consumption, and allows the output of the circuit to reach rail-to-rail voltage. In addition, in order to further improve the stability of the device, I introduce a method to reduce the hysteresis in CNT TFTs, by encapsulating the devices with a layer of photoresist. Further, I was able to demonstrate this is a generic approach.;In addition to carbon nanotubes, I also present my study in the controlled synthesis of silicon nanowires, another promising nanomaterial that can be used for energy storage device. I demonstrated the bulk synthesis method to increase the throughput for the nanowire growth. High throughput of silicon nanowire is desirable for applications such as Li-ion battery.;My dissertation is divided in five chapters. Firstly, the Introduction chapter gives a brief explanation on the electrical properties of carbon nanotube thin film transistors; then it discusses macroelectronics, an important technology for modern consumer electronics, and it explains how CNT TFT can play an important role in the development of macroelectronics, hence the motive for intensive research in the field of CNT thin films. Secondly, the idea and the development of the large-scale hybrid integrated CNT/IGZO TFTs for macroelectronic applications are discussed in chapter 2. Thirdly, a systematic study on the method to improve the stability of CNT TFTs is presented in Chapter 3. The hysteresis of CNT TFTs can be controlled with appropriate passivation of the CNT TFTs. In the 4th chapter, a novel method to improve the yield of silicon is introduced. And a lithium ion battery half-cell was realized using the as-grown silicon nanowires with this bulk synthesis scheme. Finally, I conclude my dissertation and also present my idea for the future development of the CNT-based macroelectronics. The idea is to use CNT TFT for fully transparent touch screen applications. |
