Abstract
Carbon nanotubes, known as one-dimensional (1D) nanostructures, have drawn much attention in recent years and their electron structure can be changed by gas adsorption, surface modification and heteroatom injection. The current applications however often focus on bundled carbon nanotubes, such as flexible, transparent and conducting films are made by coatings of carbon nanotubes onto plastic substrates. Carbon nanotubes can also be used as reinforcing fillers to improve electrical and thermal properties of polymer composites. In this thesis, gas sensors are fabricated by aggregated nanotubes to probe charge transfer between tubes and sensing mechanism is verified by ab-initio calculations. Furthermore, we synthesize nitrogen-doped carbon nanotube to create on-tube Schottky junction devices. Chapter 1 introduces the background and property of carbon nanotubes, surface modification for carbon nanotube and the simulation system. Chapter 2 describes experimental setups、characterization techniques and simulation methods. Chapter 3 discusses the oxygen sensing mechanism of carbon nanotubes. In this work, devices are fabricated by carbon nanotubes arranged in different fashions with respect to electrodes. Electrical measurements reveal intercalated molecules acting as charge carriers between tubes. Ab-initio calculation supports dynamic intercalation and charge transfer through bouncing of O2 between tubes. Chapter 4 aligned multi-walled CNTs are built to exhibit diode behavior by N2 plasma treatments. Surface modification for carbon nanotubes is studied by material analysis and ab-initio calculation. The simple fabrication of device without lift-off process is provided, and the parallel combination of a bundle of CNTs can promote output current. Chapter 5 concludes the experimental results.