Research On The Field Emission Properties Of Nitrogen Doped Carbon Nanotubes

Since their discovery by Iijima in 1991, carbon nanotubes (CNTs) have attracted attention of scientists from all over the world. Many efforts have been devoted to the preparation and characterization of these quasi one-dimensional structures. Previous studies on the properties of CNTs demonstrated the promising potential applications, including nanoscale optoelectronic and photonic devices, field effect transistor, field emission devices, hydrogen storage, and sensors for biological and chemical systems. Of these areas, field-emission-based flat-panel display is the closest to realizing the first commercial application. Compared with conventional metallic field emission tips, CNTs as field emission electron source have many advantages: unusually high aspect ratio (long tube length and small curvature radius on the tip), high chemical stability, low extracting field, high current density, and long operating time as well. In fact, large arrays of well-aligned CNTs can be grown by chemical vapor deposition on patterned substrates, and recently, CNT-based FEDs have been fabricated.Most field emission studies on CNTs are performed by the Fowler-Nordheim (F-N) tunneling theory, which is successful in describing the field emission of micro-sized metallic tips. F-N tunneling theory suggests that CNT field emission process includes two steps: electrons transporting along CNT body to its tip and electrons emitting from the tip by tunneling through the surface potential barriers. However, some experiments reveal that the field emission mechanism of CNTs, which shows nonlinear I-V characteristics of the F-N plots at high current range, is quite different from that of the conventional metallic tips. The intrinsic mechanism of CNTs field emission is more complicated and needed for further investigation.Despite the latest development of nanotechnologies, gaining a detailed understanding of nanoscale materials remains to be a challenge. Simulation became definitely necessary because of the restriction of experimental conditions. As for the theoretical investigations, several groups have reported the electronic structures of CNTs and localized states on CNTs tips. The geometrical and quantum size effects on CNTs field emission properties are also investigated. The emission currents of various...