Abstract
In this study, we using the microwave plasma enhanced chemical vapor deposition (MPE-CVD) system to synthesize the carbon nanotubes, and observing the structures, chemical bonding and the field emission properties of carbon nanotubes doped by the nitrogen and boron elements. From the results of FTIR, the primary chemical bonds of C/N are single bonds. It is found that N doped carbon nanotubes using ECR-CVD and MPE-CVD can increase the sp2 bonding and decrease the sp3 bonding, which can enhance the properties of field emission. The onset voltages are decreasing from 3 V/μm to 2 V/μm, and the enhancement factor is increasing to 40 ~ 120 %. The nitrogen plasma excited by MPE-CVD has higher energy to substitute the carbon and penetrate the graphite walls. However, the nitrogen plasma excited by ECR-CVD only can treat the surface of carbon nanotubes and form dangling bond that are well to emit electrons. If the carbon nanotubes are doped by boron atoms, the sp3 bonding will increase and the onset voltages will also increase to 3 V/μm. The enhancement factor will decrease in the percentage of 35, it is because of the boron has less electrons, and electron holes will trap the electrons when emitting.