Field emission of vertically aligned carbon nanotubes with various content of nitrogen

Carbon nanotube (CNT) bundles array with hexagon arrangement were synthesized by thermal chemical vapor deposition (CVD). In order to enhance field emission, we modified CNT bundles array by post-growth nitrogen plasma treatment. The characteristics of the nitrogen-doped CNT bundles were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. With increasing the plasma treatment time, the nitrogen contents of CNTs increased, but there was a limit to the nitrogen content of the CNTs. The lowest threshold electric field ( E th) of 2.3 V/μm was observed when the nitrogen content of CNTs was 4.08 at.%, which was obtained from 70 min of nitrogen plasma treatment. The result reveals that there is an optimal time of nitrogen plasma treatment for enhancing field emission.