Field emission enhancement from directly grown N-doped carbon nanotubes on stainless steel substrates

N-doped carbon nanotubes (NCNT) are grown directly on the stainless steel (SS) substrates by chemical vapor deposition at atmospheric pressure, and the field emission (FE) enhancement mechanism is investigated. The turn on and threshold fields of the NCNT emitters are 1.61 and 2.05 V mu m-1, respectively, lower than those from the CNT emitters. The improved FE properties are mainly attributed to the reductions of the work function and the surface resistance. First-principles calculations suggest that the work function of NCNT depends highly on the N doping concentration. In addition, the N-doping in CNT leads to the charge aggregation around N, benefiting the field emission enhancement. More importantly, for the CNTs, the emission current dropped by 28.6% after ~7h continuous emission at the pressure of 5.38 x 10(-4) Pa, while the current reduced only 5.8%after 7 h test at the pressure of 8.35 x 10(-4) Pa for the NCNTs, suggesting that the NCNTs exhibit better resistance to the ion bombardment in high pressure. The investigation demonstrates that the facilely grown NCNTs are promising to develop practical FE cathodes.