Improvement of field-emission-lamp characteristics using nitrogen-doped carbon nanocoils

• Uniform carbon nanocoils can be grown at 600 °C using a polymer-palladium catalyst.
• The field emission characteristics of CNCs were enhanced by a N2 post-treatment.
• The nitrogen content could reach 4.9 wt.% in the nitrogen-treated CNCs.
• N atoms increased sp2 clusters and reduced turn-on voltage from 2.1 to 1.4 V/μm.
• β value increased from 2465 to 3241 from as-grown CNC emitters to N-doped ones.

Carbon nanocoils (CNCs) synthesized using thermal pyrolysis chemical vapor deposition on 304 stainless steel wire substrates were used as the cathodes of field emission lamps (FELs). The effects of the growth temperature on the FE performances were studied, and we observed that uniform and dense CNCs that are suitable for use as FE cathodes can be synthesized at 600 °C. We also found that a nitrogen doping post-treatment can significantly improve the FE efficiency of the CNCs. When doped at 200 °C with a nitrogen flow rate of 500 sccm for 30 min, the nitrogen content of the CNC surface could reach 4.9 wt.%. ESCA analysis indicates that the doped nitrogen atoms formed CNx bonding and increased the sp2 clusters in the CNCs. The turn-on voltage was reduced from 2.1 V/μm to 1.4 V/μm, and the β value increased considerably from 2465 to 3241 after N-doping post-treatment. The bulb-type FELs using our N-doped CNC cathodes showed a good luminous efficiency as high as 75 lm/W at 8 kV.

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