The stability of the CNT/Ni field emission cathode fabricated by the composite plating method

A novel composite plating method has been developed for the fabrication of carbon nanotube/Ni (CNT/Ni) field emission cathode. The field emission properties of the initial CNT/Ni field emitter show a low turn-on electric field Eon of about 1.1 V/μm with an emission current density of 1 μA/cm2, and a low threshold electric field Eth of about 1.7 V/μm with an emission current density of 1 mA/cm2. After performing a stability test with a high emission current density in high vacuum, the corresponding microstructure and the degree of graphitization of the CNT/Ni field emitter were measured by using scanning electron microscopy and Raman spectroscopy. We found that the degree of graphitization slowly decreases with the duration time tFE of the stability test, the size of small rod-like CNT/Ni composite structures in the film increases with tFE, and obvious cracks appear in the film as tFE is larger than 60 h. The degradation of the field emission properties may be explained by the Joule heating effect on the CNT/Ni field emitter under high emission current density.