Enhanced Field Emission Properties of CNT Film Emitters through Densification using Nitric Acid

The densification effect on field emission characteristics of carbon nanotube (CNT) film emitters made with a thin multiwalled CNT film is evaluated by changing the concentration of nitric acid. As the concentration of nitric acid used for the densification of the film increases, the thickness of the CNT film decreases while the electrical conductivity increases. The results indicate that the densification progresses further with higher concentrations of nitric acid. The decrease in the thickness of the film is due to the reduced gap between the CNT network. The electrical conductivity of the densified CNT film increases because the distance between the CNTs decreases and the contact area between the CNTs increases. The emission current of the densified CNT film emitter significantly increases, and the long-term emission stability of the emitter is also improved after densification. However, they deteriorate under 10 M nitric acid due to severe damage to the surface of the CNTs. The obtained results show that the concentration of nitric acid is a crucial parameter in determining the densification effect of the CNT films. It is suggested that densification will enhance the performance of the CNT film emitters for various field emission device applications in the future.