One of the most promising applications of CNTs is in field emission (FE) devices. High aspect ratio and atomically sharp radius of apex curvature of the CNTs enhance the local field and lower the threshold field for electron emission. 

The emission properties of CNTs are governed by the work function, crystalline structure, geometry of their tips, and so forth. In addition, the surrounding gases and impurities on the surface have also been known to strongly affect their FE characteristics.

Carbon nanotubes (CNTs) have been investigated as field electron emission sources for field emission displays (FEDs), cathode ray tubes(CRTs), backlights for liquid crystal displays,outdoor displays, and traffic signals, because CNTs have several suitable properties for field emitter. A number of results have been reported on the field emissions from multi-walled nanotubes (MWNTs) and single-walled nanotubes (SWNTs) synthesized by various methods. However, the commercialized device based on CNTs are very rare due to the difficulty in controlling the properties of CNTs and developing the practically efficient technology for cathode fabrication on

large area substrate. Electrophoresis was used to deposit diamond on Si emitter, and to purify and align CNTs.

For widespread use of FE it is necessary to study the possibility of achieving high emission current densities and stability of this process. Voltage-current characteristic of cold cathode in the region of prevalence of field emission current is generally described by Fowler-Nordheim formula. Detailed analysis of this model and its transition to the region of thermionic emission was carried out in.(https://systems.enpress-publisher.com/index.php/CAN/article/view/567)

References:

[1] E. Milnoux, O. Groening, K. B. K. Teo et al., “Achieving high-current carbon nanotube emitters,” Nano Letters, vol. 5, pp. 2135–2138, 2005.

[2] J. Ali, A. Kumar, S. Husain, and M. Husain, “Effect of catalyst-deposition methods on the alignment of carbon nanotubes grown by low pressure chemical vapor deposition,” Nanoscience and Nanotechnology Letters, vol. 3, no. 2, pp. 175–178, 2011.

[3] Javid Ali, Avshish Kumar, Samina Husain, Shama Parveen, Renu Choithrani, Mohammad Zulfequar, Harsh, Mushahid Husain, "Enhancement of Field Emission Properties of Carbon Nanotubes by ECR-Plasma Treatment", Journal of Nanoscience, vol. 2014, Article ID 437895, 5 pages, 2014.