Growth and field emission properties of small diameter carbon nanotube films

Vertically aligned carbon nanotube films with diameters smaller than 5 nm, high densities up to 1012/cm2, and lengths of ∼ 5-8 μm were deposited by microwave plasma-assisted chemical vapor deposition. Experiments show that, by continuous reduction in the thickness of the iron film (i.e., ∼0.3-0.5 nm), small diameter carbon nanotubes can be achieved with diameters that ranged from 1-5 nm, and the films are comprised of both single- and double-wall nanotubes. The electron field emission properties of the films were investigated by variable distance field emission and temperature-dependent field electron emission microscopy (T-FEEM). The films showed an emission site density of ∼104/cm2 and a threshold field of 2.8 V/μm similar to multiwalled nanotubes (1.9 V/μm). In addition, they also exhibited a temperature dependence of the emission site intensity.