Time-dependent density functional study of field emission from nanotubes composed of C, BN, SiC, Si, and GaN.

Field emission from various types of nanotubes is studied by propagating the electronic density in real space and time using time-dependent density functional theory. Capped (5, 5) C, BN, SiC, Si, and GaN nanotubes are considered. The GaN, SiC, and Si nanotubes were found to be significantly better field emitters than C and BN nanotubes, both in terms of current magnitude and sharpness of peaks in the energy spectra. By analyzing the electronic structure of the various systems it is seen that the nanotubes with the highest currents have electron densities that extend significantly from the nanotube in the emission direction.