Simulation of field emission from carbon nanotubes using time-dependent density functional theory and the effect of nitrogen and boron doping

We investigated the mechanism of electron field emission in prestine short carbon nanotubes using ab-initio computation in isolated and periodic simulation cells. We computed the evolution of the wave functions using Time-Dependent Density Functional Theory, where we have utilized the Crank-Nicholson propagator. We found that in prestine carbon nanotubes, emitted charge tends emerge mostly from electrons that are concentrated at the nanotube tip region, unlike metallic tips. The charge beam concentrates into specific channel structures as the wave function approaches the anode. Nitrogen doping of carbon nanotubes improves emission, in line with experimental findings, and the nitrogen dopant closer to the nanotube tip produces optimal emission performance. However, the nitrogen dopant causes dispersion of the charge cloud, which might lead to wasting of the emission current. Boron doping either impedes field emission in nanotubes or produces minimal effect