Theoretical comparison between field emission from single-wall and multi-wall carbon nanotubes

We present three-dimensional simulations of field emission from single-wall and multi-wall carbon nanotubes. The structures considered are the metallic ideally open (5,5), (10,10), (15,15) and (5,5)@(10,10)@(15,15) nanotubes. For the multi-wall structure, flat and convex terminations are considered. The scattering calculations are achieved using a transfer-matrix methodology and band-structure effects result from using pseudopotentials and repeating periodically a basic unit of the nanotubes. The electronic emission from the single-wall nanotubes considered is found to decrease linearly with the radius of the tube. Multi-wall nanotubes are better emitters than single walls, the current extracted from multi-wall structures being higher than the total current obtained by considering their single-wall layers separately. The current emitted from a multi-wall structure is still increased when the termination is convex (instead of flat). The reduced polarizability of multi-wall nanotubes (compared to single-wall structures) is an important aspect for explaining their field-emission properties.