Evidence for a Field-Independent Enhancement Factor in the Real Tunneling Potential Barrier of Nanotube Emitters

We have demonstrated evidence that: (a) a constant characteristic induced field enhancement factor (FEF) can be determined from ab initio density functional theory (DFT) calculations on carbon nanotubes; and (b) this FEF adequately describes the real tunneling barrier. We have confirmed this finding in capped (6,6) armchair, (10,0) zigzag and (10,5) single walled carbon nanotubes (SWCNTs). In all these cases, we have verified that the characteristic local induced field enhancement factor (LIFEF) does not significantly depend on the macroscopic applied field. This establishes the LIFEF as a field-independent characterization parameter for nano-emitters.