A hybrid approach to modelling large area field emitters

Abstract

Large area field electron emitters, typically consisting of several thousands of nanotips, pose a major challenge since numerical modeling requires enormous computational resources. We propose a hybrid approach where the local electrostatic field enhancement parameters of an individual emitter is determined numerically while electrostatic shielding and anode-proximity effects are incorporated using recent analytical advances. The hybrid model is tested numerically on an ordered arrangement of emitters and then applied to recent experimental results on randomly distributed gold nanocones. Using the current-voltage data of two samples with vastly different emitter densities but having similar nanocone sizes, we show that an appropriate modeling of the emitter-apex together with the analytical results on shielding and anode-proximity effects, leads to consistent results for the apex radius of curvature. In both cases, the $\text{I-V}$ data is approximately reproduced for $R_a \simeq 9$nm. Importantly, it is found that anode-proximity plays a significant role in counter-balancing electrostatic shielding and ignoring this effect results in the requirement of a much smaller value of $R_a$.