Optical and electrical studies of a single Spindt-type field emitter

In this study, the numerical results obtained on a single Molybdenum Spindt-type emitter through electrostatic finite-element modelling, Fowler-Nordheim calculations, and electron trajectory simulation are presented. These simulation results are correlated to experimental results on electrical characteristics as well as beam intensity profile of a single tip. Electrostatic modelling of single Mo tips shows that the measured beam characteristics cannot be described without taking into account nanometric protuberances at the surface of the tip. Electric fields computed from a conical tip with a smooth surface are far lower than those which can explain the measured electronic emission. Protuberances at the apex of the tip provide a second level of amplification of the electric field and are clearly observed at the apex of the tip. Fowler-Nordheim standard theory emission parameters (emissive surface, mean electric field) extracted from current-voltage characterizations confirm that a multi-stage amplification mechanism fits with the observed current levels. The spatial distribution of the beam intensity is clearly the sum of the contributions of individual emission sites on the surface of the tip.