Two figures of merit for field emitters deduced from Fowler-Nordheim plots

Two factors are deduced from Fowler-Nordheim plots of field emitters, one from their slopes and the other from their slopes and intercepts. The former factor concerns the work function and local field conversion factor, and the latter concerns the emitting area. These two factors are shown to be useful as figures of merit for field emitters both theoretically and experimentally. The derivation of these two factors and an expression of onset voltage using them are presented. It is illustrated that the onset voltage gives the overall figure of merit for field emitters, whereas the two factors proposed here as figures of merit are useful for further detailed discussions for evaluating field emitters and processes to fabricate them.