Degradation of a large area field emitter: Correspondence between linearity and saturation in Fowler-Nordheim plots and unorthodox field electron emission

We present a simple model that is able to demonstrate that degradation on the morphology of a conducting Large Area Field Emitter (LAFE) may cause a kinked behavior on the corresponding ordinary Fowler-Nordheim (FN) plot, even operating at cold field electron emission (CFE) regime at finite temperature. The simulated FN plot, which is shown to be formed by two clear linear regimes, presented also saturation at high applied field limit. Importantly, we observed a nearly linear regime, even after the degradation has been started, in which spurious values of the slope characterization parameter were achieved. This feature is a strong evidence that the change in the morphology of the LAFE, during the increasing of the applied field, can lead to an unorthodox field emission. Our results show that the effective scaled barrier field, extracted from the simulated FN plot in our model, is consistent with that found in recent experiments reported in literature. Such results are a partial history and probably justify the connection between the general mechanism of LAFE's degradation and unorthodox field emission. Finally, the consequences of initial local FEF distributions on the transition from the latter nearly linear behavior to the saturation regime are discussed.