Evaluating the effect of surface workfunction variability on metal emitter array current and emittance for high power devices based on a patchwork model

Abstract Evaluations of the current output from metal emitter arrays with a hexagonal lattice arrangement are carried out based on kinetic simulations. Geometric field enhancements with shielding and the presence of workfunction ( φ ) variations are included. Electron emission is treated using modified field emission theory, with φ variability based on a simple patchwork model. Results for arrays with different numbers of metal emitters show that for a given mean φ value, the greatest currents result for structures having the largest variability. Furthermore, it may be desirable to incorporate φ fluctuations in cathodes at the central zone of emitter arrays to mitigate screening effects and enhance currents. The results also indicate lowest emittance in the case of cathode surfaces with minimal φ variability. As the chosen technique is general, related aspects such as heating effects, a more comprehensive electro-thermal model of electron emission, or Wigner-based electron cathodic transport for a more complete analysis of photoemission could be included in future work.