Analysis of isotropic and anisotropic etch field emitter array cathodes

Summary form only given, as follows. The paper summarizes computer modelling and numerical results on two field emitter array (FEA) cathode designs manufactured by MCNC. DEMEOS, a deformable triangular mesh finite element gun code, which includes a Fowler-Nordheim model of emission as an option, was used to perform the analysis. This code can include curved dielectrics and irregular shaped tips. Further, the variable mesh feature enables a whole tip and gate structure to be analyzed expeditiously in a single computer run. An isotropically etched tip design was analyzed as well as an anisotropically etched tip design. Experimental and calculated results compare quite well for the isotropic design for which there is much experimental data. It was found and verified experimentally that the isotropic tip has a lower turn-on voltage than the flatter faced anisotropic tip. On the other hand, the beam emerging from the anisotropic tip has significantly lower angular divergence which is important in FEA cathodes contemplated for use in linear beam microwave tubes.