Field emitter array cathodes for high current density, high current applications

Summary form only given. Microfabricated field emitter array (FEA) cathodes have demonstrated the potential to provide kA/cm/sup 2/ current densities with long lifetimes in continuous or repetitively pulsed modes of operation. However, FEA cathodes have historically not achieved their full potential due to imperfect spatial uniformity of emission. For example, they have produced current densities of 2 kA/cm/sup 2/, but only over cathode areas of approximately 10/sup -4/ cm/sup 2/. On the other hand, areas of 10/sup -1/ cm/sup 2/ have reliably demonstrated current densities of only /spl sim/1 A/cm/sup 2/ due to, at least in part, less than ideal emission uniformity. We are addressing this issue with an in situ cathode processing technique that has been shown to both clean emitter tips and dramatically improve the spatial uniformity of emission. With additional effort the technique can likely be developed into a dependable process for achieving uniform emission between the tips of FEA cathodes and facilitate reliable FEA operation at high current densities and high total currents. To date we have used the processing technique to demonstrate an emission current of 300 mA from a 50,000-tip array covering an area of 7.8/spl times/10/sup -3/ cm/sup 2/. This corresponds to a current density of 38 A/cm/sup 2/. To our knowledge, such a total emission current from single FEAs has never been reported. We believe that with continued process development these arrays will achieve total currents of 1 A at current densities exceeding 100 A/cm/sup 2/. This talk will summarize the results of our cathode processing studies and discuss possible avenues of future research to enhance FEA performance.