Model for predicting the effects of device geometry on the capacitance of field emitter array cathodes

Successful application of field emitter array cathodes at microwave frequencies is dependent upon significant progress in emitter development. Two factors are of primary concern, namely, the transconductance and the array capacitance. To provide guidance in development of structures with minimum capacitance, a scaled, physical model of an emitter array has been developed and used to study qualitatively the effect of several geometrical and materials parameters on device capacitance. In this article the effects of an insulating versus a conducting substrate, and variation of the insulator film thickness, extractor aperture diameter, and extractor film thickness are reported. It is shown that the array capacitance is primarily determined by the details of the extractor aperture–emitter tip geometry, and is not influenced by the extractor to substrate spacing unless the insulator film thickness is substantially less than one‐half the pin‐to‐pin spacing in the array. Although the results are not intended to b...