Field emitter-array development for microwave applications

Summary form only given. In order to make microfabricated field-emitters useful for microwave operation it is necessary to maximize the transconductance of the emitter array. The parameters that determine the transconductance are the emitter tip´s work function; the field-enhancement factor at the tip, /spl beta/ (E=/spl beta/V); and the packing density of the emitter array. The work function depends on the tip material and the condition of the tip´s surface resulting from processing and operating environment. Control of these parameters can be rather limited in practical applications. It is shown that the most direct way to increase the transconductance is by increasing the packing density of the emitter array. With emerging lithography techniques it is possible to increase the packing density by about two orders of magnitude over what was available at the start of the microwave development effort. Updated details of how these improvements have been implemented and their impact on cathode performance are presented.