Fabrication of field-emitter arrays for inductive-output amplifiers

Summary form only given. Field-emitter arrays (FEAs) are being fabricated for X-band inductive-output amplifiers, such as Twystrodes and Klystrodes. The pre-bunched electron beam supplied by a gated FEA cathode provides smaller size, increased efficiency, and faster turn-on compared to a thermionic-cathode tube. For this application, the FEAs must supply beam currents on the order of 80-100 mA and be designed so that the microwave input drive signal can be efficiently coupled to the modulating gate of the FEA. The Lincoln FEAs are fabricated using laser-interferometric lithography, which has provided high yields of Mo-tip arrays having 0.32-/spl mu/m tip-to-tip and 0.08-/spl mu/m gate-to-tip spacings. These small dimensions reduce the gate modulation voltage that is required for suitable beam modulation and improve the high-frequency performance; they represent the smallest dimensions and highest density yet reported for FEAs. Improvements in fabrication technology, testing methods, and conditioning techniques are presented that have resulted in emission currents as high as 22 mA from one quarter of an FEA cathode. The measured input impedance agrees well with theory and can be matched by appropriate techniques.