A study of field emission microtriodes

Structures simulating field emission microtriodes using Spindt-type molybdenum field emission cathodes have been successfully fabricated and tested. The key triode performance parameters-transconductance, input gate capacitance, transit time, anode voltage, and anode power-are investigated. Triodes with the anode located farther than 5 mm from the cathode are limited by the high voltage and power required to keep the transit time down. Close-spaced triodes with cathode to anode space in the range of 2-20 mu m have a transit time of 4*10/sup -12/ s at 60 V; however, an optimum anode fabrication is still required. Overall, a transconductance of 0.5 mS (5 mu S/emitter) and cutoff frequency of 0.8 MHz have demonstrated. A cathode geometry is proposed which would limit the input gate capacitance to less than 0.07 pF/mm.<>