Field emission triode with integrated focus electrode

We have developed a carbon-based field-emission triode capable of operating at current densities in excess of 1A/Cm/sup 2/ for extended durations. The triode composed of an array of pyramidal emitter tips formed by chemical vapour deposition (CVD) of a carbon-based materials into a silicon mold for cathode-ray tube (CRT) display application. An alternating stack of dielectric and metal layers forms an electrically separate extraction electrode (gate) and focus electrode (focus). These two electrodes give independent control of emission current and emittance of the electron beam. We verified that the optimum focus voltage and the reduction in emittance were independent of total emission current.