DIAMOND COLD-CATHODE

Diamond cold cathodes have been formed by fabricating mesa-etched diodes using carbon ion implantation into p-type diamond substrates. When these diodes are forward biased, current is emitted into vacuum. The cathode efficiency (emitted current divided by diode current) varies from 2 x 10(-4) to 1 x 10(-10) and increases with the addition of 10(-2)-torr partial pressure of O2 into the vacuum system. Current densities of 0.1 to 1 A.cm-2 are estimated for a diode current of 10 mA. This compares favorably with Si cold cathodes (not coated with Cs), which have efficiencies of approximately 2 x 10(-5) and current densities of approximately 2 x 10(-2) A.cm-2. We believe that higher current densities and efficiencies can be obtained with more efficient cathode designs and an ultrahigh-vacuum environment.