Lifetime and stability of diamond field emission devices

We present here the results of tests that measure the lifetime of carbon co ld cathodes and determine what conditions limit the lift: of the cathode. C athodes were tested in vacuum chambers using different gas environments as well as in sealed and fettered glass envelopes. We measured a projected emi ssion current half-life of 6,900 h under a constant voltage and expect this to improve to 10,000 h or more. The presence of oxygen decreased the life of the cathode by a factor of five, while the presence of water decreased t he life of the cathode by a factor of 20 or, more. After removing the gases , the decay rare was restored to near the original value. The presence of h ydrogen gas has little or no effect on the life of the cathode.