EFFECTS OF VACUUM CONDITIONS ON LOW-FREQUENCY NOISE IN SILICON FIELD-EMISSION DEVICES

The effects of pressure on emission current noise have been studied. F ield emission currents from 50x50 arrays and single emitter silicon de vices were observed over a range of pressures. The current fluctuation s were analyzed in both the time and frequency domain. Signal to noise ratios between 0.9 and 6.9 were observed and appear to be more depend ent on operation time and current than on pressures. At higher pressur es, emission currents are reduced and the current is cut off completel y above a threshold pressure which is somewhere in the 10 a of Torr. P lasmas were observed in the mTorr range. The total current from a 50x5 0 tip array was measured to be only one order of magnitude greater tha n that for a single tip, suggesting that only 4-10 of the emitters in the array were functional. Spectral density coefficients of low freque ncy measurements range from 1.37 to 1.81. Some pressure dependence is suggested in the lower pressure ranges. The single emitter exhibited b urst noise with a cutoff frequency of about 10 Hz. (C) 1997 American V acuum Society.