Effects of vacuum conditions on low frequency noise in silicon field emission devices

The effects of pressure on emission current noise have been studied. Field emission currents from 50x50 arrays and single emitter silicon devices were observed over a range of pressures. The current fluctuations 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 dependent on operation time and current than on pressures. At higher pressures, emission currents are reduced and the current is cut off completely above a threshold pressure which is somewhere in the 10 a of Torr. Plasmas were observed in the mTorr range. The total current from a 50x50 tip array was measured to be only one order of magnitude greater than that for a single tip, suggesting that only 4-10 of the emitters in the array were functional. Spectral density coefficients of low frequency measurements range from 1.37 to 1.81. Some pressure dependence is suggested in the lower pressure ranges. The single emitter exhibited burst noise with a cutoff frequency of about 10 Hz. (C) 1997 American Vacuum Society.