The noise of field emission (FE) currents ranging from 10 pA to 100 μA was measured under ∼7× 10-10 Pa. Stepwise features were routinely observed in damping curves of the FE current, indicating remarkable sensitivity of the FE current measuring system. The lowest frequency measurement of shot noise was recorded below 10 Hz. Space-charge suppression of noise was not observed for FE currents up to 100 μA. Adsorption of residual gas increased the intensity of noise and made the noise of field emission current be dominated by the flicker noise.
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