Analysis of bistable noise from microfabricated field emission cathodes

Field emission current fluctuations from microfabricated cathodes have been investigated. Time-correlated noise measurements and field emission electron microscope images indicate that the dominant current fluctuations are bistable in character and are emitted from a few localized sites on the cathode surface. Apertured bistable current transitions from these emission sites are often significantly larger than the percent change in total emitted current. Analysis of bistable pulse lengths has shown that the dwell time in a particular bistable emission state decays exponentially with time. Current autocorrelation measurements indicate that bistable noise at ⩽300 K is generated by adsorbates switching between emission states and not by adsorbate diffusion.