Low noise and stable emission from carbon nanotube electron sources

Remarkably stable and low noise field-emission electron sources have been obtained using individual carbon nanotubes. The maximum current fluctuation observed over 1h was merely 0.5% and the emission frequency spectrum exhibited 1∕f behavior over a bandwidth of 0.1–25Hz, above which the shot-noise limit was reached. The average noise percentage was determined to be 0.08% (i.e., a signal-to-noise ratio of 1250) for seven CNT emitters operated at several current levels. The influence of the vacuum level was also investigated.