The role of dc current limitations in Fowler–Nordheim electron emission from carbon films

We investigated the electron field emission characteristics of carbon films deposited by filtered cathodic vacuum arc. A special sandwich structure was created using alternating layers of carbon and aluminum. This structure allows both field emission and dc current–voltage characteristics to be measured on the same film. The emission current was found to follow the Fowler–Nordheim law below a critical field, Ecri. Above Ecri, the current deviates from the Fowler–Nordheim law but follows the dc current–voltage characteristics of the film. It is concluded that the frequently observed deviation of electron emission from the Fowler–Nordheim law at high field is due to the current limitation of the resistive carbon film. The important implication of this finding for device fabrication is discussed.