Field emission of electrons in discharges

Abstract

Substantial emission of 10 4 to 10 5 electrons/s was obtained from cathodes of oxidized nickel and tungsten with electric fields of about 10 5 V/cm. By relating this emission to the electric field by the Fowler-Nordheim equation, estimates of the work function and emitting area of the source of the electrons were made. It was found that the effective work function for the emitting source on oxidized nickel and tungsten was roughly 0.5 eV, and that the emitting areas were 10 -12 cm 2 . This is consistent with the view that the electrons were obtained from the oxide itself and not from the underlying metal. The presence of tarnish films and oxides on electrodes enhanced the cold electron emission greatly, and played an important part in the mechanism of electron production; the presence of metallic dust was found to enhance the emission by factors up to 10 3 . The technique used in the investigation provides a method by which a rapid assessment of the electron emissive properties of metals can be made, and is applicable to a wide variety of surfaces. While a consistent theory of the action of heavily oxidized tungsten and nickel electrodes (surface conditions often met with in practice) can be given, a further experimental investigation of the electron emission from surfaces covered with thin surface films (10 -7 cm) is necessary.