Theoretical Interpretation of Field Emission Experiments

Abstract

In careful experiments by Dyke and his co-workers it has been observed that the field-emission currents from tungsten and barium-on-tungsten emitters were progressively reduced below that expected from the Fowler-Nordheim law as the field was increased. These effects were attributed to electron space charges in the neighborhood of the emitters. However, if a detailed examination of the surface energy barrier is made, it is found that the barrier existing in the experiments was almost certainly different from that assumed in the derivation of the Fowler-Nordheim law. This is particularly true for the coated emitters because of the formation of barium double-layer patches, but even for clean tungsten emitters failure of the image-force "motive" within ∼3 A from the surface, as discussed by Slater and others, must occur.