Surface films and field emission of electrons

Abstract

Experimental investigation of the cold electron emission from metals covered with thin ( ~ 10 -7 cm) tarnish films in gases shows that substantial emission ( ~ 10 5 electrons/s) can be produced by comparatively low applied electric fields ( ~ 10 4 V/cm). The results are consistent with the view that the electrons emitted are extracted from the metal substrate by the high electric field set up across the thin surface film when covered with a layer of positive ions, the presence of positive ions on the thin film being essential to the emission mechanism which follows a field law; this high emission does not occur when the thin surface tarnish film is absent. A theory based on this view is given and quantitative agreement with the experimental data is obtained. The applications of these results to the problems of the initiation of electrical discharges in general, including the electrical breakdown mechanism at high gas pressures as well as the initiation of micro-arcs at electrical contacts, are indicated. Comparison of the field emission from a mechanically polished surface with that from an electrolytically polished surface shows that the surface smoothness obtainable by the two methods of polishing can be of the same order.