High-field single electron emission rates and their influence on the Paschen characteristics in compressed gases

Abstract

By means of a newly developed statistical avalanche counting technique which enables high-field, single electron emission rates (SEERS) to be measured from unsparked freshly prepared surfaces having various thicknesses of oxide film, it is established for the first time that SEERS increases, for a given electric field, with an increase in the bulk modulus (hardness) of the material cathodes; also remarkably the thicker the oxide layer, the higher the SEERS. These trends are reflected in the Paschen sparking characteristics which show that the gaseous electric strength decreases with increase in the bulk modulus and increase of oxide layer thickness of the cathode material; and thus the increase in SEERS. This former trend is opposite to that established more than forty years ago. Other hitherto unobserved phenomena like a gas pressure effect, switching from a low to a high electron emission mode and vice versa, the influence of deliberate sparking and the total absence of spark conditioning are reported. Analysis of SEERS by the more successful Richardson-Schottky rather than the Fowler-Nordheim equation shows that the low electric field intensification factors derived increase with the bulk modulus of the cathode material and ultimately are determined by the polishing procedure.