Thermionic Emission of Thin Films of Alkaline Earth Oxide Deposited by Evaporation

Abstract

Monomolecular films of BaO or SrO were deposited by evaporation on clean tungsten or molybdenum surfaces with precautions to eliminate effects caused by excess metal of the oxide or by heating. Thermionic emissions of the same order of magnitude as from commercial oxide cathodes have been obtained from these systems. The results can be explained qualitatively by considering the adsorbed molecules as oriented dipoles. Although the results may suggest a possible mechanism for a portion of the emission from thick oxide cathodes, there are serious obstacles against such thin film phenomena as a complete explanation.