Research on Thin Film Tunnel Cathodes, Recombination Cathodes, and Similar Cold Cathodes. Volume I

摘要

Two cold cathodes were investigated which promised to produce useful electron emission: the thin film tunnel cathode and the recombination cathode. The experimental work on the tunnel cathode was primarily concerned with the evaluation of the usefulness of various dielectric films as tunnel barriers in metal-insulator-metal structures. Useful films must be capable of withstanding electric fields of the order of 10,000,000 V/cm and permit the passage of hot electrons. The methods for forming the dielectric films included anodization, plasma oxidation, thermal oxidation, vacuum deposition, reactive sputtering, and chemical vapor deposition. The following materials were investigated: oxides of A1, Mg, Mn, Nb, Si, Ta, Th, U, and Zr, as well as BN. The best performance in tunnel cathodes was obtained with A12O3 and BN. A transfer ratio (ratio between emitted current and circulating current) in the 0.001 range could be accomplished without special treatment of the Au top metal film in both cases. Cs deposition on A1-A12O3-Au cathodes resulted in a transfer ratio to a maximum of 8%. The most stable devices resulted from the use of BN films and permitted dc operation over several hours at diode current densities in the 10-30 A/sq cm range.