Hot electron emission from composite metal-insulator micropoint cathodes

Abstract

Field electron emission measurements have been made on composite emitters consisting of electrolytically etched tungsten micropoint cathodes overlayed by a 40-200 nm thick layer of epoxy resin. Their emission properties include (a) an initial switch-on effect at threshold fields of approximately 10⁹ V m^-1, (b) a subsequent reversible I-V characteristic that gives a linear FN plot at low fields (or approximately=4*10⁸ V m^-1, (c) electron spectra whose FWHM and energy shift is strongly field dependent, (d) single-spot emission images. This unusual pattern of behaviour has been interpreted in terms of a hot electron emission mechanism resulting from field penetration in the dielectric overlayer. Consideration is also given to the technological significance of such composite microemitters.