A NEW PERSPECTIVE ON THE HOT-ELECTRON EMISSION FROM METAL-INSULATOR MICROSTRUCTURES

A combination of a high resolution electron spectrometer and a field emission microscope has been used to study the field emission of electrons from composite metal-insulator micropoint cathodes. These emitters consist of similarly prepared electrolytically etched metallic tungsten micropoints (M), covered with layers of several types of dielectric materials (I). These dielectrics include alumina, hydrocarbon, plastic, lacomit and resin. Some of the dielectric coatings used gave an opaque form which did not make it possible to measure their thicknesses. Other dielectrics produced a measurable regular layer with thicknesses varying from 0.04 to 0.2 μm. Those produced reversible current-voltage characteristic that gives a linear FN plot at low fields (≲ 108 V m) and a saturated emission at high fields ≳ 4 × 10 V m, emission images and electron spectra of both thin and the optimum thick coatings. The observed effects, e.g. the threshold switch-on phenomena and the field-dependence of the FWHM and energy shift of the electron spectra have been identified in terms of a hot-electron emission mechanism resulting from field penetration into the insulating film where conducting channels are formed. Evaluation of the technological importance of such devices as practical electron source is given. These experimental and theoretical findings will be shown to be consistent with recent published analysis of M-I-V systems. © 1990.