Electron Bombardment Effects in Thin Dielectric Layers

Abstract

Dielectric layers of mica, Pyrex, arsenic sulphide and antimony sulphide, between 0.7 and 4μ thick, have been investigated under electron bombardment with electron energies up to 50keV. The specimens carry evaporated Al electrodes, which are practically transparent to the primary electrons. The results include transmission curves for the primaries; the range values are in agreement with the Thomson-Whiddington law. With both electrodes at the same potential a steady secondary current begins to flow to the bottom electrode when the bombarding electrons have penetrated about half the specimen. Experimental values of primary and secondary currents for specimens of different thickness and dielectric fall on common curves when plotted against a suitable independent variable. The secondary current is shown to depend on the absorbed energy. Results for mica with applied fields up to 106 vcm-1 across the specimen are included. An interpretation of the secondary current curves is given in terms of the displacement of charge carriers in the space-charge field within the dielectric