INVESTIGATION OF THE ENERGY DISTRIBUTION OF BACK-SCATTERED ELECTRONS IN THIN METAL LAYERS

Abstract

In a continuation of an earlier investigation on the back-scattering of electrons ln thick layers, the energy distribution of back-scattercd electrons in thin gold, nickel, and aluminum layers (0.1 to 0.6 mg/cm/sup 2/) was determined at an initial electron energy of 25 kv. The electrons impinged perpendicularly on the scattering foil. The Lenard opposing field method was usced, which was however improved by superposing a small alternating current voltage with an opposing voltage and by amplifying the alternating current component of the initial current with a resonance amplifier. The curve of the energy dlstribution of the back-scattered electrons was obtained directly. The curve shows a continuous pattern which extended from the primary energy up to very small energies. With decreasing layer thickness the numbcr of electrons back-scattercd with the greater energy loss decreased, the number of the fastest did not change. The curve maximum was strongly marked at small layer thicknesses and was displaced in aluminum and nickel to higher energies. In gold its position remained independent of the layer thickness in the range investigated. (tr-auth)