A low-energy electron spectrometer using concentric hemispheres and a grid retarding field

Abstract

An improved low-energy electron spectrometer using concentric hemispheres with a grid retarding field is presented. Emphasis is given to the means by which a triple-cylinder electrostatic lens, with the middle potential higher than the outer potentials, can perform a preselection. This improves simultaneously the collection efficiency and the intrinsic signal-to-noise ratio of the spectrometer. The operating mode of both the input lens and hemispheres is invariable over the energy range 0-1500 eV. The comparison of Auger transition probabilities is therefore possible. The variations of the relative collection efficiency and instrumental broadening as functions of the detection energy inside the deflectors are shown on characteristic curves. Good-quality Auger spectra of molybdenum and silicon carbide are given as examples on the electron distribution curves N(E)=f(E), obtained with a very small current density (10-3 A cm-2) at relatively low primary energy (1500 eV).