Resolution and Sensitivity of the Spherical-Grid Retarding Potential Analyzer

The resolution and sensitivity of the spherical-grid retarding potential difference electron-energy spectrometer are discussed. The resolution is shown to be determined by lens effects at the second grid and to be proportional to the ratio of the grid separation to the grid mesh hole size. The resolution of three experimental systems is discussed and shown to be in agreement with the results of computer analysis. The ultimate sensitivity or signal-to-noise ratio developed by the analyzer is shown to be improved by the addition of a ``postmonochromator'' collector scheme which selectively gathers those electrons which pass through the retarding field with a minimum of kinetic energy. Application of the analyzer to Auger electron spectroscopy and x-ray photoelectron spectroscopy is demonstrated. The retarding potential/postmonochromator combination is shown to possess distinct advantages in terms of simplicity and/or sensitivity for both techniques.