Comparison of parameters for Schottky and cold field emission sources

Total energy distribution (TED) measurements were carried out for point electron sources operating in the cold field (T = 300 K) and Schottky (T = 1800 K) emission regimes. The full width at half maximum (FWHM) values of the TED's for both emission regimes were found to increase significantly above the respective theoretical values as the emitter radius (a) was decreased and as the angular current density (I') was increased. This increase in the FWHM arises from the stochastic electron-electron interactions in the beam commonly known as the Boersch [Z. Phys. 139, 115 (1954)] effect. A method was devised to extract the magnitude of the Boersch effect from the experimental TED's. The TED's were investigated as a function of P and a. In addition, the reduced brightness for both emitters was calculated from the virtual source size and I' values as a function of the FWHM values. (c) 2006 American Vacuum Society.