Erhöhung der Feldelektronen-Emission von Wolframspitzen durch Aufdampfen von Beryllium

The mean work function of tungsten determined from Fowler-Nordheim plots can be reduced from 4.5 to 2.5 eV by depositing a thin layer of evaporated beryllium and subsequent thermal treatment at 800 °C in a vacuum of 10^?7 to 10^?10 Torr. Electron and ion field emission patterns of tungsten tips with and without beryllium demonstrate the effect of the beryllium deposit. For an application of the tungsten tips with beryllium, the excellent stability and the high emissivity at low voltages are of interest.