Effects of high‐intensity electron bombardment on the secondary‐emission characteristics of a MgO/Au‐cermet film

摘要

An experiment to determine the durability of a 75 MgO/25 Au‐cermet film secondary‐emission cathode has been carried out over a period of 4000 h. A 2‐keV electron beam of 2 A/cm2current density was applied to a single spot and the secondary‐electron‐yield curve was monitored at regular intervals. To determine changes in chemical composition, Auger analysis was carried out with the same electron beam. Results of these tests indicated a decrease in maximum yield from 8.4 to 3.7 and a corresponding increase in the first crossover energy of 16 to 25 eV. Inspection of the relative intensities of the Auger spectral lines revealed that both Au and Mg increased relative to 0, with the Au line showing a steady increase during the first 500 h and then leveling off after 1500 h for the remainder of the testing period. The discovery of an apparent Au deficiency in the outer layers of the film is in accord with the initially high yield and the expected differential sputtering effects during argon sputter etching prior to the experiment. A surface profilometer measurement indicated that a crater of approximately 500 A˚ in depth was etched during the bombardment.