SECONDARY-EMISSION OF BERYLLIA ON BERYLLIUM

Thin layers of beryllia (BeO) were formed on beryllium (Be) substrates by oxygen-ion bombardment, heating beryllium in air, and by sputtering BeO. The secondary yield (from both secondary and backscattered electrons) was measured relative to BeO thickness and the contaminants present. In good agreement with Ritz et al. [1], the carbon content substantially reduces the yield and an expression was introduced to estimate the effect of other low-yield participants. Also in good agreement with Bronshteyn et al. [2], the voltage for highest yield increased with BeO thickness, the yield versus voltage curves were also shown to be dependent on BeO thickness and exhibited sharp maxima. At greater thicknesses, surface voltage charging was suspected but investigations showed that this was not the case.