Influence of air exposures and thermal treatments on the secondary electron yield of copper

The variation of the secondary electron yield (SEY) of sputter-cleaned oxygen-free high-conductivity copper has been studied as a function of air exposure duration at room temperature. After short air exposures of some seconds the maximum SEY (δ_max) of clean copper is reduced from 1.3 to less than 1.2, due to the oxidation of the copper surface. Prolonged air exposure increases the SEY steadily until, after about 8 days of atmospheric exposure, δ_max is higher than 2. Air exposures at higher temperatures have been found to be effective in reducing the SEY of technical copper surfaces. A 5 min air exposure of copper at 350 °C followed by a 350 °C bakeout under vacuum reduces δ_max to about 1.05, which is lower than the value of pure copper and that of Cu₂O. © 2000 American Vacuum Society.