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 oxyg en-free high-conductivity copper has been studied as a function of air expo sure duration at room temperature. After short air exposures of some second s the maximum SEY (delta(max)) of clean copper is reduced from 1.3 to less than 1.2, due to the oxidation of the copper surface. Prolonged air exposur e increases the SEY steadily until, after about 8 days of atmospheric expos ure, delta(max) is higher than 2. Air exposures at higher temperatures have been found to be effective in reducing the SEY of technical copper surface s. A 5 min air exposure of copper at 350 degrees C followed by a 350 degree s C bakeout under vacuum reduces delta(max) to about 1.05, which is lower t han the value of pure copper and that of Cu2O. (C) 2000 American Vacuum Soc iety. [S0734-2101(00)04103-8].