Oxidation of aluminum studied by secondary electron emission

The electron emission yield is measured for impact of 3 keV electrons on polycrystalline aluminum, which is exposed to oxygen. At different oxygen gas pressures the yield is measured as a function of time. The oxygen pressure is in the range between 2 x 10(-9) and 3 x 10(-6) mbar. It is found that the yield depends not only on oxygen exposure but also on the oxygen pressure. In the begin of oxygen exposure the yield decreases due to chemisorption of oxygen, but then the yield increases due to oxide formation. A model based on rate equations with adjustable parameters is proposed, which describes the oxidation process and electron emission yield. The parameters are fitted to give best agreement with the measured yield curves. The parameters include sticking coefficients and time constants of oxidation. Whenever possible, evaluated parameters were compared with published data and reasonable agreement is found. (C) 2002 Elsevier Science B.V. All rights reserved.