The oxidation of aluminum studied by sims at low energies

The adsorption of oxygen by aluminum was studied using secondary ion mass spectrometry at low primary ion energies (? 500 eV) and low primary ion fluxes (? 5 × 10¹⁰ions/cm²/sec) in an ultrahigh vacuum system. The SIMS characteristics of a cleaned aluminum surface were measured and yield changes of positive and negative ions were measured as a function of oxygen exposure. The results strongly support a model of oxygen uptake in two stages, the first monolayer equivalent being mostly incorporated into the aluminum, probably in the second layer and the next half-monolayer equivalent being superficially chemisorbed. Selection of the correct model is important in calculations of the resonances in the electronic (valence band) structure of free-electron-like metals caused by oxygen adsorption.