Auger Spectra Induced by Noble Gas Ion Impact on Magnesium, Aluminum, and Silicon.

The Auger spectra resulting from 20-200 keV Ar('+) and Ne('+) impact on Mg, Al and Si were studied. A mechanism was formulated which explains the sharp features in all three targets as due to atoms with 2p inner shell vacancies sputtered free from the solid surface. The asymmetric continuum underlying these sharp features was found to be due to 2p vacancies decaying within the bulk. A model was formulated consisting of gaussian lineshapes for the predicted atomic transitions from singly ionized and neutral initial states and an experimentally derived electron induced spectrum for the bulk contribution. The model was tested by fitting it to the spectra using a non-linear least squares curve fitting routine. All features of the spectra were completely explained by this fitting routine supporting this interpretation of the ion-induced spectra. Information deduced from the curve fitting included average sputtered atom energies, relative atomic line intensities, dependence of atomic to bulk ratios with Auger lifetimes, and experimental values for the energy of the neutral atoms with 2p vacancies. Spectra taken using different projectile energies show increased atomic to bulk ratios with projectile energy. This is opposite what would be expected from nuclear stopping power or sputtering data in this energy range.