XPS ANALYSIS OF ION-BEAM-INDUCED OXIDATION OF SILICON SUBSTRATES

XPS analysis was used to characterize Si (100) targets bombarded with an O2+ beam with energies ranging between 5.00 and 0.50 keV and incident angles between O-degrees and 75-degrees. In this energy range and at normal incidence a homogeneous SiO2 layer is built up in a sequential suboxide replacement mechanism, while for bombardments at 5.00 keV and incident angles between 28-degrees and 55-degrees only a heterogeneous layer is formed. The latter contains elemental silicon, evenly spread in the altered layer, and all possible oxidized chemical states. For bombardments at high glancing angles (55-degrees-75-degrees) only a few suboxides are observed. Finally, a linear enhancement for the Si+ secondary ion yield w.r.t. the Si4+ relative concentration is found, except for verv high Si4+ level concentrations where a strong non-linear increase takes place,