I by anodic oxidation in aqueous KOH

The structure and composition of the passivated silicon surface by electrochemical etch-stop process is analysed using angle resolved x-ray photoelectron spectroscopy (AMPS). The passivated surface is found to be composed of a layer of stoichiometric oxide and a transition layer. The thickness of the stoichiometric oxide layer depends on the passivation conditions and the kind of doping. The transition layer is about one or WO monolayers thick in all the samples and is composed of a mixture of different silicon suboxides and probably features the presence of Si4 groups. Finally, our results are in agreement with an oxidation process controlled by the presence of holes at the silicon surface.