Anodic oxidation of porous silicon bilayers

This paper focuses on the study of the effect of anodic oxidation in porous silicon bilayers composed of two porous layers of different porosities. Th e order of the two types of layers has been alternated, and the thicknesses and refractive indices have been optically characterized by Fourier transf orm infrared spectroscopy. The results show that the refractive index of an odic oxidized porous silicon is reduced significantly with respect to just formed porous silicon. It is also observed that the quality of the oxidatio n is related to the porosity of the inner porous layer of the silicon bilay er structure. This effect is interpreted in terms of quantum size effects. (C) 1999 Published by Elsevier Science B.V. All rights reserved.