Nanopores in Macroporous Silicon

Macroporous silicon is studied by IR absorption spectroscopy, x-ray diffraction, and the electron–positron annihilation method in comparison with single-crystal Si (substrate), polycrystalline Si (powder), anda-SiO₂ (silica glass). According to IR absorption data, as-prepared macroporous silicon contains a significant amount of oxidized material. Annihilation spectra of macroporous silicon attest to the presence of a system of nanopores, in which positronium atoms are likely to localize. Diffraction patterns reveal considerable amounts of silicon particles oriented at random. Both the polycrystalline phase and nanopores reside on the surface of macropores.