Porous silicon structure studied by nuclear magnetic resonance

We present a nuclear-magnetic-resonance (NMR) study of the structure of porous silicon. Cross-polarization-magic-angle-spinning ²⁹Si NMR shows that the silicon crystalline structure is preserved in porous silicon and that there are three protonated silicon species at the surface, which are tentatively identified as belonging to different faces. The occurrence of different environments for the surface protons is supported by the heterogeneous ' H NMR line. HF and SiF₆^2- species were detected by ¹⁹F NMR in the electrolyte left in the pores.