Comparison of different methods in microstructural characterization of porous silicon

Results obtained using the Brunauer-Emmett-Teller method, small-angle x-ray scattering and wide angle x-ray diffraction in the study of porous silicon are compared. The BET method seems to fail when the porosity of samples is smaller than 50%, giving unrealistically large values for the specific surface area, but giving results similar to SAXS when the porosity is larger than 50%. In the comparison of the WAXD and SAXS data quite large differences between the average particle size and chord length were observed in low-porosity samples. The possible origin of the differences is discussed.