Small-angle X-ray scattering study of the microstructure of highly porous silicon

Small-Angle X-ray Scattering is well suited to the study of porous silicon microstructure since the pore radii range (2-10 nm) corresponds to the small-angle scattering range (1-100 nm). In all the studies realized till now, the porous silicon layers were always supported by the substrate. Recently, it has been possible to detach the porous silicon layer from the substrate. We performed small-angle X-ray scattering measurements, on such P-type samples, at a synchrotron radiation source. Close to the origin, the scattering pattern shows an anisotropic behaviour when tilting the sample surface with respect to the X-ray beam. This anisotropy is different from the one observed previously in the case of P + samples