Evidence of pore correlation in porous silicon: An x-ray grazing-incidence study

The structure of porous silicon is investigated by grazing incidence x-ray scattering. Using GISAXS (grazing incidence small-angle x-ray scattering), a systematic pore correlation is observed for all porous silicon types.The quantitative analysis of the measurement has been performed for the p - -type sample, using a spherical model of pores and an isotropic distribution of scattering particles, leading to a typical pore size of 6.2 nm and to a particle-particle correlation length of 8.6 nm. In addition for this type of porous silicon, the morphology of the surface and interface of the layer have been studied by specular and off-specular reflectivity. The roughening due to the pore front propagation is quantified and the interface instability of p - -type porous silicon is observed.