Investigations of the composition of macro-, micro- and nanoporous silicon surface by ultrasoft X-ray spectroscopy and X-ray photoelectron spectroscopy

•Nano, meso and macroporous silicon layers were obtained.•Electron structure and phase composition of the surface layers in porous silicon were investigated starting from the surface and into the bulk.•Analysis of the X-ray emission spectra applying the simulation method allowed to follow the trends in the changes of the composition between the samples of porous silicon with different pores size. The features of atomic and electron structure and phase composition of the surface in the samples of macro-, micro- and nanoporous silicon and their changes with depth were investigated with the use of X-ray photoelectron spectroscopy, ultrasoft X-ray emission spectroscopy and scanning electron microscopy. Analysis of the X-ray emission spectra applying the simulation method allowed to follow the trends in the changes of the composition for the investigated samples starting from the surface and into the bulk and to show the differences in the phase composition between the samples of porous silicon with different pores size.