Evidence for quantum confinement in porous silicon from soft x-ray absorption

Measurements of x-ray absorption in the vicinity of the silicon L edge in porous silicon show a blueshift and a broadening of the conduction band edge, consistent with a distribution of quantum confinement energies. The absorption spectrum for porous silicon can be fit by a broadened and energy-shifted version of the crystalline silicon absorption spectrum. The average quantum shift and broadening used in the fit to the absorption spectrum are in reasonable agreement with the corresponding parameters derived from the photoluminescence spectrum.