A high resolution XPS study of a complex insulator: the case of porous silicon

High resolution XPS measurements of porous silicon samples with different preparation histories are presented. Variation of photoelectron take off angle and of flood gun conditions leads to the separation of emission of near surface electrically insulated material from substrate silicon emission. Variation of the charging level produces differential shifting in the energies of emission of the porous silicon component, which shows a balance of elemental and oxidised silicon related to preparation conditions. The systems studied display a sharp division between highly homogeneous well earthed elemental silicon and stable charged regions, and provide thus an example of the separation of spectra from a complex insulator-on-support system into individual components.