SOFT-X-RAY FLUORESCENCE OF POROUS SILICON - ELECTRONIC-STRUCTURE OF SI NANOSTRUCTURES

The electronic structure of porous Si is investigated using soft-X-ray fluorescence spectroscopy. Significant changes are observed as compar ed to bulk Si, which we interpret as due to altered electronic structu re in the Si nanostructures. By imposing standing wave boundary condit ions on the valence band wave functions, we calculate the fluorescence spectrum for thin Si sheets of different orientations. For a (100)-or iented sheet, the calculation is in good agreement with the experiment al spectra, suggesting that the nanostructure in porous Si is predomin antly in the form of thin Si (100)-type sheets.