Luminescence from porous silicon:: an optical X-ray absorption fine structures study at the Si L3,2-edge

We report optical luminescence from porous silicon (PS) using excitation photons with energies above and below the Si L-3,L-2-edge. The yield of the luminescence was in turn used to obtain the X-ray absorption fine structures (XAFS) of PS at these edges. It is shown that the small chemically capped nm nodules and pillars as well as encapsulated Si crystallites attached to the "bulk" of the PS network are primarily responsible for the luminescence, not the entire network. It is also noted that the combined use of the total electron yield, the photo luminescence yield and the fluorescence yield in measuring the Si L-3,L-2-edge absorption greatly enhances the capability of the XAFS in site and sampling depth selectivity. K-edge data were also shown for comparison. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.