Quantum confinement in porous silicon as a function of size distribution of luminescent sites

Photo Luminescence Yield (PLY) and Total Electron Yield (TEY) techniques have been applied simultaneously to porous silicon at the Si K edge to obtain XANES and EXAFS spectra. Experimental results confirm that PLY is able to monitor only the luminescent sites, contrary to TEY, which provides average structural information on all Si sites of the porous layer. The luminescent sites are the smaller and more disordered ones. The peculiar site sensitivity of PLY-XANES spectra obtained at different emission energy from the same X-ray excited optical luminescence band (XEOL) allows us to study the effects of the size distribution of different luminescent sites present in the same sample on the local electronic structure. The paper presents an experimental confirmation of the quantum confinement origin of the photoluminescence in p-Si, obtained for the first time by a site selection inside the same porous silicon sample.