Resonantly excited photoluminescence from porous silicon: Effects of surface oxidation on resonance luminescence spectra

We have studied the photoluminescence mechanism of freshly prepared and naturally oxidized porous silicon by fluorescence-line-narrowing spectroscopy. The surfaces of fresh and oxidized porous silicon are terminated by silicon hydrides and silicon dioxide. respectively. The TO-phonon-related structure in resonantly excited luminescence is clearly observed in H-terminated porous silicon. After surface oxidation, the luminescence intensity increases and a structure in the resonant luminescence appears due to the coupling of excitons and local vibrations at the surface. The effect of surface oxidation on the luminescence spectrum of Si nanocrystals is discussed.