RESONANTLY EXCITED PHOTOLUMINESCENCE FROM POROUS SILICON - EFFECTS OFSURFACE OXIDATION ON RESONANCE LUMINESCENCE SPECTRA

We have studied the photoluminescence mechanism of freshly prepared an d naturally oxidized porous silicon by fluorescence-line-narrowing spe ctroscopy. The surfaces of fresh and oxidized porous silicon are termi nated by silicon hydrides and silicon dioxide. respectively. The TO-ph onon-related structure in resonantly excited luminescence is clearly o bserved in H-terminated porous silicon. After surface oxidation, the l uminescence intensity increases and a structure in the resonant lumine scence appears due to the coupling of excitons and local vibrations at the surface. The effect of surface oxidation on the luminescence spec trum of Si nanocrystals is discussed.