PHOTOLUMINESCENCE MECHANISM IN SURFACE-OXIDIZED SILICON NANOCRYSTALS

We have studied photoluminescence (PL) properties of surface-oxidized Si nanocrystals fabricated with a SiH4 plasma cell. The size dependenc e of the PL spectrum, the PL decay dynamics, and site-selective excita tion spectroscopy show that the efficient and broad PL band around sim ilar to 1.65 eV originates from excitons localized at the interface be tween crystalline Si and the SiO2 surface layer. The PL from the cryst alline Si core state in large nanocrystals appears in the infrared spe ctral region. By comparison between surface-oxidized Si nanocrystals a nd as-prepared porous Si, the size and surface dependence of the coupl ing between electronic and vibrational excitations are discussed.