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Paramagnetic centers at and near the Si/SiOx interface in porous silicon

Formation of paramagnetic centers in aged porous silicon samples is studied by electron paramagnetic resonance. Samples oxidized by aging in air at room temperature exhibit the Pb centers as dominant defects. These are formed at the interfaces between the Si nanocrystallites and the amorphous SiOx layer into which the nanocrystallites are embedded and which is formed during the aging. No other paramagnetic centers, such as the E center that is characteristic of thin SiO2 layers on Si, are observed. This finding is explained by the hydrogen passivation of E centers in oxygen-rich porous structures and by the instability of the E center near the interface. The Pb center is stable after irradiation. © ; ; 1994 American Institute of Physics.

molecular hydrogen ; photoluminiscence ; defects ; Si ; irradiation ; oxides ; rays

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