Strong- and nondegrading-luminescent porous silicon prepared by hydrothermal etching

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Abstract
Porous silicon (PS) with strong and nondegrading photoluminescence (PL) is prepared by iron-passivating hydrothermal etching. The PL peak intensity of freshly as-prepared PS is as ∼2 times strong as that of conventionally anodized PS. This peak intensity reaches a saturation after the samples are annealed at 120 °C for ∼3 h, which is ∼2.5 times strong as that of freshly prepared samples. Exposing the annealed samples to air for ten months, no degradation of the PL intensity occurs and the peak energy remains constant all through the period. Microstructural studies disclose that the participation of iron ions in the hydrothermal process is crucial to the generation of the high-density silicon nanocrystallites and the construction of the solid surface passivation. These two structural properties are responsible for the strong and nondegrading PL of as-prepared PS.