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

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 similar to 2 times strong as that of conventi onally anodized PS. This peak intensity reaches a saturation after the samp les are annealed at 120 degrees C for similar to 3 h, which is similar to 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 an d the peak energy remains constant all through the period. Microstructural studies disclose that the participation of iron ions in the hydrothermal pr ocess is crucial to the generation of the high-density silicon nanocrystall ites and the construction of the solid surface passivation. These two struc tural properties are responsible for the strong and nondegrading PL of as-p repared PS. (C) 1999 American Institute of Physics. [S0003-6951(99)00903- 1 ].