Photoluminescence and Raman study of iron-passivated porous silicon

Degradation of porous silicon (PS) fabricated by laser-induced etching was studied using photoluminescence (PL) and Raman spectroscopy. Freshly prepared samples were given a heat treatment in hydrofluoric acid plus ferric nitrate solution to produce ironpassivated porous silicon (IPS) samples. PL measurements on IPS show different peak positions and widths as compared to freshly prepared non-passivated PS samples. Results were analyzed using a quantum confinement model. Exposing IPS to air for more than 4 months resulted in no degradation of PL intensity or changes in the peak position and size distribution. Raman spectra of IPS also revealed changes in line-shape asymmetry in comparison to freshly prepared non-passivated PS samples. The data were explained using the phonon confinement in two-dimensions. There is good agreement between PL and Raman data for the size of nanocrystallites participating in iron-passivation. (C) 2002 Elsevier Science B.V. All rights reserved.