Raman analysis of light-emitting porous silicon

Porous silicon that strongly emits in the visible was analyzed using Raman scattering. The spectrum peaks near 508 cm−1, has a width of ∼40 cm−1, and is very asymmetric. Using a model of phonon confinement, this suggests that the local structure of porous silicon is more like a sphere than a rod and has a characteristic diameter of 2.5–3.0 nm. Polarization Raman measurements suggest that the structure does not consist of a series of parallel columns.