In order to identify luminescent centers in aged porous material, time-resolved vibration spectra in the 750 to 2000/cm region and in the visible luminescence spectra were studied. Laser excitation gave rise to emission characteristics of porous material, as well as a strong bleaching of the infra-red spectrum in the region of the ground-state Si-O stretching vibration frequencies at 1100 and 1235/cm. New transient absorption bands appeared in this region as a result of laser excitation. Three characteristic lifetimes in the decay of the bleach band at 1235/cm were observed. These were similar to the observed decay times of the photoluminescence from porous material. The results suggested that the emitting centers in aged porous material were trapped excitation sites in an inhomogeneously defective oxidized surface.

Time-resolved Fourier-transform infrared and visible luminescence spectroscopy of photoexcited porous silicon J.Wang, L.Song, B.Zou, M.A.El-Sayed: Physical Review B, 1999, 59[7], 5026-31