Spectroscopic ellipsometry in the mid infrared spectral range, Raman
scattering and TEM measurements on (100) oriented p+ and n+-type
porous silicon (PS) samples were carried out. Porosities of 68% and
48% for p+ and n+ wafers, respectively, and thicknesses of 27.6
$\mu $m and 14 $\mu $m with the same extinction coefficient k = 0.1 were
determined from spectroscopic ellipsometry. Raman scattering measurements
show that the resultant surface morphology of the PS layers consists of
irregular and randomly distributed nanocrystalline Si structures. Using the
phonon confinement model, the diameters of Si nanocrystallites have been
estimated as 8 and 3 nm for p+ PS type and 12 and 5 nm for n+ PS
type. Transmission electron microscopy shows clearly defined pores with
sizes ranging from 15 to 35 nm, inhomogeneously distributed along the PS
surface. We demonstrate that the filling of the PS pores by organic material
(Rhodamine 6G) brings about important enhancement on photoluminescence
intensity.