Unité Matériaux Avancés et Optronique, Faculté des Sciences de Tunis, 1008 Campus Universitaire Tunis, Tunisia
INSP, UPCM University Paris 06, CNRS UMR 7588, Campus Boucicaut, 140 rue de Lourmel, 75015 Paris, France
Faculté des Sciences de Bizerte, 7021 Zarzouna, Bizerte, Tunisia
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 m and 14 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.
(Received April 25 2008)
(Revised July 14 2008)
(Accepted October 13 2008)
(Online publication January 14 2009)