Photoluminescence properties of porous silicon nanocomposites

Different porous silicon (PS) layers were impregnated with rhodamine 6G (Rh) solution in order to form Rh/PS nanocomposites. The effect of the porous matrix (fresh, oxidised, type p+) on the propriety of photoluminescence (PL) has been investigated. It was found that the luminescence of this nanocomposite is provided by an energy transfer from PS nanocristallites to rhodamine and from interaction of dye molecules with the chemical species on the Si surface. An antistokes PL has been observed using a He–Ne laser excitation. The dependence of its intensity via power excitation suggests a process of two-step two-photon absorption as origin of this PL. Nanocomposite formed by PS and ZnO has been also investigated. We show that this transparent oxide does not degrade the skeleton of PS and does not inhibit PL. The PL band shifts to high energy and the intensity becomes stable providing the passivation of the dangling bonds on the Si-surface by ZnO.