Energy transfer channel between silicon nanocrystals and an optical center emitting above their bandgap

Abstract

This paper reports on the observation of an electronic energy transfer channel between silicon nanocrystals and the SiO2 matrix they are embedded in. This energy transfer manifests itself by photoluminescence at 650 nm, i.e. above the indirect band gap, in superlattices formed by alternating layers of P- or B-doped as well as undoped silicon nanocrystals (NCs) and stoichiometric SiO2 or SiOxNy. This band is only observable under strong (above ~13 mJ/cm2) UV femtosecond excitation. A detailed investigation of the excitation intensity dependence together with luminescence dynamics enabled us to ascribe this band to a non-bridging oxygen hole center located in the SiO2 (or SiOxNy) matrix, to study the influence of NC treatment on its photoluminescence and to determine the energy transfer mechanism.