Photoluminescence increment of Si nanocrystals in presence of Ag nanoparticles

Plasmonics is the most promising field appointed to continue the predictions of the Law of Moore as well as for the confinement of light on a subwavelength spatial scale, allowing the breaking of the diffraction limit. In that direction, we have produced by ion implantation, interesting nanocomposites with very attractive optical properties. Recently, a double implantation of Si and Ag ions in silica, with subsequent thermal treatments in appropriated atmospheres, allowed us to obtain two layers: one of Si nanocristals (NCs), and other of Ag nanoparticles (NPs). This arrangement shows an enhancement of the emission of Si nanocrystals (NCs) in a new, totally integrated configuration. The synthesis of the system by ion implantation offers a total protection of the optical active agents from environmental effects such as oxidation, additionally assuring a high degree of homogeneity. We present a photoluminescence excitation study (420-500 nm) of Si NCs, with and without the presence of Ag nanoparticles (NPs), both embedded in a matrix of SiO2. The level of saturation for Si NCs is independent of the excitation wavelength, but for Si NCs in the presence of Ag NPs, a saturation level arises for excitation wavelengths near the absorption band of the surface plasmon resonance of the Ag NP (325-475 nm). The increase of both, the values of saturation and excitation cross-section of Si NCs in the presence of Ag NPs, is an evidence of the optical interaction between the metal NPs and Si NCs studied in this work. This suggests a decrease of the lifetime of Si NCs photoemission due to the interaction with the Ag NPs.