CO2 laser–induced precipitation of semiconductor nanoparticles in a dense glass
Résumé
Nanostructures based on II-VI semiconductor nanocrystallites (NCs) embedded in glass have been studied for many years. Among these systems, the pseudo-binary CdSxSe1-x nanostructures are of particular interest, owing to their optical absorption and emission spectra that cover the entire visible spectral region. Laser irradiation methods have been shown to allow the local growth of several types of NCs in various kinds of matrices. Unfortunately, in the case of the CdSxSe1-x doped silicate glasses, a near-infrared fs laser irradiation, instead of nucleating NCs, leads to permanent refractive index changes in micro-size regions within the glass and may even provoke glass damages at the highest pulse energies. A novel method allowing the local growth of semiconductor nanoparticles in dense silicate glasses is presented. In this method, combining a continuous middle-infrared laser irradiation and a heat-treatment in open air, a transparent melt-quenched borosilicate glass containing CdSxSe1-x nanocrystals was annealed at a temperature below the softening point. Simultaneously, a continuous infrared laser irradiation at 10.6 µm was applied, acting as a thermal addition. Spectroscopic studies reveal the local growth of CdSxSe1-x nanoparticles, with a homogeneous composition and average particle radii ranging from 1.9 to 5.5 nm. These results demonstrate the feasibility of coupling a laser irradiation with an appropriate heat-treatment in order to achieve the spatial organization.