New precursors to form gold nanoparticles in silica monoliths by direct laser-irradiation

PosterInternational audienc

CO2 laser-induced precipitation of CdSxSe1−x nanoparticles in a borosilicate glass: A new approach for the localized growth of quantum dots

International audienceA 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. Resonant Raman, photoluminescence and absorption spectra 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 of nanostructures in vitreous materials

CO2 laser–induced precipitation of semiconductor nanoparticles in a dense glass

International audienceNanostructures 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

Kinetics of gelation and densification of nanoporous silica xerogels: a structural and textural study

International audienc

Building nanoparticles in a matrix with a laser: several examples

OralInternational audienc

Control of gallium incorporation in sol–gel derived CuIn(1−x)GaxS2 thin films for photovoltaic applications

International audienceIn this paper, we report the elaboration of Cu(In,Ga)S2 chalcopyrite thin films via a sol–gel process. To reach this aim, solutions containing copper, indium and gallium complexes were prepared. These solutions were thereafter spin-coated onto the soda lime glass substrates and calcined, leading to metallic oxides thin films. Expected chalcopyrite films were finally obtained by sulfurization of oxides layers using a sulfur atmosphere at 500 °C. The rate of gallium incorporation was studied both at the solutions synthesis step and at the thin films sulfurization process. Elemental and X-ray diffraction (XRD) analyses have shown the efficiency of monoethanolamine used as a complexing agent for the preparation of CuIn(1−x)GaxS2 thin layers. Moreover, the replacement of diethanolamine by monoethanolamine has permitted the substitution of indium by isovalent gallium from x = 0 to x = 0.4 and prevented the precipitation of copper derivatives. XRD analyses of sulfurized thin films CuIn(1−x)GaxS2, clearly indicated that the increasing rate of gallium induced a shift of XRD peaks, revealing an evolution of the lattice parameter in the chalcopyrite structure. These results were confirmed by Raman analyses. Moreover, the optical band gap was also found to be linearly dependent upon the gallium rate incorporated within the thin films: it varies from 1.47 eV for x = 0 to 1.63 eV for x = 0.4

Synthesis and nonlinear optical properties of zirconia-protected gold nanoparticles embedded in sol–gel derived silica glass

International audienceA new approach to dope a silica glass with gold nanoparticles (GNPs) is presented. It consisted in embedding zirconia-coated GNPs in a silica sol to form a doped silica gel. Then, the sol-doped nanoporous silica xerogel is densified leading to the formation of a glass monolith. The spectral position and shape of the surface plasmon resonance (SPR) reported around 520 nm remain compatible with small spherical GNPs in a silica matrix. The saturable absorption behavior of this gold/zirconia-doped silica glass has been evidenced by Z-scan technique. A second-order nonlinear absorption coefficient β of about −13.7 cmGW−1 has been obtained at a wavelength near the SPR of the GNPs

Control of gallium incorporation in sol-gel derived CuIn(1-x)GaxS2 thin films for photovoltaic applications.

International audienc

Synthesis of gold nanoparticles within silica monoliths through irradiation techniques using Au(I) and Au(III) precursors

The formation of gold nanoparticles (GNPs) within mesoporous silica matrices by means of irradiation techniques is reported. The xerogels were impregnated with solutions of two different gold precursors: (Ph3P)AuCl for Au(I) and [nBu4N]AuCl4 for Au(III). The irradiations were performed with two continuous wave laser sources (266 and 532 nm), with a femtosecond pulsed laser (800 nm), and with a mercury vapour lamp emitting in the UV region. It has been shown that no reducing agent was ever required to obtain GNP formation. XRD data exhibited the typical patterns of fcc gold, except for two cases involving the Au(I)-doped matrices, where a preferential crystallographic orientation was observed. Excluding the case of the UV irradiations performed on Au(III)-doped samples, we always obtained the formation of roughly spherical and well dispersed GNPs of relatively small size (6\u201360 nm). The gold-reduction mechanisms proposed depend on the chosen irradiation technique. Moreover, when laser sources are employed, GNP formation can be selectively limited to the irradiated areas, thus making it possible to obtain reproducible patterns of GNPs

Silicon Nanostructures for Photovoltaics

International audienceSiOx/SiO2 and SiOx/SiNx multilayers have been grown by reactive magnetron sputtering. Different fabrication parameters have been studied to optimize the density of Si nanoparticles (Si-nps) within the SiOx sublayer. The aim is to favor the optical properties of the film as well as the carrier transport for the future development of Si-np-based solar device. This chapter evidences the beneficial role of the SiNx sublayer on the achievement of good optical properties in a lower thermal budget with respect to the SiOx/SiO2 counterparts