Elti Cattaruzza

Interaction of high‐power laser light with silver nanocluster composite glasses

The size and size distribution of silver nanoclusters embedded in soda‐lime glasses (formed by ion irradiation of Ag+–Na+ ion‐exchanged waveguides) has been modified by high‐power laser irradiation. Optical transmittance in the visible range is found to increase above the energy threshold E*=0.3±0.1 J/cm2 for λ=532 nm and E*=5±1 J/cm2 for λ=1064 nm for pulse lengths of about 10 ns. Cluster size reduction has been observed. Small radii silver nanoclusters are also formed after laser irradiation of ion‐exchanged waveguides. The optical response of the composites has been determined by optical absorption spectroscopy. Transmission electron microscopy, x‐ray photoelectron and Auger electron spectroscopies, and Rutherford backscattering spectrometry have been used to characterize the composites.

Z-scan study on the nonlinear refractive index of copper nanocluster composite silica glass

We used the Z-scan technique for measuring the nonlinear refractive index n2 of a thin composite film formed by copper nanoparticles embedded in silica glass. By varying the number of pulses of the laser shot, we evidenced heating effects induced by the laser during measurements. We were able to estimate the nonthermal refractive-index value, n2=(3.0±0.3)×10−12 cm2/W.

Synthesis of silver clusters in silica-based glasses for optoelectronics applications

Abstract The techniques of silver–sodium ion exchange and Ag + ion implantation in glass have been successfully applied for producing silver clusters in soda-lime glass optical waveguides. Optical absorption spectroscopy, time and spectrally resolved photoluminescence, Rutherford backscattering spectrometry, X-ray photoelectron spectroscopy and transmission electron microscopy measurements were made. Structural changes of the Ag + environment were observed in ion-exchanged samples prepared in liquids with different Ag + concentrations. Heat treatments in air and in H 2 atmospheres induced cluster formation in ion-exchanged samples through different reduction–migration mechanisms, whereas clusters formation in ion-implanted samples is related to the defect concentrations induced by the radiation damage.

LARGE THIRD-ORDER OPTICAL NONLINEARITY OF NANOCLUSTER-DOPED GLASS FORMED BY ION IMPLANTATION OF COPPER AND NICKEL IN SILICA

Composite glasses containing different metal nanoclusters were obtained by implanting copper, nickel, or copper+nickel ions in SiO2 glass. The nonlinear refractive index of the composites was determined by the Z-scan method at a wavelength of 770 nm and with a laser pulse duration of 130 fs. Values of n2 up to 0.68 cm2 gW−1 were measured in the case of the Cu+Ni implanted sample.

Cobalt nanoclusters in silica glass: Nonlinear optical and magnetic properties

Fused silica plates were implanted with Co ions at room temperature at the energy of 50 keV and to the fluence of 4×1016 ions cm−2. The formation of metal nanoclusters was observed by transmission electron microscopy. The cluster size distribution is narrow with a mean-diameter value of about 3 nm. Atomic in-depth distribution was determined by Rutherford backscattering spectrometry, whereas the cobalt chemical state was characterized by electron spectroscopies. Nonlinear refractive index n2 is of the order of 0.2 cm2 G W−1, as determined by the Z-scan technique at a wavelength of 770 nm for 130 fs long pulses at a 76 MHz repetition rate. Zero-field-cooled and field-cooled magnetization curves at the liquid-helium temperature exhibit features of superparamagnetic behavior that are characteristic of assemblies of single-domain nanoparticles.

Au–Cu alloy nanoclusters in silica formed by ion implantation and annealing in reducing or oxidizing atmosphere

The formation of binary alloy clusters in sequentially ion-implanted Au–Cu silica glass has been studied as a function of the annealing atmosphere. Alloy formation has been unambiguously evidenced in the as-implanted samples. The selective influence on Au precipitation of either oxygen or hydrogen annealing atmosphere leads to separation of gold and copper or to Au–Cu alloy cluster formation, respectively.

Fast nonlinear refractive index of pure and alloy metallic nanoclusters in silica glass

Abstract Fast nonlinear refractive index and nonlinear absorption coefficient were measured at 527 nm of wavelength for composites formed by either copper or gold-silver alloy nanoparticles embedded in silica by the Z-scan technique. A single 6 ps long pulse from a Nd:glass laser was used in the Z-scan measurement, allowing to determine the fast (i.e., non-thermal) component of the nonlinear response. Both the composites exhibit relatively large (and negative for the Au–Ag alloy) nonlinear index. Transmission electron microscopy, optical absorption and extended X-ray absorption fine structure spectroscopies were also used to characterize the samples. Some figures of merit for the two samples were evaluated, as well as the third-order optical susceptibilities.

Silver nanocluster formation in ion-exchanged glasses by annealing, ion beam and laser beam irradiation: An EXAFS study

Extended X-ray absorption fine structure analysis is used to determine the silver local environment in silicate glasses doped by the Ag-alkali ion-exchange process, followed by different treatments, namely, ion irradiation, thermal annealing in reducing atmosphere, laser irradiation. The obtained results indicate that metal nanocluster composites with different cluster structures may be formed with these multistep methodologies, pointing out the role of the preparation parameters in giving rise to different features. Lattice parameters and cluster diameter were determined by grazing incidence X-ray diffraction.

Chemical aspects in copper‐implanted fused silica and soda‐lime glasses

Fused silica and soda‐lime glasses were implanted with copper, copper+nitrogen and copper+argon. Samples were characterized primarily by x‐ray photoelectron spectroscopy and x‐ray‐excited Auger electron spectroscopy. Measurements of optical absorption, transmission electron microscopy, secondary‐ion mass spectrometry, and Rutherford backscattering spectrometry were also carried out. Copper nanocluster formation and their size have been found to depend on the reactivity of the host vitreous matrix as well as on the implanted metal concentration. In the copper+nitrogen‐implanted fused silica a chemical interaction between copper and nitrogen together with the dissolution of the metallic nanoclusters has been observed. In the copper+nitrogen‐implanted soda‐lime glass interactions between substrate and nitrogen occur without the dissolution of copper precipitates. The dissolution of copper clusters is induced in the soda‐lime glass when implantation with argon (which does not chemically react with the host gl...

Chemical and physical routes for composite materials synthesis: Ag and Ag2S nanoparticles in silica glass by sol–gel and ion implantation techniques

Two composite systems, “Ag” and “Ag–S” nanoparticles in silica films, were approached by using two different synthesis routes, namely sol–gel and ion implantation. Silica composites containing embedded nanosized silver- and silver sulfide-crystallites were obtained by the sol–gel process. The formation of silver nanograins was also observed in Ag-implanted silica samples, while sequential implantation (first Ag then S) led to the formation of core–shell Ag–Ag2S nanoclusters. The systems were then characterised using different analytical tools, i.e. X-ray photoelectron spectroscopy (XPS), X-ray-excited Auger electron spectroscopy (XE-AES), X-ray diffraction (XRD), secondary-ion mass spectrometry (SIMS), Rutherford backscattering spectrometry (RBS) and transmission electron microscopy (TEM). These advanced microscopic and X-ray analytical methods were combined to gain complementary information concerning the composition and microstructure of the investigated composite systems. In addition, the characterisation of both systems by means of several investigation techniques provided a valuable insight into the potential features offered by sol–gel and ion implantation and enabled a fruitful comparison between these preparative routes. The influence of the different synthesis parameters on the final features of the composites is analysed and discussed.