F. Caccavale

Formation of copper and silver nanometer dimension clusters in silica by the sol‐gel process

Ag and Cu (pure and/or mixture) nanoclusters doped silica films were prepared by the sol‐gel process. In the case of Ag and Cu codoped silica films, Cu/Ag molar ratio was 1, 2, and 3 at constant (Ag+Cu)/SiO2 molar ratio of 0.175. Separated Ag and Cu nanoclusters are formed in the silica matrix. The size of the clusters and their distribution are dependent on the film composition. Optical absorption was measured from 185 to 800 nm. Intensity‐dependent nonlinear refractive index was measured for pure Cu and Ag–Cu (1:1 molar ratio) samples using z‐scan technique in the wavelength range from 570 to 596 nm. The measured nonlinear refractive index is of the order of 10−13 m2/W at a pulse repetition rate of 15.2 MHz.

REVERSE PROTON EXCHANGE FOR BURIED WAVEGUIDES IN LINBO3

The reverse proton-exchange (RPE) process performed in different HxLi1-xNbO3 crystalline phases of proton-exchanged and annealed proton-exchanged LiNbO3 waveguides leads to remarkable optical and compositional modifications. Analysis of ordinary and extraordinary index profiles, correlated with concentration depth profiles in RPE samples subjected to different exchange and postexchange treatments, shows how buried-index optical waveguides in LiNbO3 with symmetric mode and reduced fiber–waveguide coupling losses can be realized.

Experimental study of copper-alkali ion-exchange in glass

Copper–alkali ion exchange was performed by immersing different silicate glasses (soda-lime and BK7) in different molten eutectic salt baths (CuSO4:Na2SO4 and CuSO4:K2SO4). The obtained optical waveguides were characterized by m-lines spectroscopy for the determination of refractive index profiles, and by secondary ion mass spectrometry for the concentration profiles of the ion species involved in the exchange process. The different oxidation states of copper inside the glass structure were studied by electron paramagnetic resonance and x-ray absorption techniques. Interdiffusion copper coefficients were also determined. The Cu–alkali exchange was observed to give rise to local structural rearrangement of the atoms in the glass matrix. The Cu+ ion was found to mainly govern the exchange process, while competition between Cu–Na and K–Na exchanges occurred when a potassium sulfate bath was used. In this case, significant waveguide modal birefringence was observed.

On the formation of silicon oxynitride by ion implantation in fused silica

Abstract The formation of silicon oxynitrides and nitrogen gaseous compounds as a consequence of implantation of nitrogen ions in silica glasses was investigated by XPS analysis. The presence of gaseous compounds is supported by the analysis of the effect of a double implantation: a nitrogen implantation followed by an argon irradiation. Moreover SEM analysis shows, for doses higher than 6 × 1017 N cm−2, a surface morphology characterized by blisters, which can be also ascribed to NO or N2 molecules. These structures are absent in the case of neon implantations. The distribution of nitrogen as a function of the implantation dose was measured by SIMS. With a dose >5 × 1016 cm−2, the nitrogen distribution showed a flat profile limiting the maximum attainable nitrogen concentration and, consequently, the stoichiometry of the SiOxNy compounds. An increase of the nitrogen concentration was obtained for nitrogen implantations in 29Si-preimplanted silica glasses. The nitrogen profile followed the distribution of the preimplanted silicon.

Irradiation-induced Ag-colloid formation in ion-exchanged soda-lime glass

Abstract Ion-exchanged glass samples were obtained by immersing soda-lime slides in molten salt baths of molar concentration in the range 1–20% AgNO3 in NaNO3, at temperatures varying from 320 to 350°C, and processing times of the order of a few minutes. Irradiations of exchanged samples were subsequently performed by using H+m, He+, N+ ions at different energies in order to obtain comparable projected ranges. The fluence was varied between 5 × 1015 and 2 × 1017 ions/cm2. Most of the samples were treated at current densities lower than 2 μA/cm2, in order to avoid heating effects. Some samples were irradiated with 4 keV electrons, corresponding to a range of 250 nm. The formation of nanoclusters of radii in the range 1–10 nm has been observed after irradiation, depending on the treatment conditions. The precipitation process is governed by the electronic energy deposition of incident particles. The most desirable results are obtained for helium implants. The process was characterized by the use of Secondary Ion Mass Spectrometry (SIMS) and nuclear techniques (Rutherford Backscattering (RBS), Nuclear Reactions (NRA)), in order to determine concentration-depth profiles and by optical absorption and Transmission Electron Microscopy (TEM) measurements for the silver nanoclusters detection and size evaluation.

Secondary‐ion‐mass spectrometry and near‐field studies of Ti:LiNbO3 optical waveguides

Secondary‐ion‐mass spectrometry (SIMS) and near‐field (NF) methods have been applied to study Ti:LiNbO3 optical waveguides. Ti concentration as a function of diffusion process parameters has been studied by the SIMS method. The main determining factors that were found to affect the depth‐diffusion behavior of titanium in LiNbO3 slab waveguides are the initial thickness of the dopant film and the diffusion temperature. Anisotropy in the diffusion rate for Xand has been applied to the refractive index profile reconstruction for single‐mode optical channel waveguides. A sharp change in the index at the air–guide interface has been observed, as expected. The dependence of refractive index change on Ti concentration has been found to be nonlinear, such as quadratic, approximately.

N AND AR ION-IMPLANTATION EFFECTS IN SIO2-FILMS ON SI SINGLE- CRYSTAL SUBSTRATES

The chemistry of an argon‐ion‐irradiated interface between an amorphous silicon dioxide film and a silicon single‐crystal substrate was studied by determining the kind and depth distribution of compounds formed after nitrogen implantation at a depth more shallow than the SiO2 film thickness. With this study we intended to obtain some insight into the chemical and physical processes involved in the formation of silicon oxynitrides in silica as a consequence of nitrogen ion implantations. Samples were mainly characterized by x‐ray photoelectron and Fourier‐transform infrared spectroscopies. Scanning electron microscopy, Rutherford backscattering spectrometry, nuclear reaction analysis, and secondary‐ion mass spectrometry techniques were also used to complete the set of results. The experimental evidences are consistent with a picture of an argon‐induced radiation damage in terms of Si—O and Si—Si bond breaking in the SiO2 and in the silicon substrate regions, respectively. The subsequently implanted nitroge...

Characterisation of antireflective TiO2//SiO2 coatings by complementary techniques

Abstract Reactive magnetron sputtering deposition processes based on rotating or double cathodes allow the deposition of multiple TiO2//SiO2 layers on glass for obtaining antireflective coatings for large area applications with a good homogeneity and high resistance against environmental attacks. By increasing the number of TiO2//SiO2 layers, the luminous reflectance of the coated glass decreases but the calculation of angular daylight and energy parameters requires the use of an increasing number of complementary analytical techniques due to the complexity of the coating. In this paper we show how Rutherford back-scattering, neutron reflectivity and spectrophotometry can be successfully utilised to perform a quite complete characterisation of commercial antireflective coatings based on three TiO2//SiO2 layers.

High fluence implantation in glasses: chemical interactions

Abstract Results will be given on chemical interactions in amorphous SiO 2 implanted with reactive and non-reactive species. Samples were implanted with nitrogen, silicon, titanium and silver; a set of samples already implanted with these elements (excluding those implanted with nitrogen) has been subjected to a second implant with nitrogen ions. at the dose of 2 × 10 17 ions cm −2 , at different energies. Samples have been characterized by secondary ion mass spectrometry, X-ray photoelectron spectroscopy, nuclear techniques and optical absorption measurements. Radiation damage and chemical effects have been discriminated; precipitation of the implanted species, as well as chemical compound formation in the interaction both between the implanted species and the host matrix and between the implanted species themselves have been detected.

EPR of some oxide glasses implanted with Mn+ and Cu+ ions

Abstract Electron paramagnetic resonance (EPR) spectra of Mn2+ and Cu2+ ions in some Mn+- and Cu+-implanted multicomponent silicate (20Na2O10B2O370SiO2, mol%) and phosphate (36P2O544Na2O20Al2O3 and 65P2O510B2O310Al2O315MgO, mol%) glasses are presented. About 10% of the implanted copper is present as Cu2+ ions surrounded by six ligands which form a tetragonally elongated octahedron. The concentration of Mn2+ ions in the implanted layers of some glasses is comparable with that of implanted manganese ions. The EPR spectra of Mn+-implanted high-phosphate glass indicate that Mn2+ ions can exist in the implantation layers in local environments similar to those present in bulk glasses with appropriate composition. In addition, Mn2+ ions are present in the implantation layers as paramagnetic ions coupled by spin-spin interactions or antiferromagnetic MnO crystals.