Renzo Bertoncello

Peculiarities and application perspectives of metal-ion implants in glasses

Abstract Ion implantation in insulators causes modifications in the refractive index as a result of radiation damage, phase separation, or compound formation. As a consequence, light waveguides may be formed with interesting applications in the field of optoelectronics. recently implantation of metals ions (e.g. silver, copper, gold, lead, etc.) showed the possibility of small radii colloidal particles formation in a thin surface layer of the glass substrate. These particles exhibit an electron plasmon resonance which depends on the optical constants of the implanted metal and on the refractive index of the glass host. The non-linear optical properties of such colloids, in particular the enhancement of optical Kerr susceptibility, suggest that the ion implantation technique may play an important role for the production of all-optical switching devices. In this paper an analysis of the state-of-the-art of the research in this field will be presented in the framework of ion implantation in glass physics and chemistry.

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.

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.

Chemical and compositional changes induced by N+ implantation in amorphous SiC films

The effects of 30 keV N+ implantation in amorphous silicon carbide films deposited on silicon substrates by rf sputtering over a fluence range of 1×1016–2×1017 ions cm−2, are studied by means of x‐ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and infrared (IR) absorption techniques. The ion‐induced modifications of these films have been investigated on the basis of the chemical state evolution of Si, C, and N (using XPS and AES) and on the basis of the vibrational features of the films components (using IR absorption). The results show that implanted N bonds Si selectively, substituting the C atoms in the silicon carbide, and the C substitution by N results in a composite layer of carbonitrides and free C. An ion‐induced C transport has also been observed and correlations are established between the formation of silicon carbonitrides and the dynamical behavior of the C in the implanted layer. The latter appears as a superposition of (a) a chemically induced atomic redistribution...

Preparation of anodes for oxygen evolution by electrodeposition of composite oxides of Pb and Ru on Ti

Composite oxides of Pb and Ru have been deposited on Ti rotating disc electrodes and tested as anode materials for the oxygen evolution reaction (oer) from aqueous sulfuric acid. The composite oxides have been anodically deposited according to two different procedures: (i) the electrolysis of suspensions of RuO2 particles in Pb2+-containing electrolytes, or (ii) the electrolysis of solutions containing both Pb2+ and Ru3+. Both procedures are essentially successful, as the passivation of Ti (previously etched in aqueous HF) does not prevent oxide deposition. The former route leads to more active materials than the latter. Considering the oer overpotential and service life, the performance of these layers deposited on Ti is comparable to or better than those of oxides grown on a noble substrate (described in a previous paper).

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...

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...

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.

XPS and UV-VIS study of high-purity Fe2O3 thin films obtained using the sol-gel technique

Fe2O3 thin films obtained by the sol-gel technique from ethanolic solutions of Fe(OEt)3 have been deposited on pure silica and heat treated at two different temperatures. Preliminary thermogravimetric (TG) measurements on the precursor were carried out in order to evaluate the weight loss as a function of temperature and heat-treatment time. Chemical characterization of the films was obtained by XPS and UV–VIS spectroscopies. The bulk of the film heated at 500 °C did not show residual carbon. The corresponding UV–VIS spectrum was well structured in the 15 000–50 000 cm–1 region due to charge-transfer and inner-oxygen transitions. XRD measurements showed an amorphous pattern for the sample heated at 200 °C, whereas a diffraction peak corresponding to haematite (α-Fe2O3) nanocrystals was observed for the film heated at 500 °C.

Chemical Interactions in Titanium- and Tungsten-Implanted Fused Silica

Abstract Silica glasses were implanted with titanium at energies of 30 and 190 keV at a dose of 5 × 1016 cm−2 and with tungsten at 200 keV and dose of 1.6 × 1016 cm−2 and 5 × 1016 cm−2. A set of titanium- and tungsten-implanted samples was also subsequently implanted with nitrogen in the energy range of 15–100 keV and dose of 2 × 1017 cm−2. Samples were characterized by X-ray photoelectron spectroscopy, secondary ion mass spectrometry, Rutherford backscattering spectrometry, nuclear reaction analysis and, partially, IR-diffuse reflectance. Titanium silicide and titanium oxide compounds were observed in titanium-implanted samples. Subsequent nitrogen implantation destroys the titanium silicide species, inducing the formation of titanium metallic clusters and substoichiometric silicon nitrides: titanium oxides are transformed to titanium oxynitrides. Tungsten implantation causes the formation of metallic tungsten precipitates and the presence of tungsten oxides was observed. Nitrogen implantation favours the formation of tungsten oxynitrides. Thermodynamic considerations were applied to explain the chemical interactions between implanted species and substrate.