[en] In this work, we investigate the structural properties and, in particular, the residual stress of carbon-implanted TiN coatings by means of glancing incidence X-ray diffraction and secondary ion mass spectrometry techniques. The coatings were grown by ion-beam physical vapor deposition on steel substrates and subsequently implanted at 100 keV with carbon doses of 1x10¹⁷,3x10¹⁷ and 7x10¹⁷ ions/cm². The carbon depth profiles obtained by secondary ion mass spectrometry enable us to choose the more appropriate X-ray beam incidence angles in order to detect the structural variations in proximity to the implanted region. The X-ray results indicate notable variations both in the crystallinity and in the residual stress and such modifications depend on the carbon dose and penetration depth. In particular, in the coating implanted with a dose of 1x10¹⁷ ions/cm² the initial compressive residual stress is reduced until a penetration depth of at least 400 nm. In addition, the lattice is re-crystallized in the first 100 nm. The coatings implanted with doses of 3x10¹⁷ and 7x10¹⁷ ions/cm² have a surface region (100 nm thick) in the tensile stress state and a peak of compressive stress well above the non-implanted value at a depth between R_p and 2R_p. Moreover, the effect of C⁺ implantation is to reduce the lattice parameters for all the investigated samples. Such results can be explained by considering the defect distribution induced by the implantation process and the competition between the implantation amorphization and the self-annealing behavior

[en] The nanostructural and magnetic properties of Fe-Al/SiO₂ granular solids prepared by ion implantation have been investigated. A strong effect of the implantation order of the Fe and Al ions has been evidenced. By implanting first the Al ions and later Fe ions, 5-40 nm core-shell nanoparticles are formed with a magnetic behavior similar to that of Fe. The lattice parameter of the nanoparticles is consistent with that of the α-Fe. By changing the implantation order, 10-15 nm core-shell nanoparticles of a bcc Fe-based phase with a lattice 2.5% smaller than that of α-Fe are formed. The temperature dependence of the magnetization indicates a superparamagnetic behavior

[en] Nanocrystals of wide band gap materials (GaN and In₂O₃) were synthesized by sequential ion implantation in dielectric substrates, followed by thermal annealing of the samples. Transmission electron microscopy, extended X-ray absorption fine structure spectroscopy and grazing incidence X-ray diffraction analyses confirmed the formation of GaN and In₂O₃ crystalline nanoparticles. Blue shift of the near-edge photoluminescence (PL) band (quantum confinement effect) was observed for GaN nanocrystals. A strong PL band peaked at 3.35 eV was detected upon excitation of In₂O₃ nanocrystals at 5.20 eV

[en] We present an experimental and theoretical study on the structural properties of ZnO nanoparticles embedded in silica. The ZnO-SiO₂ nanocomposite was prepared by ion implanting a Zn⁺ beam in a silica slide and by annealing in oxidizing atmosphere at 800 deg. C. From an experimental point of view, the structural properties of the ZnO-SiO₂ nanocomposite were studied by using glancing incidence X-ray diffraction. According to the results, zinc crystalline nanoclusters with an average diameter of 13 nm are in the as-implanted sample. The annealing in oxidizing atmosphere promotes the total oxidation of the Zn nanoclusters and increases their size until to an average of 22 nm. Moreover, the formed ZnO nanocrystals have a preferential (0 0 2) crystallographic orientation. From a theoretical point of view, the preferential orientation of the ZnO nanoparticles can be explained satisfactory by the minimization of the strain energy of the nanoparticles placed in proximity of the surface of the matrix

[en] Fused silica substrates were implanted with 2x10¹⁷ In²⁺/cm² ions at 320 keV. Indium crystalline nanoclusters with an average size of about 15-20 nm were found in the as-implanted samples. The thermal behavior of the nanoclusters was studied by performing heating-cooling cycles in vacuum and by using in-situ techniques based on glancing-incidence x-ray diffraction and transmission electron microscopy. The precipitates showed both superheating and supercooling. Moreover, no evidence of clusters growth or reorientation during the thermal cycle was found. A detailed study of the heating sequence showed that the melting temperature of the Indium precipitates depended on their size, i.e., the smallest particles melt first and at a temperature which is about 7 K below the bulk melting point, while the largest ones were superheated until about 13 K above it. Moreover, a remarkable stability of the In cluster well above their melting temperature (up to about 980 K) was evidenced by in-situ transmission electron microscopy analysis. From a thermodynamic point of view, the experimental results were explained by considering two effects acting on the clusters: the thermodynamic size effect and the pressure of the silica matrix

[en] Thin ZrN _xO _y films are deposited on Si (100) substrates by radio frequency (RF) reactive magnetron sputtering of a zirconium target in an argon-oxygen-nitrogen mixture. The Φ _N2/Φ _(Ar+N2+O2) ratio was varied in the range 2.5%-100% while the oxygen flux was kept constant. The films were characterized by combining several techniques: X-ray photoelectron spectroscopy, X-ray diffraction and Secondary Ion Mass Spectroscopy. The relationship between structural and compositional properties and the sputtering parameters was investigated. Increasing nitrogen partial pressure in the gas mixture, a chemical and structural evolution happens. At lowest nitrogen flux, ZrN cubic phase is formed with a very small amount of amorphous zirconium oxynitride. At highest nitrogen flux, only crystalline ZrON phases were found. For the films obtained between these two extremes, a co-presence of ZrN and ZrON can be detected. In particular, chemical analysis revealed the co-presence of ZrO₂, ZrN, ZrON and N-rich zirconium nitride which is correlated with the Φ _N2/Φ _(Ar+N2+O2) values. A zirconium nitride crystal structure with metal vacancies model has been considered in order to explain the different chemical environment detected by X-ray photoelectron spectroscopy measurements. The metal vacancies are a consequence of the deposition rate decreasing due to the target poisoning. It's evident that the growth process is strongly influenced by the zirconium atoms flux. This parameter can explain the structural evolution

[en] Tin dioxide nanoparticles embedded in silica matrix were fabricated by ion implantation combined with thermal oxidation. Silica substrate was implanted with a 150 keV Sn⁺ ions beam with a fluence of 1.0 x 10¹⁷ ions/cm². The sample was annealed for 1 h in a conventional furnace at a temperature of 800 ^oC under flowing O₂ gas. According to the structural characterization performed by X-ray diffraction and transmission electron microscopy techniques, metallic tetragonal tin nanoparticles with a volume average size of 12.8 nm were formed in the as-implanted sample. The annealing in oxidizing atmosphere promotes the total oxidation of the tin nanoparticles into tin dioxide nanoparticles with a preferential migration toward the surface of the matrix, where large and coalesced nanoparticles were observed, and a small diffusion toward the bulk, where smaller nanoparticles were found.

[en] We have developed highly sensitive microacoustic vapor sensors based on surface acoustic waves (SAWs) configured as oscillators using a two-port resonator 315, 433 and 915 MHz device. A nanocomposite film of single-walled carbon nanotubes (SWCNTs) embedded in a cadmium arachidate (CdA) amphiphilic organic matrix was prepared by Langmuir-Blodgett technique with a different SWCNTs weight filler content onto SAW transducers as nanosensing interface for vapor detection, at room temperature. The structural properties and surface morphology of the nanocomposite have been examined by X-ray diffraction, transmission and scanning electron microscopy, respectively. The sensing properties of SWCNTs nanocomposite LB films consisting of tangled nanotubules have been also investigated by using Quartz Crystal Microbalance 10 MHz AT-cut quartz resonators. The measured acoustic sensing characteristics indicate that the room-temperature SAW sensitivity to polar and nonpolar tested organic molecules (ethanol, ethylacetate, toluene) of the SWCNTs-in-CdA nanocomposite increases with the filler content of SWCNTs incorporated in the nanocomposite; also the SWCNTs-in-CdA nanocomposite vapor sensitivity results significantly enhanced with respect to traditional organic molecular cavities materials with a linearity in the frequency change response for a given nanocomposite weight composition and a very low sub-ppm limit of detection

[en] The nanostructural and magnetic properties of FeAl-SiO₂ granular solids prepared by sequential ion implantation have been investigated as a function of the annealing atmosphere (either oxidizing or reducing) and implantation order. Nanoscopic particles with a bcc structure were found in both as-implanted samples. In the sample Al-Fe prepared by implanting first the Al ions and later the Fe ions, the lattice parameter indicates the presence of practically pure iron nanoparticles. On the other hand, in sample Fe-Al with the implantation order inverted, the lattice parameter is consistent with the presence of an iron rich iron-silicon alloy. The magnetic data confirm the presence of the pure Fe and the Fe-Si alloy in the as-implanted samples and the absence of FeAl intermetallic compounds. The annealing in Ar/H₂ promotes the growth of the clusters and increases the Si content in the particles in both samples. In Fe-Al sample, this induces a disorder-order phase transition from the disordered Fe-Si solid solution to the Fe₃Si phase and the coprecipitation of the ordered FeSi phase. The magnetic moment increases after the annealing in Ar/H₂ due to the incorporation of the iron atoms dispersed in the matrix and to the higher crystalline order. The annealing in air is responsible essentially of the growth of the Fe-Si clusters in both samples. On the other hand, in sample Al-Fe the oxygen interacts with the pure iron clusters by promoting the Fe₂O₃ formation