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In this paper we report about the synthesis and characterization of graphene oxide (GO). We monitor the effects of the different synthetic processes on the morphological and structural properties of the materials. A modified Hummers' method is adopted to obtain GO powder; H2SO4 is employed as intercalating agent, to increase the distance between graphitic layers, while KMnO4 is used as oxidizing reagent for introducing the oxygen functionalities in the graphitic structure. The oxidized graphite powder is treated in acid solution; different washing cycles are applied. The recovered powders are dispersed in aqueous solution and sonicated for 30 min or 60 min, respectively. Subsequently, these solutions are deposited on Si and SiO2(317 nm)/Si substrates by means of dip coating. GO powders, GO solutions and GO on substrate are characterized through several analytical and spectroscopic techniques. These analyses reveal that the sonication time and the washing procedure of the samples can influence the structure and the morphology of the graphene oxide flakes. Moreover, when KOH is employed as alkaline agent in a chemical reducing treatment of the GO powder before sonication, a considerable alteration of the native structure of graphene oxide is observed. The detailed characterization indicates that the properties of the GO samples are strongly influenced by the chemical and physical treatments to which it is subjected.

Highly porous nanocrystalline TiO2 films were sensitized with ZnS semiconductor nanocrystals by using a three-step facile strategy. The TiO2 matrices were firstly impregnated with the zinc bis(benzyl)thiol precursor that, unlike many other metal chalcogenides, is easily dispersible in the most common organic solvents. In the second step of the adopted synthetic strategy, the TiO2 impregnated with zinc thiolate was annealed at 250 °C in order to induce nucleation and growth of ZnS nanocrystals inside the porous matrices as well as on the film surface. A final cleavage in dichloromethane allowed us to remove all residual organic reagents and products. The size of the ZnS nanocrystals can be tuned by variation of the annealing time as shown by X-ray diffraction measurements, without changing the crystallographic phase structure (zincblende structure). Scanning electron microscopy analysis showed a random spatial dispersion of the ZnS nanocrystals and no remarkable aggregation was observed. The sensor device based on TiO2-ZnS nanocomposite was able to detect NO2 gas at 270 °C down to 1 ppm with negligible response towards reducing gases (CO, CH4). Compared to bare TiO2 film, the TiO2-ZnS nanocomposite shows higher sensitivity and lower recovery time towards an oxidant NO2 gas.

We investigate the short and long term wettability of laser textured stainless steel samples in order to better understand the interplay between surface topography and chemistry. Very different 1D and 2D periodic as well as non-periodic surface patterns were produced by exploiting the extreme flexibility of a setup consisting of five rotating birefringent crystals, which allows generating bursts of up to 32 femtosecond laser pulses with fixed intra-burst delay of 1.5 ps. The change of the surface morphology as a function of the pulse splitting, the burst polarization state and the fluence was systematically studied. The surface topography was characterized by SEM and AFM microscopy. The laser textured samples exhibited, initially, superhydrophilic behaviour which, during exposure to ambient air, turned into superhydrophobic with an exponential growth of the static contact angle. The dynamic contact angle measurements revealed a water adhesive character which was explained by XPS analyses of the surfaces that showed an increase of hydrocarbons and more oxidized metal species with the aging. The characteristic water adhesiveness and superhydrophobicity of laser textured surfaces can be exploited for no loss droplet reversible transportation or harvesting.

In this work, we report on the fabrication of laser induced periodic surface structures (LIPSS) on stainless steel, using bursts of 200 fs sub-pulses at a wavelength of 1030 nm. A cascade of birefringent crystals was used to generate the bursts with tunable number of sub-pulses and intra-burst delays varying between 1.5 ps and 24 ps. Being such a delay shorter than the typical electron-lattice relaxation time in metals, the sub-pulses impinge on the sample surface when the material is still in a transient state after excitation from the first sub-pulse, thus allowing peculiar structures to be generated depending on the burst features. We obtained 1-D and 2-D periodic surface structures and investigated the influence of number of sub-pulses and polarization on their morphology. In particular, when bursts composed by all-aligned linearly polarized sub-pulses were used, 1-D LIPSS were obtained with different periodicity and depths depending on the number of sub-pulses. Bursts with crossed linear polarization or circular polarization sub-pulses produced 2-D LIPSS with morphology varying from triangular structures arranged in hexagonal lattice to pillar-like ordered or disordered structures depending on the bursts features. In most cases these structures exhibit a superhydrophobic behavior, as assessed by static contact angle measurements, which is achieved after a time of exposition to laboratory air. By XPS analysis we investigated the chemical variations occurring on the surfaces over this time.

Zirconium nitride (ZrN) coatings, due to their inherent high hardness, wear and corrosion resistance, as well as the golden color, can be attractive for a wide range of applications, such as mechanical, optical, decorative and biomedical devices. Reactive Bipolar Pulsed Dual Magnetron Sputtering (BPDMS) operating in mid-frequency range is a powerful technique for the deposition of dense coatings, free from morphological defects, at high deposition rate. In fact, the employ of mid-frequency voltage reversals allows suppressing arcs and, as a consequence, stabilizing the reactive sputtering process. Despite the success of the dual bipolar process, there are many aspects of this complex process that are not yet well understood, such as the influence of the target voltage waveforms and plasma parameters on the film growth. In order to fill this lack of knowledge, ZrN films were deposited by BPDMS with different voltage waveforms on the Zr targets and the influence of these deposition parameters on the films’ stoichiometry as well as on their structural and mechanical properties is investigated in this paper. In particular, it was found that, for duty cycle values below 33%, the hardness of the coating increases up to 31 GPa. The analysis of the chemical composition, performed by XPS, detects an almost constant value of stoichiometry along the depth-profile of each film and the N:Zr ratio increases from 1.06 to 1.20 as the duty cycle decreases. Therefore, when the N:Zr ratio is 1.06 we got a stoichiometric ZrN compound, while for N:Zr equal to 1.20 we obtained a lack of Zr atoms with respect to N atoms. Raman spectroscopy confirms the results of XPS analyzes, since it showed some features related to the structural disorder in the sample grown with the lowest duty cycle. © 2017 Elsevier B.V.

The interest about zirconium oxynitrides is growing with the attention for zirconium nitrides phase at high zirconium content. In recent years a great progress has been made to realize both the higher nitride phase (Zr3N4) and the higher oxynitride phase (Zr2ON2) in more ordered crystal structures. In this work the abovementioned two phases are realized by RF magnetron sputtering technique. The characterization results, illustrated in the present paper, push towards the evidence of an evolution from zirconium N-rich nitride to the oxynitride films by introducing a very small percentage (0.5%) of water vapor in a sputtering atmosphere made only of nitrogen gas. In particular, structural analysis identified zirconium N-rich nitride as c-Zr3N4 and zirconium oxynitride as c-Zr2ON2. The formation of zirconium oxynitride is due to oxygen presence, coming from the water dissociation in the plasma. Both phases request an additional energy supplied by substrate bias assistance for c-Zr3N4 and by more energetic particles reflected by the Zr target for c-Zr2ON2.

Thin films of zirconium oxynitride (ZrNO) and titanium oxynitride (TiNO) have been deposited onto Si(100) substrates at room temperature by radiofrequency magnetron sputtering in an argon–oxygen–nitrogen atmosphere. Single oxynitride layers have been stacked to obtain a multilayer structure. The film structure has been determined by X-ray diffraction while compositional analysis has been performed by X-photoelectrons spectroscopy. Structural analysis has shown that TiNO can be represented as a cubic structure where oxygen atoms replace nitrogen ones while ZrNO can be described as a cubic ZrO2 where nitrogen atoms replace oxygen ones. Besides the main peak, the multilayer films show satellite peaks, proving the formation of the stacked structure. The final films stoichiometry has been explained by a growth model. It establishes that in TiNO films the nitrogen vacancies filling by reactive reactions with oxygen atoms is favourite while for ZrNO films the oxygen vacancies filling by energetic nitrogen atoms is more likely to happen. The different behaviour between TiNO and ZrNO is further confirmed during the multilayer growth.

Titanium dioxide nanopowders doped with different amounts of Fe ions were prepared by coprecipitation method. Obtained materials were characterized by structural (XRD), morphological (TEM and SEM), optical (UV/vis reflection and photoluminescence, and Raman), and analytical techniques (XPS and ICP-OES). XRD analysis revealed rutile crystalline phase for doped and undoped titanium dioxide obtained in the same manner. Diameter of the particles was 5–7 nm. The presence of iron ions was confirmed by XPS and ICP-OES. Doping process moved absorption threshold of TiO2into visible spectrum range. Photocatalytic activity was also checked. Doped nanopowders showed normal and up-converted photoluminescence.

We report on the synthesis and characterization of a hyperbranched polymer englobing single-wall carbon nanotubes (SWCNTs). This new material was obtained by using SWCNTs functionalized with carboxylic groups as starting reagent. The acid groups were firstly converted in acyl chloride moieties and afterwards were bound to hexamethylenediamine (HMDA) via formation of amide functionality. The acquired spectra of attenuated total reflectance and the analysis performed through x-ray photoelectron spectroscopy confirmed the amide bond formation. The hyperbranched polymer characterization was completed by using scanning and transmission electron microscopy, thermo-gravimetric analysis and Raman spectroscopy. The electron microscopy analyses showed the formation of an amorphous polymeric material englobing a dense network of SWCNTs without phase segregation, demonstrating that the reaction with HMDA allows a reorganization of SWCNTs in a complex three-dimensional network.

Amorphous magnetic Fe–Co–Ni–Si–B films have been produced on silicon and glass substrates by means of XeCl excimer laser ablation of amorphous magnetic ribbons. Laser fluence, the number of pulses, and target–substrate distance were the variable parameters. The films were studied with x-ray specular reflectivity, x-ray diffraction, x-ray photoelectron spectroscopy, profilometry, and ellipsometry. Laser ablation has been found to provide a good transfer of composition and structure from the ribbon targets to the deposited films, with excellent mechanical and optical quality of the films. Magnetic properties of the films were examined by a technique based on the magneto-optical Kerr effect. The films revealed well-defined in-plane uniaxial anisotropy. They demonstrated coercivity and anisotropy field values comparable to those of the initial ribbons, and much higher steepness of substantially rectangular hysteresis loops. The films can have a number of prospective applications in magnetic sensors, switches,...

The hydrogen desorption from MgH 2 – Mg 2 NiH 4 phase mixtures prepared under different ball milling conditions has been investigated and correlated with the samples microstructure. SEM, XRD and XPS were performed to explore the microstructure in order to ascertain the reciprocal influence of the two phases on the de-hydrogenation reaction, and in particular on the hydrogen desorption temperature. Ball milling imparts different microstructures to the phase mixtures according to the adopted processing parameters. The resulting microstructure influences the hydrogen desorption which appears to occur by a limited number of well-defined channels at characteristic temperatures. A microstructural interpretation of this behavior is proposed on the basis of the characterization results. From the applicative point of view it is possible to notice that this mixture, when properly processed, shows a onset temperature of the desorption of the whole hydrogen content about 150 K lower than MgH 2 , even on samples exposed to the atmosphere.

The production of II–VI semiconductor compound – polymer matrix nanocomposites by a direct in-situ thermolysis process is described. Metal-thiolate precursor molecules embedded in a polymer matrix decompose by a thermal annealing and the nucleation of semiconductor nanocrystals occurs. It is shown that the nucleation of nanoparticles and the formation of the nanocomposite can be also achieved by laser beam irradiation; this opens the way towards a “lithographic” in-situ nanocomposite production process. A possible growth and nanocomposite formation mechanism, describing the structural and chemical transformation of the precursor molecules, their decomposition and the formation of the nanoparticles, is presented. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Thin ZrN x O 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 ZrO 2 , 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.

Hydrogen generation by catalytic hydrolysis of sodium borohydride (NaBH 4 ) is studied by using Co–B-based thin film catalyst synthesized by pulsed laser deposition (PLD) technique. Co–B nanoparticles, produced in the catalyst film after the laser ablation process, act as active centers producing significantly higher H 2 generation rate than Co–B bulk powder. Surface morphology was studied by using scanning electron microscopy and compositional analysis was established by using X-photoelectron and infrared spectroscopies. Films were deposited at different PLD set-up parameters in order to understand the possible role of size and density of the nanoparticles in the catalytic process. Cobalt has been found here to act as an efficient catalyst only when alloyed with boron which partially prevents cobalt oxidation. In particular we report that when used as suitable thin films, Co–B produces H 2 with a maximum generation rate of about 3300 ml/min per gram of catalyst.

Thin ZrNx films have been prepared by reactive radiofrequency magnetron sputtering varying the nitrogen partial pressure in the range 0–3.26 Pa. The films have been analyzed by X-ray photoelectron spectroscopy (XPS) and by optical characterization in the UV–Vis–IR range. The cross-section and surface morphology of the samples were examined by means of field emission gun–scanning electron microscopy. The effects of the nitrogen partial pressure on the ZrNx films stoichiometry have been studied correlating the N 1s photoelectron peaks with different bounding states for the zirconium nitride. The XPS depth profile analysis has revealed the presence of metastable phases (ZrN2, Zr3N4) that vanishes when lowering the nitrogen partial pressure. The optical analysis has permitted to distinguish two different behaviours of the deposited samples in the visible range: semi-transparent and absorbent. Drude–Lorentz model fitted the behaviour of absorbent films, while the O'Leary model was applied to the semi-transparent ones. The semi-transparent films had a band gap varying between 2.36 and 2.42 eV, typical values of N-rich zirconium nitride films. Morphological analysis showed a compact and dense columnar structure for all the samples. A simple growth model explains the presence of the different nitride phases considering implantation and re-sputtering effects.

Thin ZrN x films have been prepared by reactive radio frequency magnetron sputtering. The radio frequency power has been chosen as a sputtering parameter and the effect on the compositional and optical properties of the films was systematically studied. The films have been analyzed by X-ray photoelectron spectroscopy. The reflectance and transmittance of the samples have been recorded by a spectrophotometer in the UV–Vis–IR range. The effects of the different powers (in the range 100–400 W) on the stoichiometry of ZrN x films have been studied. The components revealed on N 1s photoelectron peaks were correlated with different bounding states for the zirconium nitride. The threshold power value between N-rich ZrN x films and Zr-rich ZrN x ones is 270 W. A correlation has been observed between the optical properties and the stoichiometry of the films. In fact, the samples catalogued as N-rich by X-ray photoelectron spectroscopy analyses are optically insulating and the Zr-rich ones show a metallic behaviour. A simple growth model has been set up in order to explain the different chemical states detected from the compositional measurements.

Mg-graphite composites, suitable for hydrogen storage, have been synthesized by ball milling metallic Mg with different amounts of graphite and benzene. The microstructure and the surface chemical composition have been characterized in order to explain the kinetics of reaction with hydrogen. The presence of benzene in the milled blends induces a finer powder particle size, helps to preserve the structural integrity of the graphite crystals and results to be necessary for a complete transformation of the milled powder to the hydride phase by thermal reaction with hydrogen gas. On the other hand, it induces a more pronounced reaction of the milled Mg-C composites with the air. The transport properties of the resulting surface contamination layer appear to control the kinetics of thermal decomposition of the MgH2 phase, so that the addition of benzene induces a higher reaction temperature owing to a larger thickness of the surface compound. (c) 2006 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.

Cadmium sulfide (CdS) and zinc sulfide (ZnS) nanocrystals were grown following three different chemical synthesis routes. In particular, the nanocrystals were synthesized by in situ thermolysis (∼300 °C) starting from a metal thiolate (i) in a solventless way, (ii) by a novel route in trioctylphosphine oxide (TOPO), and (iii) by direct synthesis in a polystyrene matrix. The formation of cadmium sulfide (zinc sulfide) nanocrystals and the chemistry of the organic/nanocrystal (polymer/nanocrystal) composites were investigated in detail by X-ray photoelectron spectroscopy (XPS). In addition, X-ray diffraction analyses (XRD) were performed in order to determine the crystallographic structure and the average size of the nanocrystals. The precursor powders (Cd(SR) 2 and Zn(SR) 2 ) of both II-VI compounds were analysed after annealing in different atmospheres (air, nitrogen, vacuum) at 300 °C (in situ thermolysis) in order to establish the starting of the nanocrystal formation process. All the three chemical routes employed and investigated here, showed the formation of CdS (and ZnS) nanocrystals. X-ray diffraction analyses evidenced that under optimized growth conditions single crystal nanoclusters of zinc-blende structure and of diameter between ∅=1.5 and 3.0 nm (depending on the annealing temperature and time) are formed. Very good and promising results were obtained by the novel route in TOPO that revealed that sulfur has only one component on the S 2p unresolved doublet (at about 161.6 eV ± 0.2) associated to the metal-sulfide bond, i.e. the Cd(Zn)-S nanocrystals are capped by metal-sulfide-TOPO chains. CdS and ZnS nanocrystals embedded in a polystyrene matrix were also successfully prepared and the XPS analyses revealed, in particular, that the sulfur doublet signal is split at least into two peaks, compatible with S in CdS structure and with S bonded to organic residues with energies of 161.66 and 166.98 eV respectively.

Cadmium sulfide nanoparticles embedded in a polystyrene matrix (CdS/PS) were successfully prepared by in situ thermolysis of a cadmium thiolate precursor dispersed in the polymer. The heat-induced formation of cadmium sulfide was studied by thermogravimetric analysis and differential thermal analysis, while the chemistry of the reaction forming the CdS/PS compound was investigated by nuclear magnetic resonance and X-ray photoelectron spectroscopy. The structural characterization was performed by X-ray diffraction and transmission electron microscopy. The CdS nanocrystals are single crystals of cubic phase (zincblende structure) of spherical shape. The average diameter of the nanocrystals embedded in the polystyrene matrix achieved by our synthesis process is as small as 2.5 ± 0.5 nm. Room temperature UV–VIS absorption spectra exhibit a shoulder at 412 nm that is consistent with the presence of CdS nanocrystals of ∅ ≈ 2 nm. The role of the polymer on the nanoparticle growth was also discussed.

The hydrogen storage performances of Mg-C nanocomposites have been studied on materials synthesized by ball milling with and without addition of an organic additive. The main purpose of this work is to study in more detail the cooperative effect observed when both graphite and benzene are added to the milled blend. In fact, when both components are added to Mg in the ball milling process, good catalyzing properties of the composite surface allow improved sorption-desorption behavior of the synthesized material. The processed materials have been characterized by XRD to assess the details of the phase structure by Rietveld analysis, while surface features have been studied by XPS, which evidences structural modifications of both the surface Mg oxide and the graphite particles. The hydrogen desorption behavior has been correlated with the surface structure which appears to depend on the carbon to benzene ratio. Thermal stability and hydrogen desorption properties were investigated by DSC. Experimental results on nanocomposites with the same Mg to C weight ratio (70:30) show improved performances for a proper choice of carbon to benzene ratio weight (1/3), even after manipulation of the milled material in air. Current Research in Advanced Materials and Processes, 6th Conference of the Yugoslav-Materials-Research-Society, Sep 13-17, 2004, Herceg Novi, Montenegro

Ion implantation of titanium nitrite (TiN) coatings attracts a great deal of attention because of the improvement of tribological resistance of the coating surface. In this work we have analysed implanted TiN films by using secondary ion mass spectrometry (SIMS). Coatings with a thickness of about 4 μm were implanted with C + at energies of 100 keV and fluences ranging from 10 16 to 7 × 10 17 ions/cm 2 . The experiments were performed on commercial TiN films prepared by physical vapour deposition (PVD) on hard metal tools. If reactive elements, like C or N, are implanted to significative fluences, the implant concentration (say greater than 1 at.%) could induce a distortion in the experimental elemental profiles because of a change in the sputtering yield and/or the ionisation probability (matrix effects). While the first point has been shown to be largely insignificant, the second is studied in more detail. In the case of carbon implanted in TiN the influence of matrix effects on the secondary ion signals can be minimised if a primary beam of Cs + and secondary negative ions are chosen for depth profiling up to fluences of technological interest, say 3 × 10 17 ions/cm 2 . In this way the concentration changes induced in the ion implanted region can be quantified. Linear calibration curves were obtained for an accurate quantification and X-ray photoelectron spectroscopy (XPS) was employed to extract the starting stoichiometry in the unimplanted TiN film and to assess the chemical state along the depth profiles in the implanted samples. After implantation a swelling of the films was observed and has been discussed. SIMS profiles were measures both by cesium and oxygen primary beams.

A chloride-based inorganic sol-gel route was used for preparing pure and metal (osmium, nickel, palladium, platinum)-doped SnO 2 sol. SnCl 4 was first reacted with propanol, then the resulting compound was hydrolyzed and subsequently mixed with solutions of the metal dopants. The obtained sols were used for depositing thin films by spin coating or for preparing powders by solvent evaporation at 110°C. FTIR spectroscopy and thermal analysis of the powders revealed that chlorine still bound to tin stabilized the sol against gelation by hindering the condensation reactions. Film characterizations showed that platinum and palladium, unlike nickel and osmium, were likely to form nanoparticles in the SnO 2 lattice. This result was discussed with regard to the different ways that platinum and palladium, on one hand, and nickel and osmium, on the other, modified the growth of SnO 2 grains and the film roughness and morphology. Dopants that formed nanoparticles (platinum, palladium) resulted in the roughest film, while dopants that did not form particles (nickel, osmium) resulted in SnO 2 grain size very close to that of pure SnO 2 .

The investigation of the surface and interface of a multilayer coating is a key factor for producing high quality optical device. In this work, we present a non-destructive technique as X-ray reflectivity to study deeply the chemical and structural quality of the multilayer. XPS depth profile analysis and AFM images have been used to evaluate the chemical intermixing and the surface roughness in order to verify the X-ray results.

Different methods have been proposed to reduce the surface thrombogenicity of small caliber vascular grafts, using plasma treatments of polymer surfaces in order to improve the adhesion and the proliferation of human endothelial cells (HEC). Plasma modified polyethyleneterephthalate (PET) substrates were employed to grow HEC, isolated from the umbilical vein. A combination of X-ray photoelectron spectroscopy (XPS) and Sessile contact angle (SCA) measurements allowed the study of the surface modifications produced soon after nitrogen and hydrogen plasma treatments with respect to an untreated PET substrate, used as reference. It was possible to select a number of PET substrates while actually performing the HEC seeding experiments. The HEC proliferation was evaluated by light microscope image analyzes. ©2000 Kluwer Academic Publishers

The hydrogen desorption from MgH2–Mg2NiH4 phase mixtures prepared under different ball milling conditions has been investigated and correlated with the samples microstructure. SEM, XRD and XPS were performed to explore the microstructure in order to ascertain the reciprocal influence of the two phases on the de-hydrogenation reaction, and in particular on the hydrogen desorption temperature. Ball milling imparts different microstructures to the phase mixtures according to the adopted processing parameters. The resulting microstructure influences the hydrogen desorption which appears to occur by a limited number of well-defined channels at characteristic temperatures. A microstructural interpretation of this behavior is proposed on the basis of the characterization results. From the applicative point of view it is possible to notice that this mixture, when properly processed, shows a onset temperature of the desorption of the whole hydrogen content about 150 K lower than MgH2, even on samples exposed to the atmosphere.

ITO thin films have been deposited onto glass substrates by sequential reactive evaporation as transparent and conductive electrodes for devices. The method has the advantage of low enough temperatures (≤200°C) for the processes of preparation and post-annealing, accurate control of single layer thickness, simplicity and low cost. ITO films with electrical resistivity of 10 −2 Ω cm and optical transparency greater than 90% have been obtained. The structural, compositional, electrical, optical properties of the films depend on the annealing time. The stability of the electrical and optical properties of the electrodes has been investigated showing the feasibility of producing high quality ITO films by this method.

Pb(Zr,Ti)O3 (PZT) oriented films deposited by laser ablation on Au(111)/Si(111) have been tested by different techniques for their physico-chemical homogeneity. The samples have been divided in different zones, in order to verify the existence of chemical and structural differences between different regions. Few techniques like X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) have been employed for characterization. XRD analyses showed differences regarding the crystallographic content and the degree of orientation between zones subjected to the plasma arriving at different angles of incidence on the sample surface. In the same zones XPS studies have been performed by a VG ESCALAB 210 Spectrometer, using a non-monochromatic AlKα X-ray source (300 W) in the five channel hemispherical analyzer. Wide scans in the binding energy scale 0–1200 eV, at 50 eV analyzer pass energy, were collected both from the as received surface and after sputter cleaning in order to put into evidence all the constituents of the film. Narrow scans of Ti 2p, Zr 3d, Pb 4f and O 1s were also acquired at 20 eV and 0.1 eV/channel pass energy and 100 ms of dwell time in order to give a better insight into the chemical bonds form and a semiquantitative analyze of the present chemical species. The piezoelectric properties of different zones were also measured.

WO3 thin films have been deposited by reactive rf sputtering onto low-cost glass substrates as gas sensitive coatings. The properties of the grown films have been investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS) in order to characterize their structure, composition, surface chemistry. The d.c. electrical response to different gases of the WO3 thin films has been measured in the temperature range from 100 to 400°C showing an increase of electrical resistance with a good sensitivity towards NOx gas at 250°C. WO3 thin films oppositely detect also NH3, H2, H2S, SO2 gases by decreasing the electrical resistance and are practically insensitive to interfering gases like CO, CH4 in the same temperature range. The sensing characteristics of the NOx gas detector based on tungsten trioxide (WO3) thin films are reported.

In this work, we present a detailed structural and microanalytical study of BaCuO2/CaCuO2 superlattices grown on (001) SrTiO3 substrates by pulsed laser deposition technique. Our analyses were performed by using high-resolution x-ray diffraction, reciprocal space mapping, x-ray specular reflectivity, and x-ray photoelectron spectroscopy. We found that the BaCuO2/CaCuO2 superlattices are grown pseudomorphically on the SrTiO3 substrate. X-ray photoelectron spectroscopy measurements show that the Ca is partially oxidized having both Ca–O and Ca–Ca bonds, while Ba is completely oxidized (Ba–O bonds). The results of our analyses demonstrate that the pulsed laser deposition technique allows one to fabricate high quality infinite-layer superlattices of high structural and chemical ordering.

High quality AlN thin films were grown at 200–450°C on sapphire substrates by laser ablation of Al targets in nitrogen reactive atmosphere. The nitrogen pressure was varied between 10 −3 and 10 −1 mbar. The reactive gas pressure during irradiation and the temperature of the substrate were found to essentially influence the quality of the layers. X-ray diffraction analysis evidenced the formation of highly orientated layers for a very restrictive set of parameters. Other analysis techniques, like X-ray photoelectron spectroscopy, secondary ion mass spectroscopy, optical transmission spectroscopy have been used to evidence the good stoichiometry and purity of the films. The characteristics of these films were compared with those of AlN thin films deposited in similar experimental conditions, on Si (100) and Si (111) substrates.

A detailed structural characterization of SrCuO 2 /CaCuO 2 infinite layer superlattices is presented. The analyses are performed by using high-resolution X-ray diffraction, reciprocal space mapping and X-ray specular reflectivity. In addition, preliminary results of X-ray photoelectron spectroscopy are reported. The X-ray analyses confirm the high structural quality of infinite layer superlattices deposited by pulsed laser technique on slightly misoriented SrTiO 3 substrates. The strain analyses indicate that (i) a macroscopic tilt of the superlattice with respect to the substrate lattice occurs, and (ii) the SrCuO 2 layers are in a relaxed state, while the CaCuO 2 unit cells are tetragonally distorted with respect the SrCuO 2 lattice. The low-angle X-ray measurements reveal good interfacial properties and indicate a partial correlation of the interface roughness across the layers. A computer simulation of the experimental X-ray specular reflectivity patterns yields an average interface roughness of about 4 A. Finally, the X-ray photoelectron spectroscopy investigations confirm the good quality of the infinite layer superlattices with a correct stoichiometric contents and, particularly, a chemical state of CuO 2 planes similar to that of typical high quality superconducting YBCO thin films.

Reactive ion beam assistance appears to be a useful technique to fabricate optical coatings with the correct stoichiometry. The bombarding ions modify the composition of the growing film principally by the preferential sputtering of the film atoms and by the implantation of the ions themselves. Investigation of these effects is necessary to obtain a desired composition of the coating. In this work, a set of titania films was grown by sputtering from a Ti target and simultaneously bombarding the titanium with a low energy (300 eV) oxygen and argon ion beam. X-ray photoelectron spectroscopy was used to measure the film composition at the surface as-grown and after sputtering for 30 min in situ. In particular, it was seen that the oxygen content increases for an increased oxygen-to-argon flux ratio. In particular, the oxygen content in the film is constant for an oxygen-to-argon flux ratio greater than 0.8. The experimental results for film composition are in agreement with the results obtained by a simple model, developed in this work, to describe the ion assistance phenomena and to estimate the partial sputtering yields.

Crystalline AlN thin films were deposited by laser ablation of high purity Al target in nitrogen reactive atmosphere. An YAG laser (λ=1.06 μm, tFWHM=10 ns, 0.3 J/pulse), was used as laser source. The material was collected on (100) and (111) Si wafers, The target collector distance was varied in the range 3–6 cm, the nitrogen pressure was set in the range of 10−3–10−1 mbar, the collectors were heated at different temperatures between 20 and 350°C. The influence of the process parameters on the physical and piezoelectric properties of the deposited films was analyzed. X-ray diffraction studies revealed different crystalline orientation depending on deposition conditions: collectors temperature, position and orientation, reactive gas pressure, incident laser fluence. The profile of Al and N atoms inside the film were characterized by SIMS analysis. Small oxygen traces are present at collector–film interface. Depth profile X-ray photoelectron spectroscopy confirms the existence — in particular experimental conditions — of only Al–N bonds inside the film.

Materials Science Forum, A.M. Mancini, C. Paorici e M.L. Terranova eds.

TiAlN/AlN multilayers are attracting great interest for the possibility to modulate their mechanical and tribological properties through the variation of multilayer design. In this work TiAlN single layer, TiAlN/AlN intermixed-multilayer and nano-multilayer were prepared using a reactive magnetron sputtering system starting from targets of TiAl and Al. The aim is to analyze how the multilayer design affects the thermal and tribological properties of the coatings. The microstructure of as-deposited and annealed films has been studied using X-ray diffraction. The chemical composition has been deduced by XPS analyses. Thermal behavior was assessed by means of differential thermal analysis (DTA) and thermogravimetric analysis (TGA), while mechanical properties have been investigated by wear tests. © 2013 The Authors.

Homogeneous nanocomposite silica films uniformly doped with size-selected gold nanoparticles (AuNPs) have been prepared by a combined use of colloidal chemistry and the sol‐gel process. For this purpose, stable thiol-functionalized AuNPs (DDT-AuNPs) were first synthesized by a two-phase aqueous/organic system and, subsequently, dispersed in an acid-catalysed sol‐gel silica solution. The microstructural morphology of the samples was investigated by x-ray diffraction and field emission scanning electron microscopy. X-ray photoelectron spectroscopy (XPS) and UV‐vis optical spectrophotometry were instead employed to investigate the elemental chemical behaviour and the evolution of the surface plasmon resonance (SPR) band of the AuNPs from their synthesis up to the formation of the Au-doped silica films. The results show that the size, shape and crystalline domains of the AuNPs remain unchanged during the entire preparation process, indicating that their aggregation or decomposition was prevented. XPS results show that the DDT-AuNPs lose the capping shells and oxidize themselves when dispersed in acid-catalysed sol‐gel solutions, and that bare AuNPs are embedded in the SiO2 films. A large broadening of the SPR band, observed for systems with DDT-AuNPs, suggests the presence of interface effects which cause a surface electron density lowering. Thiol chain detachment from the AuNPs determines an increase of the SPR peak intensity while the oxidation of the Au surfaces causes a red shift of its position. The latter is no longer observed in doped films, suggesting that no interfacial effects between bare AuNPs and the host medium are present. (Some figures in this article are in colour only in the electronic version)

Scanning electron microscopy observations, energy dispersive spectroscopy, x-ray diffraction and x-ray photoelectron spectroscopy analyses have been employed to study the composition and the microstructure of titanium carbonitride coatings deposited by a reactive ion-plating industrial system. Both TiN and Ti(C, N) coatings show a very fine and dense microstructure and consist of a NaCl-type single phase with a marked preferred orientation. X-ray photoelectron spectroscopy analysis of the characteristic Ti, C and N lines establishes the extent of Ti(C, N) compound formation and the dependence of composition on the reactive gas flow ratio. Depth profiles obtained by XPS analyses after cycles of Ar+ sputtering indicate chemical uniformity of the films. Microhardness measurements taken on coated HSS specimens show that Ti(C, N) are significantly harder than TiN and TiC films deposited under the same conditions. Ti(C, N) coatings have a lower coefficient of friction and a higher wear resistance than TiN coatings, irrespective of the mating material.

In this paper, we report the successful growth of c-BCN thin films by reactive pulsed laser ablation (RPLA) of a rotating target (3 Hz) formed of two semidisks: one of h-BN and the other one of graphite, with the substrate at room temperature. The irradiations were performed in vacuum (10 -5 Pa) and in N 2 ambient gas (1-100 Pa) using a XeCl excimer laser ( A = 308 nm, τ FWHM = 30 ns) with a fluence of 5 J/cm 2 . Series of 10,000 pulses at a repetition rate of 10 Hz were directed to target. Different analysis techniques pointed out the synthesis of h-BCN and c-BCN. Microhardness measurements at the deposited films evidence high values up to 2.9 GPa. Secondary ion mass spectroscopy (SIMS) profiles showed the presence of layers of 600-700 nm thickness, with uniform concentrations of B. C and N in the films. Uniform signals of BN and CN. which are related to the BCN bond, are also present. X-ray photoelectron spectroscopy (XPS) studies pointed out the BCN compound formation. The deconvolution of B Is recorded spectra evidenced a strong peak (centered at 188 eV) assigned to B bonded in BC 2 N: the N Is and C Is spectra also confirm the BCN formation. Transmission electron microscopy (TEM) and selected area electron diffraction (SAED) analysis evidenced the presence of c-BCN phase (with crystallites of 30-80 nm) and h-BCN phase as well. The N 2 pressure strongly influenced the BCN formation and, consequently, the properties of the deposited films.

In this study, nitrogen-doped titanium dioxide (TiO2) powders were synthesized in two ways: by heating of titanium hydroxide with urea and by direct hydrolysis of titanium tetraisopropoxicle (TTIP) with ammonium hydroxide. The samples were characterized by structural (XRD), analytical (XPS), optical (UV/Vis absorption/reflection and Raman spectroscopy) and morphological (SEM, TEM) techniques. The characterization suggested that the doped materials have anatase crystalline form without any detectable peaks that correspond to dopants. The absorption threshold of titanium dioxide was moved in the visible range of optical spectrum from 3.2 eV to 2.20 eV. Particle sizes of synthesized powders were obtained from XRD measurements and from TEM data ranging from 6-20 nm. XPS and Raman spectroscopy were used for detection of nitrogen in doped samples. International Workshop on Nanostructured Materials (ANAOMAT 2006), Jun 21-23, 2006, Antalya, Turkey

Pd and Ag nanocrystals of diameter 1-30 nm embedded in amorphous silica matrix have been prepared by the sol-gel process. In order to correlate the preparation route to the structural and optical properties of the materials and to obtain a deeper insight in the formation and physical properties of the clusters, a detailed structural and optical characterization have been undertaken via transmission electron and high resolution electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, optical spectroscopy and differential scanning calorimetry. In the case of Pd and PdO, the sol-gel process has been modified by using organofunctional silanes. Thick film and uncracked bulk materials containing uniformly dispersed Pd nanocrystals are obtained by this technique after thermal treatment up to 400 degrees C. The Pd to PdO phase transformation following the annealing beyond 400 degrees C in air is also studied.

Microstructure and surface chemistry of nanocomposites prepared by ball milling metallic Mg with different amount of graphite and benzene has been characterized and correlated to hydrogen sorption behavior.

We report on the synthesis and microstructural and microanalytical analysis of dodecanethiol and benzylthiol-stabilized Au nanoparticles (diameter range between 2 nm and 10 nm). Stable functionalized gold nanoparticles were synthesized by using two different routes: a two-phase liquid-liquid method and a one-phase method. The size, strain, shape and crystalline structure of the nanocrystals were determined by a full-pattern X-ray powder diffraction analysis and high-resolution electron microscopy. The chemical environment of the Au nanocrystals and their interaction with the thiols was investigated by X-ray photoelectron spectroscopy. Photoluminescence spectroscopy measurements show a characteristic IR emission at λ=960 nm of small sized Au nanocrystals (∼3 nm). The origin of this IR emission line seems to be correlated to the Au-S bonding and the size of the nanoparticles.

In this work we report on the growth of cadmium sulfide and zinc sulfide nanocrystals by thermolysis, starting from a metal thiolate in a (i) solventless way, (ii) by a novel route in tryoctilphosphine oxide (TOPO), and (iii) by direct synthesis in a polystyrene matrix. The x-ray diffraction (XRD) and transmission electron microscopy (TEM) show that the nanocrystals fabricated by the different methods are under optimized growth conditions single crystals of zincblende structure and of regular spherical shape. The average size was estimated to be between 2.0-3.0 nm with a size dispersion that depends on the synthesis route and is in the range between 10% and 20%. The XPS results indicate that for the nanoparticles obtained via solventless strategy the sulfur is present both as bonded to the metal atom and to the organic residue, while in the TOPO synthesized nanoparticles the sulfur signal has only one component associated to the metal-sulfide bond. The photoluminescence spectroscopy (PL) analysis of CdS crystals clearly evidences the typical emissions of nanosized zincblende CdS monocrystalline particles. Furthermore, the optical spectroscopy data indicate that the size distribution of the Cdsulfide - TOPO nanoparticles seems to be generally larger than that ones grown directly in polymer matrix. For all the CdS samples, the metal-sulfide nanocrystals exhibit a trap-related radiative transition at about 2eV that can be attributed to the hole-electron recombination at particle surface defect-center.

Different methods have been proposed to reduce the surface thrombogenicity of small caliber vascular grafts, using plasma treatments of polymer surfaces in order to improve the adhesion and the proliferation of human endothelial cells (HEC). Plasma modified polyethyleneterephthalate (PET) substrates were employed to grow HEC, isolated from the umbilical vein. A combination of X-ray photoelectron spectroscopy (XPS) and Sessile contact angle (SCA) measurements allowed the study of the surface modifications produced soon after nitrogen and hydrogen plasma treatments with respect to an untreated PET substrate, used as reference. It was possible to select a number of PET substrates while actually performing the HEC seeding experiments. The HEC proliferation was evaluated by light microscope image analyzes.

A molybdenum chloromethoxide was prepared by reaction Of MOCl5 with methanol. By water addition, a sol was obtained that was stable on a month time scale. The sols were characterized by UV-vis and Raman spectroscopy, showing that upon water addition hydrolysis takes place but without extensive condensation, explaining the sol stability. The sol was modified by addition of cetyltrimethylammonium bromide to get deposition of thin films onto silicon substrates. Very uniform, polycrystalline alpha-MoO3 thin films on silicon or polycrystalline powders could be obtained after heat treatment at 350degreesC of the as-deposited film and the evaporated sol, respectively. Fourier transform infrared and X-ray photoelectron spectroscopy studies on the films and powders have shown that, while the films are extensively polymerized after the deposition and chlorine free, the powders evolve with the heating temperature toward the final structure by a stepwise process in which the Mo(IV) and Mo(V) states are progressively oxidized to the final Mo(VI) state. The powders heated at at least 250degreesC are chlorine free. X-ray diffraction patterns measured on thin films and powders show that the films are amorphous up to 250degreesC, while powders begin to crystallize as alpha-MoO3 at such a temperature. These results are supported by thermal analysis on powders. Scanning electron microscopy observations show that the film morphology is initially very smooth while after heating at 500degreesC it is constituted by flat micrometric platelets. The powders heated at 500degreesC show a lamellar structure.

In the last years lead zirconate titanate (PZT) thin films have been widely studied for their use in piezoelectric and ferroelectric thin films devices. For many applications it is important to have relatively large film area with homogeneous properties. We prepared PZT thin films by pulsed laser deposition in reactive O/sub 2/ atmosphere, by using a Nd:YAG laser (/spl lambda/=1060 nm, /spl tau//sub FWHM/=10 ns, 0.3 J max. energy/pulse, 10 Hz). Au coated Si(111) substrates were heated at approx. 370/spl deg/C, while the O/sub 2/ atmosphere value was maintained at 0.15 mbar. The targets were sintered PZT ceramics disks with Pb(Zr/sub 0.4/Ti/sub 0.6/)O/sub 3/ composition. The obtained films were tested in different zones by few techniques, like XRD, XPS and local piezoelectric coefficient measurements. XRD analysis shown that the structure of the films in all zones was pseudo-perovskite with (111) orientation, but differences in the crystallographic content and the degree of orientation of zones subjected to plasma flux regions arriving at different angles of incidence on sample surface were found. In the same zones XPS studies were performed by using a non-monochromatic Al K/spl alpha/ X-ray source. Scans of Ti2p, Zr3d, Pb4f, O1s were acquired and information about the chemical bonds formed and the compositions in each zone were obtained. The d/sub 33/ piezoelectric coefficient was locally measured and correlated with chemical and structural film properties. Samples with homogeneous properties were selected and employed in the construction of acceleration sensor devices. Results on response and sensitivity of constructed devices are presented and discussed.

Failures of small internal diameter vascular grafts have been caused by the lack of a stable endothelial lining to form on their artificial surfaces. Polymer surfaces can be optimized by means of proper treatment to allow a homogeneous and uniform coverage in artificial prosthesis applications. Several solutions were studied to improve cell attachment and growth on artificial materials. In the present study, polyethyleneterephthalate (PET) surfaces were treated by plasma processes with oxygen and ammonia and also in the presence of a gas mixture to verify the effect of functional groups grafting onto the endothelial cell growth. Related surface chemical modifications were investigated by X-ray photoelectron spectroscopy (XPS). Then using cytotoxicity and cytocompatibility tests, the biocompatibility of the modified PET surfaces was assessed by studying the behavior of human umbilical vein endothelial cells (HUVEC). The results showed that plasma-treated PET samples have no toxic effect on HUVEC. The cytocompatibility tests revealed an increase in cell growth with incubation time and the presence of well-spread and flattened cells (SEM analyses). Thus it is reported that plasma treatments can improve PET biocompatibility to HUVEC.

Using different correlated techniques, we addressed the problem of the uniformity of the properties of piezoelectric thin films obtained by pulsed laser deposition, with particular emphasis on lead zirconate titanate thin film. This problem is presented together with a survey of different experimental findings and in the context of existing theoretical models. The results allow us to define a uniform deposition area over which properties like film thickness, composition, crystalline structure and piezoelectric properties remain almost constant in the selected experimental conditions.