G. Mattogno

XPS study of apatite-based coatings prepared by sol-gel technique

Abstract Biocompatible layers of hydroxyapatite and fluorhydroxyapatite were grown on Ti substrates by means of dip-coating into sol–gel. In order to improve the adhesion of apatite-based coatings, the substrates were a priori covered with calcium titanate. Therefore, the hydroxyapatite, fluorhydroxyapatite and CaTiO 3 coatings were produced and analysed. The chemical composition of the coatings (CaTiO 3 , CaTiO 3 +hydroxyapatite, and CaTiO 3 +fluorhydroxyapatite) was studied by using X-ray photoelectron spectroscopy (XPS). The data of quantitative XPS analysis displayed the different features (cleanness, homogeneity, etc.) of CaTiO 3 , hydroxyapatite, and fluorhydroxyapatite films after the growth and after the treatment in vitro.

Properties of CuxS thin film based structures: influence on the sensitivity to ammonia at room temperatures

Abstract Surface and electrical properties of thin CuxS films grown on different substrates (polyethylene and micro-porous-Si layer) sensitive to ammonia at room temperature are investigated. The resistance response to ammonia is measured in the CuxS in air with relative humidity from 15 to 100% at temperatures from 290 to 350 K. The surface chemical composition and the morphology are analysed. A honeycombed construction of the CuxS films deposited on a micro-porous Si-layer and proportions between components in the chemical composition are found to correlate with the higher sensitivity to ammonia in air at room temperature.

Surface analysis of biocompatible coatings on titanium

The coatings of hydroxyapatite, which is widely used for orthopaedic and dental prothesis, were deposited by using the dip-coating method. The layers of hydroxyapatite were grown on commercial Ti substrates. In order to improve the adhesion of hydroxyapatite, the substrate was a priori covered with titania or calcium titanate by using the sol-gel technique. For comparison, commercial samples of hydroxyapatite coating (manufactured by means of plasma-spray apparatus) were analysed. The chemical composition and the structure of the coatings (TiO2, CaTiO3 and hydroxyapatite) were studied by using X-ray photoelectron spectroscopy (XPS), scanning Auger microscopy (SAM), X-ray diffraction (XRD) and secondary electron microscopy (SEM) techniques. The data of quantitative XPS analysis and the surface images (SAM and SEM) displayed the superior quality (cleanness, homogeneity, etc.) of hydroxyapatite deposited by sol-gel in comparison with commercial samples investigated.

Surface studies of in vitro biocompatibility of titanium oxide coatings

Titanium oxide coatings are normally used for orthopaedic and dental prostheses. Nevertheless, their chemical, biological and mechanical properties can be still improved by the development of new preparation technologies. In this paper a surface characterisation of the titanium oxide layer, grown on commercial Ti substrates by metal organic chemical vapour deposition (MOCVD) technique, is reported. The biocompatibility of the samples is tested upon in vitro treatment as a function of the exposure time. The surface characterisation of the titanium substrate and the oxide coatings is performed by using different analytical techniques. Surface chemical composition and morphology of the coatings are investigated by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and scanning tunnelling microscopy (STM). Quantitative XPS analysis and surface physical images show a good quality (cleanness, homogeneity, roughness) of the oxide coating deposited by MOCVD and the surface modifications induced by the interaction with osteoblast cells.

Hydroxy- and fluorapatite films on Ti alloy substrates: Sol-gel preparation and characterization

In this paper we describe the preparation of hydroxyfluorapatite (HFA) and fluorapatite (FA) films deposited on titanium alloys by means of the dip-coating method starting from a sol-gel prepared colloidal solution. These materials are compared with hydroxyapatite (HA) films prepared via sol gel and commercial films prepared by means of plasma spray. The film characterization from the point of view of the composition and crystallinity, performed by means of XRD, FTIR and Raman Spectroscopies, has shown a good purity degree, and compositional homogeneity for the sol-gel materials, though traces of carboxy-hydroxy apatite were found. Also, the samples exhibit a good crystallinity. SEM pictures, taken on HA coating deposited via sol-gel, revealed a homogeneous surface structure and optimum features to set up a good prosthesis-tissue interface.

Metal complexes of dithiocarbazic acid and its derivatives—I: Ni(II) and Zn(II) complexes of N-substituted dithiocarbazic acids

Abstract The complexes of nickel and zinc with ligands RR′NNHCS2− (R = H, R′ = C6H5; R = R′ = CH3; R = R′ = C6H5; R = CH3, R′ = C6H5), NH2NRCS2− (R = H, CH3, C2H5, n-C3H7, n-C4H9) and CH3NHN(CH3)CS2− have been prepared. Generally low-spin complexes of MeL2 type have been obtained, but high-spin complexes of Ni(II)L3 type have been also obtained with NH2NHCS2− and (CH3)2 NNHCS2− ligands. The substitution on N atoms in the dithiocarbazato ligand exerts a deep influence in its coordinating ability leading to complexes with N, S or S, S coordination.

Interaction of mercury vapour with thin films of gold

Thin films of gold deposited on a silicon substrate were used as electrical sensors of mercury vapour. The samples were exposed to mercury vapour at room temperature, changing the Hg concentration and the exposure time. The chemical composition and morphology of the films exposed to mercury vapour were studied by X-ray photoelectron spectroscopy (XPS), secondary ion mass spectroscopy (SIMS), scanning Auger microscopy (SAM) and secondary electron microscopy (SEM). In the samples exposed for a short time, the mercury was adsorbed by thin surface sublayer of Au film. In the case of long exposures, the transformation of the uniform Au film to a dendritic-like coalesced AuHg amalgam occurred, i.e. the morphology of the film was modified irreversibly. This transformation is caused by insufficient adhesion of gold to the substrate.

XPS investigation on vacuum thermal desorption of UV/ozone treated GaAs(100) surfaces

Abstract In order to prepare suitable surfaces for molecular beam epitaxy (MBE), sacrificial thin oxide layers on HCl etched GaAs(100) surfaces were grown by both air and UV/ozone exposure. Passive films were subsequently removed by vacuum thermal desorption to achieve surfaces that were smooth and clean on an atomic scale. The evolution of the surface chemical composition, as a function of vacuum desorption temperature, has been studied by means of X-ray photoelectron spectroscopy (XPS). XPS results have evidenced for air and UV/ozone exposed GaAs(100) surfaces a relationship between desorption temperature and surface chemical composition; indeed, the oxide removal is temperature dependent and sequentially selective as follows: As2O3. AsO and Ga2O3. Furthermore, XPS results have shown that air-grown films have a chemical composition and thermal desorption behaviour different from UV/ozone treated materials. Indeed, these latter have an As2O3/Ga2O3 and an unoxidized As/Ga ratio close to unity for as grown and thermal treated at 580°C surfaces, respectively. By contrast, air-exposed GaAs(100) materials are Ga2O3-enriched and after vacuum thermal desorption treatments have never a stoichiometric composition(As(GaAs)/Ga(GaAs)= 1). Furthermore UV/ozone treated GaAs(100) surfaces subjected to a vacuum thermal treatment at 580°C, have a troublesome organic contamination level below XPS detectability, whereas from air-exposed surfaces, carbon is not completely thermally removable

Peculiarities of surface doping with Cu in SnO2 thin film gas sensors

It is demonstrated that a small amount of Cu impurity (less than 1 at.%) significantly modifies the properties of tin oxide thin films used for the gas sensors. Different amount of Cu (between 0.5 and 7 at.%) was sputtered on the top of the films. The structure, surface chemical composition, optical and electrical properties are studied for these films. It is shown that the surface doping with the sputtered Cu leads to nearly constant doping level in all the volume of the polycrystalline tin oxide thin film. It is shown experimentally that the selectivity of the resistance response to CO, H2 and Cl2 gases is improved for the tin oxide sensors by the small amount of the sputtered Cu. A correlation is revealed between the Cu effect and the electronic surface states that were detected by the XPS and the optical analysis.

Surface characterization of biocompatible hydroxyapatite coatings

The coatings of hydroxyapatite are widely used for orthopaedic and dental prostheses. Nevertheless, their chemical, biological and mechanical properties still can be improved by the development of new preparation technologies. Here we report a surface characterization of hydroxyapatite coatings prepared by different deposition techniques. The layers of hydroxyapatite are grown on commercial titanium substrates by using sol-gel and electrodeposition techniques. The biocompatibility of the samples is tested upon in vitro treatment as a function of the exposure time. Surface chemical composition and morphology of the coatings are studied by means of x-ray photoelectron spectroscopy (XPS), scanning Auger microscopy (SAM) and scanning electron microscopy (SEM). Quantitative XPS analysis and surface chemical and physical images reveal different features (cleanness, homogeneity, roughness) of the coatings and different surface modifications induced by the interaction with osteoblast cells.