Search results for "photoemission spectroscopy"
showing 10 items of 108 documents
Refractory metal reactivity towards oxide surface : W/TiO2(1 1 0) case.
2006
International audience; Reactivity of deposited tungsten towards TiO2(1 1 0) surface was studied using synchrotron radiation photoemission spectroscopy (both core levels, valence band and resonant photoemission) on Materials Science Beamline at ELETTRA. W depositions carried out at room temperature on TiO2(1 1 0) surface give rise to an interfacial reaction which leads to a metastable situation due to kinetic limitations. Annealing induces chemical changes which are function of the initial coverage; for fractional coverage, annealing induces completion of oxidation of deposit whereas reduction to metallic tungsten occurs for highest coverage. These results demonstrate that interaction of W …
Inhibition of Cor-Ten steel corrosion by “green” extracts of Brassica campestris
2018
Abstract Extract of Brassica campestris was tested as potential corrosion inhibitor for Cor-Ten steel in NaCl and acidic solutions, simulating a marine and an urban-industrial environment, respectively. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were performed both in absence and in presence of the extract at room temperature. The surface chemical analysis was investigated by X-ray Photoemission Spectroscopy (XPS), before and after corrosion. Electrochemical results demonstrated that a very small concentration of Brassica campestris extracts can inhibit Cor-Ten corrosion in NaCl solution (inhibition efficiency of 80–84%) better than in acidic solutions. Su…
Direct observation of half-metallicity in the Heusler compound $Co_{2}MnSi$
2014
Ferromagnetic thin films of Heusler compounds are highly relevant for spintronic applications owing to their predicted half-metallicity, that is, 100% spin polarization at the Fermi energy. However, experimental evidence for this property is scarce. Here we investigate epitaxial thin films of the compound Co2MnSi in situ by ultraviolet-photoemission spectroscopy, taking advantage of a novel multi-channel spin filter. By this surface sensitive method, an exceptionally large spin polarization of () % at room temperature is observed directly. As a more bulk sensitive method, additional ex situ spin-integrated high energy X-ray photoemission spectroscopy experiments are performed. All experimen…
Aging of the surface of an Al-Cr-Fe approximant phase in ambient conditions: Chemical composition and physical properties
2003
ABSTRACTWe have investigated the surface properties of quasicrystalline and approximant phases in the Al-(Cu)-Cr-Fe system upon aging in ambient conditions. We found that some of these properties (like the electrochemical behavior, wetting or friction) slowly evolves with the length of exposure to normal atmospheric conditions, reaching a stable state only after several days. This report essentially focuses on one of these alloys, an Al65Cr27Fe8 approximant phase with g-brass structure. In a first part, we describe the effect of aging on the electrochemical behavior of this alloy and we propose an interpretation based on a simple electrical model of the oxidized surface. In a second part, w…
Structure and chemical bonds in reactively sputtered black Ti–C–N–O thin films
2011
The evolution of the nanoscale structure and the chemical bonds formed in Ti–C–N–O films grown by reactive sputtering were studied as a function of the composition of the reactive atmosphere by increasing the partial pressure of an O2+N2 gas mixture from 0 up to 0.4 Pa, while that of acetylene (carbon source) was constant. The amorphisation of the films observed by transmission electron microscopy was confirmed by micro- Raman spectroscopy, but it was not the only effect associated to the increase of the O2+N2 partial pressure. The chemical environment of titanium and carbon, analysed by X-ray photoemission spectroscopy, also changes due to the higher affinity of Ti towards oxygen and nitro…
Non-linear optical study of hierarchical 3D Al doped ZnO nanosheet arrays deposited by successive ionic adsorption and reaction method
2020
Abstract Successive ionic layer adsorption and reaction (SILAR) method is based on the adsorption and reaction of the ions in the cationic solution and the ionic solution, respectively. This method is simple, inexpensive, large-scale deposition, effective way for deposition on 3D substrates, low-temperature process and represents an easy way for the preparation of doped, composite and heterojunction materials. To take advantage of this method and the ZnO nanostructures, various parameters have been optimized. Undoped and Aluminum (Al) doped ZnO nanostructures were prepared by the SILAR technique. The characterization of the nanostructures prepared was carried out using X-ray diffraction (XR…
Influence of the Chemical Dissolution of MnS Inclusions on the Electrochemical Behavior of Stainless Steels
2005
Immersion of stainless steel containing a well-controlled density of MnS inclusions in 1 M NaCI, pH 3 leads to the chemical dissolution of these heterogeneities. This process was studied using in situ atomic force microscopy and the dissolution rate of MnS inclusions was estimated between 0.01 and 0.19 μm 3 /min. The effects of MnS dissolution on the chemical composition and the local electrochemical behavior of the specimen surface were investigated using secondary ion mass spectroscopy, X-ray photoemission spectroscopy, and the electrochemical microcell technique. It was shown that stable CrS and unstable FeSO 4 were formed. The size of the areas around MnS inclusions affected by the pres…
Stabilisation of tetragonal zirconia in oxidised ZrSiN nanocomposite coatings
2004
Abstract ZrSiN coatings were deposited on steel and silicon substrates by reactive sputtering of a composite ZrSi target. The coatings were oxidised in air in the 600–750 °C temperature range. As-deposited and oxidised films were characterised by X-ray diffraction, micro-Raman spectroscopy, X-ray photoemission spectroscopy and glow discharge optical emission spectroscopy. The oxidation behaviour of ZrSiN coatings was compared to that of ZrN ones. It was demonstrated that addition of silicon in the 3–5 at.% range into ZrN-based coatings promotes the onset of oxidation by nearly 100 °C. The structure of the oxide layer was strongly dependent on the film’s silicon content: monoclinic zirc…
Chemical stability of the magnetic oxide EuO directly on silicon observed by hard x-ray photoemission spectroscopy
2011
We present a detailed study of the electronic structure and chemical state of high-quality stoichiometric EuO and O-rich ${\mathrm{Eu}}_{1}{\mathrm{O}}_{1+x}$ thin films grown directly on silicon without any buffer layer using hard x-ray photoemission spectroscopy (HAXPES). We determine the EuO oxidation state from a consistent quantitative peak analysis of $4f$ valence band and $3d$ core-level spectra. The results prove that nearly ideal, stoichiometric, and homogeneous EuO thin films can be grown on silicon, with a uniform depth distribution of divalent Eu cations. Furthermore, we identify the chemical stability of the EuO/silicon interface from Si $2p$ core-level photoemission. This work…
Angle resolved X-ray photoemission spectroscopy double layer model for in situ characterization of metal organic chemical vapour deposition nanometri…
2007
International audience; In situ Angle Resolved X-ray Photoemission Spectroscopy (ARXPS) characterizations of TiO2 thin films grown on silicon by Metal Organic Chemical Vapour Deposition were performed in order to get information on interfacial reactions at the first stages of the growth, one of the aims being to understand the influence of deposition conditions. Thickness measurements were also carried out from ARXPS analyses. As the real structure of the films was shown to be a double layer system such as TiO2/SiO2/Si, an ARXPS model of thickness and surface coverage determination was applied to each layer independently. However, the application of this model to very thin films underestima…