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Titanium tetraisopropoxide (TTIP) molecules have been deposited on the copper substrate Cu(111) with monolayer coverage at cryogenic, room and elevated temperatures and studied by variable temperature scanning tunneling microscope (STM), X-ray photoelectron spectroscopy (XPS), low electron energy diffraction (LEED) and X-ray absorption near edge structure (XANES) spectroscopy using the synchrotron radiation. Adsorption and irregular assembling of entire molecules are observed at low temperatures. At room temperature, STM reveals an agglomeration of TTIP molecular fragments. The XPS analysis confirms presence of ligand groups bonded to molecular center, indicating a partial decomposition process up to 670 K. TTIP molecules start to decompose completely on copper surface at elevated temperatures, higher than 800 K. Hexagonal surface oxide structure is formed after TTIP monolayer thermal decomposition at 870 K, as it is proved by LEED and STM.

In this study, we report transmission electron microscopy and electron energy loss spectroscopy study of cerium oxide thin layer grown on graphite foil substrate by direct liquid injection chemical vapour deposition. Transmission electron microscopy experiments have revealed the porous morphology of the deposited layer. Energy electron loss spectroscopy measurements were also performed in scanning mode to study the evolution of the cerium valence. In addition to Ce 4+ inside the layer, the presence of reduced cerium oxide with Ce 3+ valence is pointed out at the layer surface and at the surface of the porosity developed by the layer. Besides, studies of high resolution images coupled to electron energy loss spectroscopy have indicated the presence of crystallized ceria nanoparticles, and the absence of cerium carbide.

Nanocomposite films composed of gold nanoparticles (AuNPs) embedded in a TiO 2 matrix have been prepared by direct liquid injection chemical vapor deposition process, using preformed nanoparticles and titanium isopropoxide as precursors. The spherical AuNPs about 4.1 nm in diameter were synthesized by using gold (III) chloride trihydrate and stabilized by thiol ligands. The depositions were carried out by performing at first oxide deposition, then gold nanoparticle one and capping with oxide. The morphology, structure; the chemical state and optical properties of nanocomposite films were characterized by scanning electron microscopy, Raman, X-ray photoelectron and UV–Vis absorption spectroscopies, respectively. The stability of the films upon thermal annealing up to 800 °C was studied.

Porous cerium oxide thin films were grown by pulsed direct liquid injection metal organic chemical vapor deposition (DLI-MOCVD) on silicon substrate, using cerium tetrakis (1-methoxy-2-methyl-2-propanolate) dissolved in cyclohexane as precursor as well as oxygen as oxidant agent. The chemical and morphological characteristics of the films were investigated by XPS, SEM and TEM. The influence of the growth conditions on the morphological features of the thin films and the cerium chemical states are reported and discussed. The decrease of the oxygen and/or alkoxide flow rate induces the decrease of both the film thickness and the porosity of the layer. Moreover, the growth of silicate at the interface between the silicon substrate and the grown film is evidenced.

Nanostructured Pt–TiO 2 composite thin films were synthesized by direct liquid injection metal organic chemical vapor deposition process, using trimethyl(methylcyclopentadienyl)platinum and titanium isopropoxide as precursors. Surface and cross-sectional morphologies obtained by scanning electron microscopy and transmission electron microscopy evidenced the uniform distribution of platinum nanoparticles in the TiO 2 matrix. At higher Pt content, the X-ray diffraction analysis showed that the face-centered cubic phase of platinum appeared together with an anatase TiO 2 structure. In addition, as far as the platinum chemical state is concerned, the co-deposition of TiO 2 and Pt allowed obtaining Pt 2 + or Pt°, in a ratio strongly dependent on the Pt content. Indeed, X-ray photoelectron spectroscopy characterization evidenced the presence of only Pt 2 + for lower Pt content and only Pt° for higher one. The variation of platinum content in the TiO 2 films resulted in a change of the chemical state of platinum.

Deposition of tungsten carbide (WC) films was investigated by radio-frequency reactive sputtering using a tungsten target and methane gas. The effect of some processing parameters (pressure, power, CH 4 -to-Ar gas flow ratio) upon the chemical and structural properties of the films has been investigated. The evolution of the chemical composition has been analyzed by photoemission, the microstructure has been studied through electron microscopy techniques and the crystallographic structure was investigated by X-ray diffraction as well as Raman spectroscopy. This study demonstrates that the formation of tungsten carbide is highly dependent on the deposition conditions: thin films are composed of either metallic tungsten or carbon for a total gas pressure of 0.5 Pa while for higher total gas pressure (5 Pa), tungsten carbide films are deposited for a large power range (50–180 W) but a narrow range of methane flow rate (2–8%). In this latter case, no changes are observed in microstructure and crystallography of tungsten carbide films with processing parameters: all films present a columnar growth and are mainly formed of cubic sub-stoichiometric WC 1 − x nanocrystallites embedded in amorphous carbon. However, as function of process parameters, a strong variation in chemical composition of the films is revealed and is attributed to the defective structure of cubic sub-stoichiometric WC 1 − x phase.

Thin films of Pt-doped CeO 2 were grown by direct liquid injection chemical vapor deposition on silicon wafer covered by native oxide at 400 °C using Ce(IV) alkoxide and organoplatinum(IV) as precursors. X-ray photoelectron spectra evidenced that the platinum oxidation state is linked to the deposition way. For platinum deposited on top of cerium oxide thin films previously grown, metallic platinum particles were obtained. Cerium and platinum codeposition allowed obtaining a Pt 0 and Pt 2 + mixture with the Pt 2 + to Pt ratio strongly dependent on the platinum flow rate during the deposition. Indeed, the lower the platinum precursor flow rate is, the higher the Pt 2 + to Pt ratio is. Moreover, surface and cross-sectional morphologies obtained by scanning electron microscopy evidenced porous layers in any case.

In this study, we report transmission electron microscopy and electron energy loss spectroscopy study of cerium oxide thin layers deposited on silicon substrate. Transmission electron microscopy experiments have revealed the flat morphology of the deposited layers. In addition, studies of high resolution images have indicated the presence of mainly ceria crystallized nanoparticles. Energy electron loss spectroscopy measurements were also performed in scanning mode to study the evolution of the cerium valence. In addition to Ce4+ inside the layer, the presence of amorphous cerium silicate with valence +3 is pointed out at the vicinity of the substrate.

Laser ablation of metallic targets in gas atmospheres gives rise to the formation of nanoparticle (NP) powders when high laser irradiances (i.e., > 1 GW/cm² for aluminium targets) are used. The properties of the NPs so formed vary as a function of the laser irradiation parameters and the pressure and composition of the ambient gas. Here, we studied the composition and structure of NPs formed by laser ablation of Al targets with a nanosecond Nd:YAG laser emitting at 1064 nm. The laser irradiance was 2.5 GW/cm2. N2–O2 gas mixtures containing different amounts of nitrogen (100–80 vol% N2) were used as ambient gas at atmospheric pressure. The influence of the ambient gas composition on the morphology and the structure of the NPs was studied ex-situ by scanning and transmission electron microscopy, X-ray diffraction and micro-Raman spectroscopy. Their composition of light elements was determined by ion beam analysis. It was shown that together with metallic aluminium, different amounts of aluminium nitride and aluminium oxynitride were formed in the NPs as a function of the nitrogen concentration in the ambient gas. Below 95 vol% N2, the concentration of nitride phases decreases strongly. However, the formation of aluminium oxide (Al2O3) was not observed, whereas it was detected in NPs formed in air. A discussion of these results that takes into account the dynamics of the plasma plume is proposed.

In this study, the characterization of nanostructured Pt-doped CeO2 films with low platinum content and porous structure is reported, deposited on silicon substrate by direct liquid injection chemical vapor deposition. The platinum localization and concentration in the nanocomposite are determined by scanning transmission electron microscopy associated with energy dispersive X-ray spectroscopy. Films are made of approximate to 3 nm diameter CeO2 particles and platinum is homogeneously dispersed through the layers. X-ray photoelectron spectroscopy (XPS) also shows that platinum is mainly in an ionic Pt2+ state. After diffusion through the preformed porous structure of ceria films, the platinum precursor decomposes at the surface of each ceria particle forming the films, producing a homogeneous platinum-doped CeO2 nanocomposite. This result is supported by synchrotron radiation XPS experiment, where the measured relative Pt concentration demonstrates that platinum is decomposed only at the surface of ceria particles. Finally, when the saturation of Pt2+ sites at the surface of ceria particles is reached, metallic nanoclusters are formed from platinum excess.

The thermal behavior of the titanium–tungsten adhesive layer (30–70 at.%) deposited on a SiO2 substrate followed by a thicker Pt layer was investigated. The resulting Pt/TiW/SiO2 planar system was annealed under air or vacuum. Morphological and chemical characterizations at different stages of the annealing, as a function of several parameters such as treatment atmosphere, annealing temperature and thickness of the Pt film were performed through surface science analyses. When annealing under air, even at mild temperature (773 K), the whole interlayer oxidizes while a low amount of tungsten diffuses through platinum film. This phenomenon is related to tungsten oxidation which acts as the driving force leading to WO3 ultra thin overlayer. On the obtained WO3/Pt/TiO2–WO3/SiO2 system, whatever subsequent vacuum annealing conditions are, the reduction process of surface tungsten oxide is revealed leading to WOx

Sol-gel x TiO 2 (100 − x )SiO 2 nanocomposite thin films with x = 0, 25, 50, 75 and 100 mol % were dip-coated on glass and silicon substrates. The influence of the composition on structure, morphology and optical properties was studied by X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, scanning electronic microscopy, monochromatic ellipsometry at λ = 632.8 nm and ultraviolet–visible absorbance spectroscopy. The optical properties were discussed on the basis of the microstructure. After annealing at 500 °C, results showed high pure materials, homogenous crack-free surfaces with good adherence and high optical qualities. The 100% TiO 2 crystallizes in the anatase phase and exhibits nanograins of 6 to 10 nm in size. However, all the other compositions are amorphous with comparable grains around 4 nm in size. The averaged transmittance decreases with increasing the TiO 2 content but remains higher than 90%. Whatever the composition, the coating thickness increases linearly as the withdrawal speed increases from 10 to 54 mm/minute. The relationship between refractive index and composition was analyzed by fitting the experimental data to different theoretical models for the refractive index of mixed films. Results showed that depending on the withdrawal speed, the data can properly fit either the Drude or the linear models. Thus, the film thickness can be adjusted by the control of the withdrawal speed. However, the control of the composition allows easily the tuning of the refractive index from 1.48 to 2.18 at λ = 632.8 nm to achieve optimum anti-reflection characteristics. Different anti-reflection designs of both single and double layers were experimentally examined. Gains (assigned to the reduction of reflection losses) up to 54 and 63% were predicted with 75% TiO 2 single-coating and SiO 2 /TiO 2 double-coatings respectively.

The present work investigated the thermal stability of tungsten–titanium diffusion barrier layers intercalated between SiO 2 substrate and platinum thin film. The resulting structures were annealed under air in the temperature range 400–600 °C for annealing times up to 100 h. Chemical and structural characterizations at different stages of the treatment evidenced several phenomena occurring during annealing under air, especially the complete oxidation of the adhesive layer, the diffusion of tungsten oxide through platinum film at particle boundaries as well as the sublimation process of tungsten oxide. The results of film surface chemistry and microstructure were correlated with diffusion phenomena.

The thermal stability of Pt/Ti–W/SiO2 system was studied after annealing under air or vacuum in the present work. A Ti–W adhesive film (30 at. % Ti) was deposited on a SiO2 substrate followed by a thicker Pt layer. Depositions were performed using DC magnetron sputtering. The whole as-deposited films are metallic with a columnar growth of platinum deposit which totally wets the substrate. Whatever the atmosphere is, annealing at 500 °C for 12 h does not change the platinum state but modifies the morphology of platinum particles, the lateral average size of which increasing from less than 10 nm up to ca. 75 nm. Besides, a noticeable diffusion of metallic tungsten through Pt film is revealed for annealing carried out under vacuum. When annealing under air, oxygen diffusion through the Pt layer causes an oxidation of the whole Ti–W interlayer, inducing an important volume increase and degraded interfaces. Such an oxidation process comes with the migration of WO3 species through Pt-grain boundaries, up to the Pt surface. As the width of Ti–W interlayer is increased, a higher amount of WO3 reaches the surface, ultimately leading to discontinuities of the Pt layer.

The surface of Cu(111) was exposed to molybdenum hexacarbonyl Mo(CO)6 with monolayer coverage at temperature 160 K and studied by a Scanning Tunneling Microscope. The monolayer structure has a hexagonal arrangement and forms a (√7 × √7) R19 superlattice on the copper (111) plane. Upon repeated scanning the monolayer is transformed into a (1 × 2) superstructure with 3-fold oriented domains. The domains of (1 × 2) superstructure can change orientation under scanning according to 3-fold surface symmetry. From analysis of the domain mobility, it follows that CO groups of carbonyl fragments are organized in the (1 × 2) superstructure conditioning the domain reorientation. The observed structure transformation under scanning is a result of stimulated dissociation of molybdenum hexacarbonyl on the copper surface.

We studied in this work the influence of the wavelength (532 vs. 1064 nm) on the insertion of nitrogen in titanium targets by surface laser treatments in air. The laser pulses were of 5 ns and the irradiance was lower than 25 × 10 12 W/m 2 . Results obtained using a frequency-doubled Nd:YAG laser at 532 nm were compared with those previously reported for laser treatments at 1064 nm. Nuclear reaction analysis and micro-Raman spectroscopy were used for determining the composition and the structure of the surface layers, respectively. Results showed the lower efficiency of irradiation at 532 nm for nitrogen insertion, which is possible only above threshold conditions depending on both the laser irradiance and the number of cumulated impacts per point. This was explained as being due to a higher ablative effect in the visible range. The insertion of oxygen giving rise to the growth of titanium oxynitrides was also discussed.

The combination of photoelectron diffraction, density functional theory, and multiple scattering calculations is used for a quantitative analysis of the widely debated structure of ${\mathrm{TiO}}_{2}$ (011). The modeling of the diffraction patterns for different surface reconstructions allows one to discriminate the key structural constraints required or, on the contrary, prohibited in the reconstruction of this termination. In particular, photodiffraction rules out previously proposed reconstructions while it evidences the key feature of the ${\mathrm{TiO}}_{2}$ (011) termination: an oxygen splitting induced by missing rows.

Barium was deposited at room temperature on a thermal silicon oxide layer and the interfacial reaction was monitored by synchrotron induced photoemission (both core level and valence band). The first step of the growth consists of an interfacial reaction which leads to the formation of an interfacial silicate layer. The next step consists in formation of barium oxide while metallic barium occurs subsequently. The deposit can be also homogenized by annealing above 575 K. This results in the formation of several layers of silicate by consumption of silicon oxide. In the case of fractional coverage, subsequent annealing at 975 K induces the decomposition of barium silicate. However, such a decomposition process is strongly dependent on the initial film thickness. It can be avoided for deposits thicker than 3 eqML.

Nickel was deposited on stoichiometric TiO2(1 1 0) surface in the 0.02–2.1 equivalent monolayer (eqML) range and analyzed by means of photoemission and resonant photoemission. In the case of very low coverage (lower than 0.1 eqML), deposited nickel reacts with the surface through an electronic transfer from nickel atoms towards titanium ions. This exchange caused the filling of unoccupied Ti3d states leading to the increase of a peak in the TiO2 band gap. These states can be better characterized through resonant photoemission experiments at the Ti 3p → 3d absorption edge: for very low coverage, these states in the TiO2 band gap have resonant behavior of Ti3d electrons rather than Ni3d ones, confirming the filling of Ti3d states and thus electron transfer between nickel and titanium. For coverage higher than 0.14 eqML, nickel peaks (both Ni3p core level and valence band) should be related to the presence of metallic nickel in small clusters.

International audience; WO3 nanorods are grown by a simple vapor deposition method on a mica substrate and characterized by Selected Area Electron Diffraction and Energy Dispersive X-rays Spectroscopy. Experimental results show the clear evidence of an unexpected WO3 hexagonal structure as well as an epitaxial growth on the mica substrate. Besides, potassium is evidenced inside the nanorods. It is thus deduced that a metastable WO3 hexagonal phase is stabilized by epitaxy through a tungsten bronze interlayer having same hexagonal structure.

Accepted manuscript, Direct current reactive magnetron sputtering was implemented to successfully deposit dark Ti(C,O,N) thin films on silicon substrates. A titanium target was sputtered while a mixture of oxygen and nitrogen was injected into the deposition chamber, independently from an acetylene source. The deposition parameters were chosen as a function of pre-existing knowledge about sputtered Ti–O–N and Ti–C–O films. Tuning the oxygen/(nitrogen+carbon) ratio allowed obtaining a large spectrum of properties. In particular, the colour of the films was characterized by spectral reflectance spectroscopy, and expressed in the CIE 1976 L*a*b* colour space. An accurate control of the reactive gas mixture flow rate allowed obtaining intrinsic, stable and attractive dark colour for decorative applications. Surprisingly, the coatings with the lowest content of carbon and the highest content of oxygen presented the darkest tones. Composition analysis by electron probe microanalysis was done to quantify the titanium and metalloid concentrations in the films. X-ray diffraction experiments revealed the evolution of the film structure from a fcc structure for the lowest (O2+N2) flow rates to an amorphous one for the highest flow rates., Fundação para a Ciência e Tecnologia (FCT) - SFRH/BPD/27114/2006 and PTDC/CTM/69362/2006. CRUP (Acção Integrada Luso-francesa No. F-2307). GRICES/CNRS collaboration (Proc. 4.1.1 França)

Excess electrons profoundly affect the properties of oxide surfaces. The present review deals with excess charges on rutile and anatase. These much studied titania polymorphs open with strong prospects regarding (photo)catalysis and dye-sensitized solar cells. In the complex landscape of the mechanisms of electron trapping and electron transfer toward adsorbates, excess electrons open with flexible model systems which are the focus of an extensive research effort.

In situ chemical surface analyses using X-ray photoelectron spectroscopy (XPS), completed by ex situ atomic force microscopy (AFM) analyses, were performed in order to compare the initial stages of MOCVD growth of TiO 2 thin films on two different surface types. The first type was a silicon native oxide free hydrogen terminated surface and the second one was a silicon dioxide surface corresponding to a thin layer of 3.5 nm thick in situ thermally grown on silicon substrate. Si(100) was used as substrate, and the growths of TiO 2 thin films were achieved with titanium tetraisopropoxide (TTIP) as precursor under a temperature of 675 °C, a pressure of 0.3 Pa and a deposition time of 1 h. Whatever the surface is, the deposited titanium amount was globally the same in the two cases. On the contrary, the deposit morphology was different: a covering layer composed of a SiO 2 and TiO 2 phases mixture on the hydrogen terminated surface, and small TiO 2 clusters homogeneously spread on the SiO 2 surface.

The rutile TiO 2 (1 1 0) surface is a highly anisotropic surface exhibiting “channels” delimited by oxygen rows. In previous experimental and theoretical DFT works we could identify the molybdenum adsorption sites. They are located inside the channels. Moreover, experimental studies have shown that during subsequent annealing after deposition, special molybdenum nano structures can be formed, especially two monolayer high pyramidal chains of atoms. In order to better understand the dynamics of nano structure formation, we present a kinetic Monte Carlo study on diffusion and adsorption of molybdenum atoms on a TiO 2 (1 1 0) surface. A quasi one-dimensional lattice gas model has been used which describes the possible adsorption sites of a Mo atom in a single channel of the surface. The atomic positions of a 1.5 monolayer thick Mo film formed of pyramidal chains define the lattice sites of the model. Thereby the formation of three-dimensional clusters could be studied. Here we have studied the cluster formation as a function of parameters that can be controlled in a growth experiment by physical vapor deposition: deposition and annealing temperature, flux and total amount of deposited Mo. Good qualitative agreement with recent experiments is obtained.

K-edge X-ray absorption and 2p-XPS spectra of 3d-element oxides present spectral features which cannot be explained within a simple one-electron model. These features reveal the fine electronic structure of transition metal (TM) oxides valence states resulting from hybridized TM-3d and O-2p states, and the correlations between these valence electrons. In this paper, we show how resonant electronic spectroscopy (resonant Auger or resonant photoelectron spectroscopy) around the TM K-edge can be used to interpret the structures of the threshold and, with the help of theoretical calculation, to determine the electronic configuration of the excited ion. Quadrupolar transitions towards localized 3d orbitals are hence detected and quantitatively characterized in the titanium K-edge prepeaks in TiO2 and in the Ni K-edge prepeaks in NiO by angular-dependent resonant KLL Auger measurements. Valuable information also seems to be available in the resonant behavior of 2p-XPS spectra of NiO and Fe2O3.

Small amounts of molybdenum (from 0.03 to 1.3 eqML) were deposited on non-stoichiometric TiO 2 (1 1 0) surface. The deposits were investigated by means of LEED and X-ray/UV photoemission using synchrotron radiation. For the smallest coverage (

Undoped TiO 2 and Ag–TiO 2 (up to 23 at.% Ag) cermet thin films and polycrystalline powders have been prepared by sol–gel process. Their structure, composition, surface morphology and optical properties have been investigated by X-ray diffraction (XRD), differential thermal analysis (DTA), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS) and ultraviolet–visible spectroscopy (UV–VIS spectroscopy). It has been observed that while Ag does not form a solid solution with TiO 2 , it promotes the anatase to rutile phase transformation. The transformation temperature decreases from 827 °C for undoped TiO 2 to about 650 °C for 23 at.% Ag-doped TiO 2 . SIMS analyses show that Ag is mostly present on the surface of the films. XPS studies confirm that these Ag are in the Ag 0 state. Optical analyses show that with increasing Ag content, the refractive index ( n ) increases and the optical absorption behavior of the cermet films is modified, but the band gap of the anatase TiO 2 is not influenced.

In situ chemical surface analyses using X-ray photoelectron spectroscopy (XPS) were performed to understand the initial stages of TiO 2 thin-film MOCVD growth. Deposits on Si (1 0 0), a few nanometres thick, were obtained at a fixed temperature of 650 °C and for two different pressures, 2.9 and 0.05 mbar, using titanium tetraisopropoxide (TTIP) as precursor. Pressure lowering led to a higher deposit growth rate. Reduction of titanium with respect to stoichiometric titanium dioxide and oxidation of the wet-cleaned silicon substrate are observed from decomposition of the Ti 2p and Si 2p peaks. The formation of a TiSi x O y mixed oxide is also pointed out and confirmed by the presence of a characteristic component in the O 1 s peak.

The interfacial reaction between deposited molybdenum and three different TiO2(1 1 0) substrates (a bulk and surface stoichiometric TiO2; a bulk stoichiometric and surface reduced crystal; a bulk and surface slightly reduced crystal) was investigated by means of X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge spectroscopy (XANES). While the interfacial reaction is not a function of the substrate at room temperature (in any case, molybdenum layers grow with oxygen dissolved in), this study clearly reveals a strong effect of the substrate bulk stoichiometry on the chemical state of the deposit after annealing up to 750 °C whereas the substrate surface stoichiometry plays a minor role. Indeed, annealing carried out on deposits performed on bulk stoichiometric TiO2 (whatever the initial surface stoichiometry is) leads to MoO3 formation whereas annealing carried out on layers which grew on bulk non-stoichiometric TiO2 involves metallic molybdenum overlayers. These results, as well as others previously published on the same system, are discussed from a new model based on thermodynamical considerations including entropic effect.

Resonant electronic spectroscopy consists in measuring a non-radiative decay process (Auger or autoionization process) excited with photon energies around an absorption edge. The resonant spectra carry information both on the nature of the electronic transitions near the absorption edge by scanning the very first empty orbitals above the Fermi level (through the absorption process), and, on the other hand, on the atomic electronic configuration through the lineshape of the observed decay process. In this paper, after a quick review of the pioneering works in this field, we show that resonant measurements and their theoretical modeling can be used to precisely interpret complex absorption spectra. Hence, Ce resonant 3d photoemission spectra allow, in the Ce-L3 edge, to attribute the two white lines to 4f1 and 4f0 final state electronic configurations and to evidence the presence of a hidden 4f2 structure in the rise of the absorption threshold. Quadrupolar transitions towards localized 3d orbitals are also detected and quantitatively characterized in the titanium K-edge prepeaks in TiO2, thanks to angular dependent resonant Ti-KLL Auger measurements.

The adsorption site of sodium on the TiO2(1 1 0)–(1 × 1) surface was studied by extended X-ray absorption fine structure. For coverage ranging between 0.25 and 0.5 ML, we find that sodium is on an ‘in-between' site where it is bound to two bridging oxygen atoms at 2.25 Å and one in-plane oxygen atom at 2.40 Å, in full agreement with DFT calculations. At higher coverage the site becomes an hollow site where the sodium atom is equidistant to the three oxygen atoms at 2.30 Å, while metallic sodium clusters are also formed at the surface.

Molybdenum has been deposited at room temperature on stoichiometric TiO 2 (1 1 0) surfaces with two deposition rates: 0.1 equivalent monolayer (eqML) and 1.5 eqML min −1 . X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy studies clearly reveal an effect of the deposition rate upon the growth mode and the interfacial reaction. Indeed, whereas a strong interfacial reaction between Mo and TiO 2 involves a Stranski–Krastanov growth mode with the formation of amorphous molybdenum oxide monolayers for the lowest deposition rate, no reaction can be observed for the highest deposition rate. Moreover in this latter case, the growth mode seems to be a 3D one. These differences are discussed from a pure kinetics point of view.

This study is concerned with the growth and characterization of metallic gallium 3D structures, obtained with a single growth step, by the LP-MOCVD technique on various substrates. Commercial organo-metallic is used as gallium precursor and nitrogen as carrier gas. The growth temperature and the reactor pressure are ranking between 500 and 700 °C, and between 150 and 700 torr, respectively. Depending on the elaboration conditions, different 3D structures are obtained such as droplets, cauliflowers, aggregates or thin stems, with micrometer sizes. The morphology, substrate surface density and thermal stability are studied by optical and scanning electron microscopy. At last, X-ray microanalysis and X-ray diffraction are carried out in order to determine the elemental composition and the crystallographic structure of these 3D objects. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

This paper presents the growth and characterization of metallic gallium three-dimensional (3D) structures and preliminary results of their transformation into GaN-like structures. The structures were grown by metal-organic vapour phase epitaxy (MOVPE), using trimethyl gallium as gallium precursor on silicon (1 0 0). The growth temperature was between 550°C and 750°C. Interesting and new metallic structures were obtained with our growth parameters: balloon (montgolfier-like structure) and cauliflower-like. These metallic structures can grow up perpendicular to the substrate surface and have diameters between 0.1 and 5 μm, depending on the growth conditions. Moreover, selective metallic growth was obtained with our growth conditions. Some discussions about the growth mechanism are also presented. The Ga 3D nitridation process was carried out by annealing under NH 3 between 650°C and 750°C, far below the conventional nitridation temperature in MOVPE. Preliminary X-ray diffraction results show that a GaN-like structure can be obtained at such low nitridation temperature.

GaAs (100) substrates have been heat-treated in a metal-organic chemical vapor deposition reactor under flows of NH 3 and an oxygen organo-metallic precursor at temperatures between 650°C and 750°C. Yellowish films formed at the surface of all the samples. Gallium, nitrogen and oxygen were detected by EDX analysis of the films. The oxygen content was estimated in the range of at 5-10 at% depending on the heat-treatment temperature. X-ray diffraction and HRTEM results indicate that the structure of the films corresponds to the hexagonal wurtzite phase of GaN with an expanded unit cell. Raman spectra show hands corresponding to the Raman active GaN modes as well as disorder-activated broad bands below 450 cm -1 related to the oxygen content in the films.

Background: Off-target verbosity (OTV), defined as prolific speech that is lacking in focus, is exhibited by relatively few older adults, but increases in prevalence with age. Objective/Methods: The hypothesis that a high level of OTV is associated with declining competence in other aspects of everyday life was examined in 142 older adults, previously screened for the level of OTV. Competence was assessed based on self-reported changes since age 50 years in quality and quantity of engagement in eleven domains of instrumental and voluntary activities of everyday life. Results: Path models indicated that a high level of OTV was associated with a decreased competence in everyday activities and was indirectly linked, through competence, with lower well-being and greater loneliness. With competence level controlled, a high level of OTV directly predicted less loneliness. Conclusions: These findings support the hypothesis that a high level of OTV is symptomatic of a more general decline in competence and of less successful aging. However, a high level of OTV also entails a strong motivation for talking to others and thus may offer protection against loneliness.

Molybdenum films were deposited at room temperature on rutile TiO2(1 1 0) surfaces having different stoichiometries, surface roughnesses and crystallinities. The film structures and compositions and the substrate–film interfaces were investigated by X-ray diffraction, high-resolution transmission electron microscopy and energy-dispersive X-ray spectroscopy. Different substrate pretreatments resulted in markedly different film and interface structures. Under the growth conditions studied, no amorphous molybdenum oxide interlayers were formed upon deposition in contrast to previous studies. Preferred (1 1 0) textured Mo films grew on both air-annealed and oxygen-bombarded substrates. While sharp substrate–film interfaces were observed in the air-annealed samples, oxygen bombardment led to a rough interface. Epitaxial growth was achieved on argon-bombarded substrates, and a single crystal TiO interlayer was present as a result of the substrate pretreatment. The orientation relationship among three crystalline layers was: Mo(2 0 0)[0 0 1]//TiO(2 0 0)[0 1 1]//TiO2(1 1 0)[0 0 1]. Even though the growth was epitaxial, the argon bombardment resulted in a rough interface between the substrate and the TiO interlayer and between TiO and the Mo film. The results are compared with previous data on thin Mo film growth ( 6 3 ML) on rutile TiO2(1 1 0), and the structural evolution is discussed. � 2002 Published by Elsevier Science B.V.

Resonant spectroscopies offer a new opportunity to get more insight into excited electronic states by studying line shapes and intensities of decay processes. For photon excitations in the pre-K-edge region, the Ti KL 2,3 L 2,3 Auger spectra in TiO 2 show additional peaks when an electron is promoted in localized d-like states via a quadrupolar transition. This resonant process is used to unravel the respective contributions of quadrupolar and dipolar transitions to the absorption edge prepeaks.

TiO 2 thin films were deposited on (100) GaAs substrates by LP-MOCVD with deposition temperatures ( T d ) ranking from 450 to 750 °C. The structure of these layers was studied by X-ray diffraction (XRD) and Raman spectroscopy. The growth of the TiO 2 anatase phase was observed for T d T d >600 °C. Finally, X-ray photoelectron spectrometry (XPS) and secondary ion mass spectroscopy (SIMS) experiments showed the presence of small quantities of Ga and As through the whole film thickness, slightly increasing at the surface of the layers. This result was related to the SEM observations and explained by considering the growth conditions.

Dynamic segregation phenomena were revealed by XPS during the oxidation of some ferrites (Fe 2.5 Ti 0.5 O 4 , Fe 2.5 Ni 0.5 O 4 , Fe 2 CrO 4 and FeCr 2 O 4 ). This kind of phenomenon induces, at a low temperature (below room temperature), drastic changes in the cationic composition of the most external layers. Dynamic segregation is a function of the cationic composition, the oxidation capability and the morphology of these ferrites. Although dynamic segregation seems to be a quite frequent phenomenon that often can be observed during ferrite oxidation, there are materials in existence where it does not appear, such as molybdenum ferrite.

Multi-cationic spinel compounds are solids that exhibit polar faces. X-ray Photoelectron spectroscopy revealed the main phenomena allowing the stabilization of these faces, carried out as a function of the material treatment, particularly the cooling rate after thermal treatment at a high temperature (1200°C). This study showed that, whatever the cooling rate, each sample is subject to a significant hydroxylation that reduces the polarity. Nevertheless, it appears that the hydroxyl group content at the surface is a strong function of the cooling rate. Indeed, whereas quenched materials are subject to high levels of hydroxylation, slowly cooled samples are sparingly hydroxylated. This phenomenon corresponds to the fact that, during a slow cooling down, a change of the cationic composition in the topmost layers of the solids is able to occur, inducing a decrease of the polarity. Moreover, this segregation comes with a change of the grain surface morphology, leading to less polar faces. Copyright © 2002 John Wiley & Sons, Ltd.

Thin films of TiNxOy were deposited by d.c. magnetron sputtering on glass substrates using an (Ar+,N2) plasma and Ti target. The N2 partial pressure was changed from 2.3 × 10−4 mbar to 4.6 × 10−3 mbar in order to obtain films with increasing nitrogen contents. X-ray photoelectron spectroscopy was used to determine the as-deposited composition. The presence of oxygen, which is probably due to contamination from the residual atmosphere in the vacuum chamber, is always detected, both in the surface layers and in the bulk of the films, confirming the formation of TiNxOy. When the nitrogen partial pressure was increased, a maximum for the nitrogen content in the films was reached, corresponding to a TiN0.8O0.4 film composition. The nitrogen content of the films did not increase further for higher N2 partial pressures. X-ray diffraction showed that each deposited layer had a rock salt structure, isomorphic to that for TiN, in which some nitrogen atoms would seem to be substituted by oxygen atoms in the anionic sub-lattice. Moreover, this crystalline TiNxOy phase is super-stoichiometric with this deposition method. To the best of our knowledge such results have already been observed on TiN films but it is the first time that they have been presented for TiNxOy thin layers. Copyright © 2002 John Wiley & Sons, Ltd.

TiO2/TiNxOy superlattices were grown by Low Pressure-Metal-Organic Vapor Phase Epitaxy (LP-MOVPE) technique at deposition temperatures ranking from 650 to 750°C. The growth was performed on top of TiO2(110) rutile substrates. Intense peaks observed in the X-rays rocking curves and θ-2θ diffraction patterns show the presence of crystalline epilayers. The TiNxOy layers were grown in a (200) cubic structure on the (110) quadratic TiO2 epilayer structure. Transmission electron microscopy confirmed the XRD results and showed the formation of periodic and well structured epilayers.

Palladium and its alloys have been extensively studied because of their faculty to store reversibly hydrogen isotopes. Here, the substitution of palladium with platinum is investigated. Thermodynamical studies have shown an anomalous behaviour regarding to the classical models. This original behaviour is explained by the study of the electronic structure of the binary solid solutions. The drastic decrease of the hydrogen solubility in the Pd–Pt alloys is accounted for by the filling up of the palladium conduction band by the valence electrons of platinum. The anomalous decrease of the stability of the hydride is explained by the large broadening of the valence band due to the substitution.

The ratio of the two components of the L 23 M 23 V Auger transition is currently used to determine the stoichiometry of titanium oxides. The reduction of Ti manifests itself by a relative increase (decrease) in intensity of the Auger component lying at high (low) kinetic energy, which is assigned to an intraatomic (interatomic) transition involving Ti 3d (O 2p) valence electrons. The LMV Auger transition is herein revisited via its resonant behaviour at the Ti L 23 absorption edge in TiO 2 . Resonances of the high energy component occurs exclusively at the L 2 edge, while resonances of the other component are seen at the L 3 edge, but also at the L 2 edge. The latter being attributed to a L 2 L 3 V Coster–Kronig transition, the low- and high-lying LMV are identified as L 3 MV (including those following CK) and L 2 MV transitions, respectively, at variance with the previous assignment.

TiN(O)–TiO 2 thin films were prepared on Si(1 0 0) by the low pressure organo metallic chemical vapor deposition (LP-OMCVD) method, using ammonia and titanium isopropoxide as precursors. In order to complete previous characterizations, an Ar + bombardment/XPS coupled study was carried out. This method is based on the fact that the behavior of a compound towards an ion bombardment is a function of its composition. In particular, Ar + bombardment of TiO 2 (whatever its form) leads to a preferential sputtering of oxygen atoms with subsequent reduction of titanium and formation of Ti 3+ and Ti 2+ easily detectable by XPS from a significant broadening of the Ti 2p lines. In the opposite, no broadening of the Ti 2p lines is observed for an Ar + bombardment of TiN. Then, with this method, we succeed in showing that films obtained at high temperature (≥700°C) contain only a TiN x O y phase which is isomorphic to TiN. In the coatings, synthesized at low temperatures (≤650°C) amorphous TiO 2 has been evidenced.

TiNxOy/TiO2 multilayers have been grown by LP-MOCVD using titanium isopropoxide (TIP) precursor during the whole growth, but with an ammonia flow interrupted for the TiO2 layers. The one step growth process used to grow these structures allowed to stack the conducting and insulating layers without any growth breakdown. SIMS and TEM analyses showed the presence of an alternated insulating/conducting layers structure. Moreover, electrical measurements allowed to measure the dielectric part of insulating TiO2 stacked in these structures, whose permittivity was found to be about 80 for a MOS structure. Thus, such multilayers may lead to very promising applications in the microelectronics field.

Titanium oxinitride thin films have been grown by low pressure metal organic chemical vapor deposition (LP-MOCVD) using titanium isopropoxide, Ti(OCH(CH 3 ) 2 ) 4 (TIP) and NH 3 precursors in a growth temperature range from 450 to 750°C on sapphire substrates. The electrical behaviour of these films was studied between 400 and 173 K, revealing three different behaviours, ranking from a hopping conductivity (450–500°C) to a conducting one (700–750°C), with a dual behaviour for the intermediate growth temperatures. Moreover, at room temperature, both conductimetry and impedance spectroscopy highlighted a percolation behaviour, interpreted in terms of continuum percolation. The effective media theory equations led to the usual percolation parameters ( s , t , Φ c ) and the difference between the values thus obtained and the expected ones was explained in terms of anisotropic percolation occurring in the columnar film structure.

Exposures to oxygen at room temperature and annealings under vacuum were carried out on deposits obtained from molybdenum interacting with (1 1 0) TiO 2 surfaces in order to obtain molybdenum oxide ultra thin films. Exposures to oxygen at room temperature show that the interfacial molybdenum oxide layers resulting from the TiO 2 /Mo interactions are inactive towards oxygen whereas the metallic molybdenum clusters, which grew on top of the interfacial layers, oxidise into MoO 3 . Besides, during annealings under vacuum, substrate oxygen anions can diffuse into the deposit. Thus, between 400 and 500°C, molybdenum oxide layers are progressively oxidised into MoO 2 . Moreover, from the annealing temperature, it is possible to control the film oxidation and to select its stoichiometry. At higher temperatures, MoO 2 layers oxidise, leading to MoO 3 clusters which sublimate restoring a clean TiO 2 surface. As concerns the metallic clusters, if they are exposed to air and then oxidised in MoO 3 prior to annealing, they sublimate below 300°C.