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The work is devoted to obtaining of transparent nanocomposite materials as low loss, highly thermally conductive materials for potential laser applications. We report Ho3+:Y2O3–MgO nanocomposite ceramics with excellent mechanical and optical properties by combining glycine-nitrate process and spark plasma sintering. Morphology, structural-phase state, infrared transmittance and luminescence depending on the holmium concentration (0–12 at.%) were studied for the first time. It was found that optical transmittance reaches 75%@6000 nm for 3 at.% Ho3+:Y2O3–MgO ceramics. The absorption cross-section at 1931 nm and the emission cross-section at 2118 nm were determined to be σabs = 0.51 × 10−20 cm2 and σem = 0.29 × 10−20 cm2, respectively. Based on the testing results of luminescent characteristics it was demonstrated that Ho3+:Y2O3–MgO nanocomposite is a promising material for high-power eye-safe lasers operating in the 2 μm wavelength range.

This article presents an investigation of the sensing properties of chemiresistors based on Cu2O/CuO core–shell nanowires containing p–p′ heterojunctions. The nanowires were synthesized by a conven...

PtCu bimetallic alloys are known to provide better activity than pure platinum in proton exchange membrane fuel cells. However, such catalysts undergo complex degradation processes during fuel cell operation, resulting in deterioration of their activity. By using in situ electrochemical (EC) atomic force microscopy combined with in situ EC infrared reflection absorption spectroscopy, we provide a comprehensive investigation of morphological and structural transformations of PtCu model thin film catalysts during accelerated degradation tests (ADTs). The ADTs consist of potentiodynamic cycling to three different upper potentials relevant for different modes of fuel cell operation. The results show that, depending on the upper potential limit, PtCu alloy electrocatalysts are subject to drastic changes in the surface composition, morphology, and structure.

The adsorption of adenine, one of the structural units of DNA and RNA, on nanostructured cerium oxide was studied using synchrotron radiation based techniques: photoelectron and X-ray absorption spectroscopies. Using a systematic approach, we studied this biomolecule’s bonding to the inorganic surface and examined the effects of different stoichiometry, morphology and composition of cerium oxide films, as well as two methods of molecular deposition (evaporation in vacuum and deposition from aqueous solution). The adenine molecule chemisorbs on the stoichiometric (IV) cerium oxide intact via nitrogen atoms, independent of the oxide morphology and deposition technique. Annealing of the adenine adlayer at 250 °C causes CeO2 surface partial reduction, along with the partial deprotonation of the nitrogen. The reaction of adenine with ex situ prepared CeO2 films (nanostructured compact and porous) activates Ce4+ cation reduction not only on the surface but also in the subsurface layers accompanied by water deso...

A new method based on transformation of magnetron sputtered platinum thin films into platinum nanostructures enclosed by high-index facets, using electrochemical potential cycling in a twin working electrode system is reported. The controllable formation of various Pt nanostructures, described in this paper, indicates that this method can be used to control a selective growth of high purity Pt nanostructures with specific shapes (facets or edges). The method opens up new possibilities for electrochemical preparation of nanostructured Pt catalysts at high yield.

Simultaneous mass production of high quality vertically oriented graphene nanostructures and doping them by using an inductively coupled plasma chemical vapor deposition (ICP CVD) is a technological problem because little is understood about their growth mechanism over enlarged surfaces. We introduce a new method that combines the ICP CVD with roll-to-roll technology to enable the in-situ preparation of vertically oriented graphene by using propane as a precursor gas and nitrogen or silicon as dopants. This new technology enables preparation of vertically oriented graphene with distinct morphology and composition on a moving copper foil substrate at a lower cost. The technological parameters such as deposition time (1&ndash, 30 min), gas partial pressure, composition of the gas mixture (propane, argon, nitrogen or silane), heating treatment (1&ndash, 60 min) and temperature (350&ndash, 500 &deg, C) were varied to reveal the nanostructure growth, the evolution of its morphology and heteroatom&rsquo, s intercalation by nitrogen or silicon. Unique nanostructures were examined by FE-SEM microscopy, Raman spectroscopy and energy dispersive X-Ray scattering techniques. The undoped and nitrogen- or silicon-doped nanostructures can be prepared with the full area coverage of the copper substrate on industrially manufactured surface defects. Longer deposition time (30 min, 450 &deg, C) causes carbon amorphization and an increased fraction of sp3-hybridized carbon, leading to enlargement of vertically oriented carbonaceous nanostructures and growth of pillars.

This study used non-reactive magnetron sputtered polycrystalline cerium oxide thin films as model substrates to mimic the surface morphology of cerium oxide nanoparticles. We investigated the interaction between dextran and polycrystalline cerium oxide surfaces by atomic force microscopy, X-ray photoelectron spectroscopy, and reflection-absorption infrared spectroscopy. A simplified sample preparation method probing solid-liquid interface was set up by conducting aqueous adsorption procedures in an argon-filled glove bag connected to an ultra-high vacuum chamber. We found that the adsorption of dextran from aqueous solution onto the polycrystalline cerium oxide surface leads to a mutual charge transfer between dextran and cerium ions, creating a surface accumulation of Ce3+. In the aqueous environment, dextran hydroxyl groups adsorbs on the polycrystalline cerium oxide surface competitively with the dissociated hydroxyl groups from water. By investigating glucose adsorbed onto polycrystalline ceria prepared by physical vapor deposition, we further confirmed the role of hydroxyl groups from polysaccharide during interaction with ceria. Thermal annealing of the dextran adsorbed polycrystalline cerium oxide surface results in desorption of weakly bonded dextran below 100 °C and decomposition of dextran above 100 °C.

Recently we have tested a magnetron sputtered Pt-Co catalyst in a hydrogen-fed proton exchange membrane fuel cell and showed its high catalytic activity for the oxygen reduction reaction. Here we present further investigation of the magnetron sputtered Pt-Co thin film catalyst by both experimental and theoretical methods. Scanning electron microscopy and transmission electron microscopy experiments confirmed the nanostructured character of the catalyst. The surface composition of as-deposited and annealed at 773 K Pt-Co films was investigated by surface analysis techniques, such as synchrotron radiation photoelectron spectroscopy and X-ray photoelectron spectroscopy. Modeling based on density functional theory showed that the surface of 6 nm large 1:1 Pt-Co nanoparticles is almost exclusively composed of Pt atoms (>90%) at typical operation conditions and the Co content does not exceed 20% at 773 K, in agreement with the experimental characterization of such films annealed in vacuum. According to experiment, the density of valence states of surface atoms in Pt-Co nanostructures is shifted by 0.3 eV to higher energies, which can be associated with their higher activity in the oxygen reduction reaction. The changes in electronic structure caused by alloying are also reflected in the measured Pt 4f, Co 3p and Co 2p photoelectron peak binding energies.

Due to promising catalytic properties of cerium oxide, such based materials have been recognized as a suitable candidate for catalysts at the anode side of fuel cells. In order to achieve the largest active surface area, a commercially available gas diffusion layer used as Pt-CeOx catalyst support has been enhanced by the application of a CNx interlayer. Herein, the surface morphology modification, into the form of individual needles, observed by Scanning Electron Microscopy and Transmission Electron Microscopy, is presented. Furthermore, spectroscopy techniques, namely X-ray Photoelectron Spectroscopy, Electron Energy Loss Spectroscopy, and Energy Dispersive X-ray Spectroscopy reveal important role of nitrogen incorporated in the CNx interlayer that enables formation of very porous surface structures. In addition, it is demonstrated that tuning of catalyst film morphology provides a viable strategy towards higher performance in the PEMFC tests, complemented by better corrosion resistance of CNx interlayers under the start-up conditions of fuel cells.

In this study, PtxNi100-x (0 ≤ x ≤ 100) alloy catalysts were prepared using magnetron co-sputtering in order to reveal the correlation between their composition and catalytic properties as a cathode in proton exchange membrane fuel cells (PEMFCs). Fine power adjustment on magnetrons allowed to deposit alloys with precise composition and at the same time with identical thickness of 10 nm and similar morphologies. The powerful surface characterization techniques such as atomic force microscopy (AFM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), X-ray reflectivity (XRR) and X-ray photoelectron spectroscopy (XPS) were applied to thoroughly investigate the catalytic layers. The desired composition of the films was confirmed by EDX and XRD results. All deposited layers showed similar morphologies with vertical and horizontal roughness of ~0.35 nm and ~6 nm, respectively. XRD confirmed the alloy nature of the films with one crystalline phase of the fcc PtNi. The PtxNi100-x alloys showed significant enhancement of specific power (SP) comparing to the pure Pt in PEMFC. Particularly, the Pt25Ni75 sample exhibited the highest SP of 24 kW/g(Pt). This catalyst showed a 2- and almost 10-fold improvement in SP with respect to the Pt film and commercial nanopowder Pt catalyst, respectively.

CO oxidation on platinum oxide deposited by magnetron sputtering on flat (Si) and highly porous (multi-walled carbon nanotubes, MWCNT) substrates were examined using X-ray photoelectron spectroscopy, scanning tunneling microscopy, temperature-programmed desorption and temperature-programmed reaction in both UHV and ambient pressure conditions. Platinum in the freshly deposited thin film is present entirely in the 4+ oxidation state. The intrinsic CO oxidation capability of such catalyst proved to be significantly higher under approx. 480 K than that of pure platinum, presumably due to the interplay between metallic and cationic platinum entities, and the reaction yield can be further enhanced by increasing effective surface area when MWCNT is used as a support. The thermo-chemical stability of the platinum oxide, however, has its limitations as the thin film can be gradually thermally reduced to metallic platinum (with small residuum of stable Pt2+ species) and this process is further facilitated in the presence of reducing CO atmosphere.

In the present work, we have studied the interaction of palladium adsorbed on SnO2 (110) surfaces, considering the possible formation of clusters on the surface using density functional theory (DFT) calculations. We report structure, adsorption, and bonding properties of Pdn (n = 1–5) on stoichiometric and reduced SnO2 (110) surfaces. Although palladium can be adsorbed as metal clusters on both types of surfaces, these clusters can be more easily decomposed into Pd atoms on the reduced SnO2 surface. Pd interacts mainly with bridging O atoms on stoichiometric surfaces while it bonds strongly with Sn on the reduced surface. Fil: Robina, A.. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ingeniería - Sede Comodoro; Argentina. Universidad Nacional del Sur; Argentina Fil: German, Estefania. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina Fil: Pronsato, Maria Estela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina Fil: Juan, Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina Fil: Matolinová, I.. Charles University in Prague; República Checa Fil: Matolín, V.. Charles University in Prague; República Checa

Investigation of cerium oxide thin film deposition on silicon and silicon oxide is important due to many possible applications of cerium oxide based micro-systems in electronics and catalysis. rf-Magnetron sputtering is technologically the most suitable method of preparation of such systems. Mechanism of film growth is strongly influenced by interaction of Ce atoms with the substrate and their oxidation by oxygen containing rf plasma. We show using hard X-ray photoelectron spectroscopy with high information depth that cerium is reducing silicon oxide by forming complex silicate phase at the interface with Ce in the 3+ state. For this reason composition of very thin films of cerium oxide is strongly influenced by thin film–substrate interaction. A coating of the silicon oxide substrate by an intermediate thin carbon film provides conductive substrate for electrocatalytic applications and decreases the silicon oxide substrates–cerium oxide interaction essentially.

Changes of stoichiometry in reducible oxides are inevitably accompanied by changes of the oxide structure. We study the relationship between the stoichiometry and the structure in thin epitaxial fi...

Radio Frequency Magnetron Sputtering is used to elaborate CeO x layers doped with platinum and/or tin on a SiO 2 /Si substrate. Morphology, chemical composition and crystallographic structures were investigated by Transmission Electron Microscopy. The presence of nanoparticles of mainly ceria and metallic platinum is exhibited.

Nanocomposite metal/plasma polymer films have been prepared by simultaneous plasma polymerization using a mixture of Ar/n-hexane and metal cluster beams. A simple compact cluster gas aggregation source is described and characterized with emphasis on the determination of the amount of charged clusters and their size distribution. It is shown that the fraction of neutral, positively and negatively charged nanoclusters leaving the gas aggregation source is largely influenced by used operational conditions. In addition, it is demonstrated that a large portion of Ag clusters is positively charged, especially when higher currents are used for their production. Deposition of nanocomposite Ag/C:H plasma polymer films is described in detail by means of cluster gas aggregation source. Basic characterization of the films is performed using transmission electron microscopy, ultraviolet–visible and Fourier-transform infrared spectroscopies. It is shown that the morphology, structure and optical properties of such prepared nanocomposites differ significantly from the ones fabricated by means of magnetron sputtering of Ag target in Ar/n-hexane mixture.

The interaction of Pt with CeO2 layers was investigated by using high resolution hard X-ray photoelectron spectroscopy. Pt doped CeO2 layers were deposited simultaneously by rf-magnetron sputtering on a SiO2/Si substrate and carbon nanotubes (CNTs) grown on a carbon diffusion layer of a polymer membrane fuel cell. In the case of the CNT support photoelectron spectra showed the formation of ionic platinum rich cerium oxide with Pt2+,4+ species, and with the Pt2+/Pt4+ ratio strongly dependent on the amount of platinum. Ce reveals 4+/3+ mixed valent character with Ce3+ concentration increasing with Pt content. In the case of the SiO2/Si substrate the film revealed Ce4+ and Pt4+ species only.

The RF magnetron sputtering of polytetrafluoroethylene target is studied with the aim to find out conditions leading to the deposition of super-hydrophobic thin films. It is shown that such coatings can be prepared at elevated pressures and a longer distance between the sputtered target and the substrate. This is explained by an increase in the density of longer C x F y molecules that reach the substrate and a lower flux of ions and CF 2 radicals on the surface of growing film under such deposition conditions, as observed by optical emission spectroscopy and mass spectrometry. Such changes in plasma composition result in a deposition of rough films having F / C ratio close to 2 as observed by scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. These findings clearly distinguish our results from the previous investigations of polytetrafluoroethylene sputtering performed at shorter distances from the target, where either low F / C ratio or low roughness of the deposited films did not allow reaching super-hydrophobic character of the coatings.

Adjustable morphology and degree of reduction represent desirable properties of model oxide substrates for heterogeneous catalysis. We investigate these properties in CeO2 (ceria) thin films on Cu(111) using scanning tunneling microscopy and photoelectron spectroscopy. We identify growth mechanisms of ceria on Cu(111): formation of incomplete oxide interfacial layer and formation of three-dimensional ceria pyramids by stacking of monolayer-high islands. Using these mechanisms, we control the coverage, the number of open monolayers, and the step density of ceria thin films on Cu(111). Annealing in vacuum allows us to control besides the morphology also the degree of ceria surface reduction. We find a correlation between surface reduction and morphological stability in annealed ceria layers. Oriented and stoichiometric thin films of ceria on Cu(111) can be prepared at temperatures as low as 150 and 250 °C. Both the morphology and the surface reduction of these films readily change with increasing temperatur...

The interaction of Pt with CeO 2 in Pt-doped cerium oxide layers deposited on a Si wafer at normal and grazing incidence, and on multiwall carbon nanotubes (MWCNTs), was investigated by using X-ray photoelectron spectroscopy (XPS). 30-nm-thick Pt-doped CeO 2 layers were deposited by rf-magnetron sputtering of a composite CeO 2 -Pt target. XPS showed formation of cerium oxide with completely ionized species Pt 2+,4+ embedded in the film. The Pt 2+ /Pt 4+ ratio depends on the deposition angle and increases in the case of the film deposition on the MWCNTs. This behavior was explained by the dependence of the poiycrystalline film grain morphology on a deposition angle.

The photoelectron spectroscopy (PES) study compares electronic states in three different ceria thin film surfaces prepared on a Cu(111) single-crystal surface by vapour deposition under different conditions: at 250 °C, at room temperature and finally Au-doped ceria film obtained by simultaneous deposition of Au and CeO 2 at room temperature (RT). Electronic properties of the layers and interaction of gold with CeO 2 were investigated using synchrotron-radiation-excited PES and resonant photoemission (Ce 4d → 4f transitions). We observed partial Ce 4+ → Ce 3+ reduction induced by the decrease of deposition temperature to RT instead of 250 °C and also by doping ceria with gold, accompanied by a 4f resonance enhancement of the Ce 3+ species. In the case of the Au-doped sample the surface reduction degree is stronger and can be explained by the possible creation of a new ionic Au + state observed in the Au 4f spectra.

Cerium oxide films equivalent to 2 ML of CeO2 were grown at 520 K in an oxygen atmosphere on a clean Cu(111) substrate in order to prepare a model catalytic system. This “inverse model catalyst” was characterized by low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS) of core levels, and resonant photoelectron spectroscopy (RPES) of the valence band. Samples annealed at 770 K exhibited a LEED pattern corresponding to the (1.5 × 1.5) CeO2(111)/Cu(111) structure that can be interpreted as formation of a flat, well-ordered cerium oxide overlayer aligned with the principal crystallographic axes of the substrate. The model catalytic system corresponds well to a copper-loaded ceria nanopowder catalyst that exhibits growth of Cu(111) film structure on CeO2(111) planes. Lowering of the CO oxidation temperature due to the Cu loading is explained by CO adsorption on copper in the vicinity of highly active ceria planes providing oxygen for the reaction.

Photoelectron spectroscopy at different photon energies was used to optimize the photoexcitation cross section for valence band study of diamond-like hydrogenated carbon films. The electronic states of diamond-like carbon (DLC) were studied by synchrotron radiation photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. The valence band spectra measured at different excitation energies show the gradual emergence of the p–π band in relation to the sample annealing and ion bombardment amorphization. The p–π band of the annealed DLC was characterized by localized pz states whilst the formation of the amorphous carbon surface was accompanied by appearance of the delocalized pz states in the gap. Secondary ion mass spectrometry and thermal desorption spectroscopy showed that sample annealing was accompanied by hydrogen content decrease.

We have studied Pd–Sn layers with different composition prepared by magnetron sputtering. Layers were sputtered onto Al 2 O 3 and SiO 2 substrates and studied by X-ray photoelectron spectroscopy (XPS). Spectra confirmed that after vacuum annealing residual oxygen and carbon have been removed and bimetallic bonds have been created. The shift of Pd 3d 5/2 core level to higher binding energy followed by the peak narrowing in dependence on the composition was observed, accompanied by the shift of the Pd 4d in the valence band region, induced by hybridization of Pd-d and Sn-s,p states. Experiments carried out on a gas-flow reactor indicate increasing temperature of the CO oxidation with tin ratio in the alloy.

The Au/Ti(0 0 0 1) adsorption system was studied by low energy electron diffraction (LEED) and photoemission spectroscopy with synchrotron radiation after step-wise Au evaporation onto the Ti(0 0 0 1) surface. For adsorption of Au at 300 K, no additional superstructures were observed and the (1 × 1) pattern of the clean surface simply became diffuse. Annealing of gold layers more than 1 ML thick resulted in the formation of an ordered Au–Ti surface alloy. Depending on the temperature and annealing time, three surface reconstructions were observed by LEED: (√3 × √3) R30°, (2 × 2) and a one-dimensional incommensurate (√3 × √3) rectangular pattern. The Au 4f core level and valence band photoemission spectra provided evidence of a strong chemical interaction between gold and titanium. The data indicated formation of an intermetallic interface and associated valence orbital hybridization, together with diffusion of gold into the bulk. Au core-level shifts were found to be dependent on the surface alloy stoichiometry.

In this work, properties of non-evaporable getter (NEG) films prepared on stainless steel substrates by magnetron sputtering were investigated. Changes of the sample surface during thermal activation were studied by means of secondary ion mass spectroscopy (SIMS). Static SIMS observation of a superficial layer as well as dynamic profiling of the surface region were performed. Two samples of the same Ti:Zr:V stoichiometry were investigated following two different procedures of thermal activation. Step-by-step heating up to 320 °C (as model activation) and direct long time heating to 240 °C (continuous thermal activation) were applied. The SSIMS measurements are highly surface sensitive and reflect changes of the superficial oxide layer covering air-exposed surfaces during activation. To compare the final states of activation, depth profiles of surface layers have been used as well. Molecular ion intensity ratios MX + /M + (X=O, H; M=Ti, Zr, V) have been considered to be directly coverage-sensitive and were monitored during the processes. The results were checked by comparison to corresponding XPS experiments.

Carbon monoxide (CO) adsorption properties of Pd/Al systems have been studied using X-ray photoelectron spectroscopy (XPS), thermal desorption spectroscopy (TDS) and static secondary ion mass spectroscopy (SSIMS) under UHV conditions. Measured XPS and TDS spectra were compared to that of clean bulk metals (Pd, Al). Pd adlayers, prepared by vacuum evaporation onto a pure polycrystalline Al surface, exhibited a strong interaction with Al atoms resulting in formation of a Pd–Al alloy of a noble metal-like electronic structure. The shifts of the Pd 3d core levels and the Pd 4d-band centroid toward higher binding energies due to bimetallic bond formation were observed. The CO TDS spectra consisted of two desorption peaks, both lying lower than the one typical for a Pd foil, indicating distinct weakening of the Pd–CO chemisorption bond. Partial CO dissociation on the Pd/Al surface during adsorption/desorption cycles, accompanied by CO 2 and H 2 O production, was observed. CO dissociation caused creation of Pd–C and Al–O chemical bonds on the Pd/Al surface resulted in weakening of the Pd–Al bimetallic bond.

Zr–V alloy getter films were prepared on stainless steel substrates by magnetron sputtering. The thermal activation behavior of these getters was investigated by synchrotron radiation photoelectron spectroscopy using photon excitation energies of 600, 250 and 73 eV. Depth resolved results were compared to the results of the SIMS profiling. The measurements confirmed the disappearance of the superficial oxide layer covering the air-exposed Zr–V surfaces via its progressive reduction during the thermal activation. The depth sensitive results showed that the activated getter surface is covered by a residual zirconium sub-oxide.

In this work the study of a redox process on Pd/SnOx system by means of X-ray photoelectron spectroscopy (XPS) and static secondary ion mass spectrometry (SSIMS) is presented. SnOx substrates were prepared by spray pyrolysis onto Si(1 1 1). Palladium ultra-thin films were evaporated in UHV chamber and then stabilised in air at 720 K for 2 h. Results obtained after thermal treatment in 1% H2 containing air and in pure air showed the reversible change in palladium chemical state.

SnO 2 system is known to be very universal in gas sensing applications. Sensing properties can be improved by adding of a small amount of transition metals. The exact mechanism of this enhancement is not known yet. In this work we used X-ray photoelectron spectroscopy to study the chemical state changes during heating in usual and hydrogen containing atmosphere on Pd-doped SnO 2 powder prepared by microwave irradiation wet method. Reversible oxidation and reduction of Pd additive during the treatment were observed. We found out a dependence of the redox process on heating temperature and gas mixture proportion.

Polycrystalline Ni 3 Al alloy surface was investigated during CO adsorption–desorption experiments by means of X-ray photoelectron spectroscopy (XPS), low energy ion scattering (LEIS) and temperature programmed desorption (TPD). It was shown that CO partially dissociates giving nickel bonded carbon and carbon monoxide species and aluminum bonded oxygen. Thermal desorption was characterized by both low temperature CO desorption peaks typical for Ni–Al alloy, and high temperature one of highly reactive sites with lower CO dissociative barrier.

The metal–substrate and metal–metal interactions (MSI, MMI) represent important effects which can determine properties of supported catalysts. We investigated Pd–Al bimetallic interactions of Pd thin films vapor deposited onto non-stoichiometric aluminum oxide surfaces by means of X-ray photoelectron spectroscopy (XPS) and low energy ion scattering (LEIS). The formation of a Pd–Al surface alloy phase exhibiting noble metal-like electronic structure was observed. Changes of the Pd 3d and Pd 4d photoemission features and a modification of surface stoichiometry as a function of degree of aluminum surface oxidation as well as during CO adsorption–desorption cycles are discussed.

Thin films of the Zr–V getter alloy were prepared on stainless steel substrates using magnetron sputtering. The getter surface chemical composition was investigated by X-ray photoelectron spectroscopy (XPS) for four air exposure/activation cycles. The experimental results show the decrease of the activation capacity after several oxidation/activation cycles. The adsorbed carbon is transformed simultaneously to zirconium and vanadium carbides, which are inactive for both oxidation and reduction processes. Higher affinity of V to carbon atoms was confirmed by secondary ion mass spectroscopy (SIMS) study of CO adsorption.

The activated ZrV non-evaporable getter (NEG) film has been studied by means of X-ray photoelectron spectroscopy, low-energy ion scattering and secondary ion mass spectrometry. In this work, we found that the first atomic layer of the thermally activated ZrV NEG consists mainly of zirconium atoms, which are partly oxidized. The residual zirconium suboxides observed on thermally activated ZrV NEG diminish during ion sputtering of NEG surface. It indicates that residual suboxides are located mainly in the top surface layer.

Pd x Co 1− x thin layers with different stoichiometry, prepared by DC magnetron sputtering on α -Al 2 O 3 (sapphire) substrates, were investigated by X-ray photoelectron spectroscopy (XPS), static secondary ion mass spectroscopy (SSIMS) and temperature programmed desorption (TPD). The shifts of Pd 3d, XPS Auger Pd-MNN and the valence-band centre toward higher binding energies due to the formation of a bimetallic bond were observed. CO adsorption properties of the alloys were strongly dependent on alloy stoichiometry. The common property was the lowering of the CO desorption temperature with respect to the desorption from pure metals. The SSIMS study showed that CO partially dissociated on Co–Pd alloy surfaces.

In2O3 belongs to the group of metal oxides used successfully for gas detection, with sensitivity for CO and H2 comparable with that of SnO2 and excellent for O3. The sensing properties of these sensors could be greatly improved by adding small amount of transition metals such as Pd, Pt, Au, etc. In this work, we used X-ray photoelectron spectroscopy (XPS) and ion scattering spectroscopy (ISS) to study the growth of Pd particles on In2O3 substrates prepared by spray pyrolysis method. Surface stoichiometry and its changes during Ar+ ion bombardment used for surface cleaning were checked with XPS and ISS. The Pd growth was studied stepwise in situ using the micro-electron beam evaporation source (MEBES) with controlled evaporation rate. XPS and ISS measurements were carried out with special attention to metal–substrate interaction (MSI), which was observed for Pd–In and resulted in the formation of Pd–In alloy with noble metal-like electronic structure. Further, we studied reduction of these samples after oxidation in air. A lower reduction temperature than with bulk PdO was observed. The results are compared with the experiment of Pd deposition performed on a pure In foil.

The reactive vacuum deposition of CeO 2 on Cu(1 1 1) surface in oxygen atmosphere provides high quality epitaxial ceria overlayers. We report the growth characteristics of Ce oxide, the structures, and the temperature stability of the oxide phases as investigated by low-energy electron diffraction (LEED) and X-ray photoelectron spectroscopy. We find that Ce oxide on the Cu(1 1 1) grows initially in the form of islands giving sharp hexagonal LEED pattern of the CeO 2 (1 1 1) structure corresponding to the (1.5 × 1.5) structure. The CeO 2 –Cu(1 1 1) films exhibited mixed valence states and temperature dependent CeO 2 –Ce 2 O 3 transition above 900 K due to the vacuum annealing. The transition progressed more rapidly at the surface, probably by formation of oxygen vacancies.

Stoichiometric and partially reduced ceria films were deposited on preoxidized Ru(0001) crystal by Ce evaporation in oxygen atmosphere of different pressures at 700 K. Copper-ceria interaction was investigated by deposition of metalic copper on both types of substrate. The samples were characterized by low energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS) of core states and resonant photoelectron spectroscopy (RPES) of the valence bands. Copper adsorption on stoichiometric ceria caused reduction of CeO2, while on the oxygen-defficient ceria it partially reoxidized the substrate. This is in agreement with DFT+U calculations of copper adsorption on stoichiometric and defective ceria surfaces. (C) 2012 Elsevier B. V. All rights reserved.

The interaction of gold with CeO2 layers was investigated using photoelectron spectroscopy. 65 nm thick Au doped CeO2 layers were deposited by rf-magnetron sputtering on a Si(0 0 1) substrate by using a composite CeO2–Au target. The laboratory XPS and synchrotron radiation soft x-ray and hard x-ray photoemission spectra showed the formation of stoichiometric Ce4+ (CeO2) and the appearance of new Au+,3+ states with ionized Au species in excess of 50% of the total Au amount. Depth resolved measurements, by varying the emission angle or photon energy, indicated the formation of an Au0 overlayer and deeper Au+,3+ species. The formation of Au+,3+ ions was found to be strongly dependent on the cerium oxide stoichiometry. The amount of ionized Au can be reversibly decreased and increased by surface reduction (removal of O by sputtering) and subsequent surface re-oxidation.

The interaction of Pt with CeO 2 layers was investigated using photoelectron spectroscopy. Pt-doped CeO 2 layers 30 nm thick were deposited by radio-frequency (rf) magnetron sputtering using a composite CeO 2 -Pt target on a carbon diffusion layer of micropolymer membrane fuel cell covered by double-wall carbon nanotubes. The laboratory X-ray photoelectron spectroscopy and synchrotron radiation soft X-ray photoemission spectra showed the formation of cerium oxide with completely ionized species Pt 2+,4+ embedded in the film. A small amount of Pt 0 is present on the film surface only. Hydrogen/air fuel cell activity measurements normalized to the amount of used Pt revealed specific power up to 30 W/mg(Pt). The activity of this material is explained by high activity of embedded Pt 2+,4+ cations toward H 2 dissociation and formation of protonic hydrogen. Very high specific power and low cost together with planar deposition techniques make the material promising for microfabrication of fuel cells to power mobile systems.