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Oxygen reduction reaction (ORR) is a crucial process that drives the operation of several energy storage devices. ORR can proceed on the neat carbon surface in the absence of a catalyst, and its electrochemical activity is determined by its microstructure and chemical composition. Oxygen functional groups unavoidably existing on the carbon surface can serve as adsorption sites for ORR intermediates; the presence of some oxygen functionalities gives rise to an increase in the density of electronic states (DOS) at the Fermi level (FL). Both factors should have a positive impact on the electron transfer rate that was demonstrated for ORR in aqueous media. To study the O-groups effect on the aprotic ORR, which is now of interest due to the extensive development of aprotic metal-air batteries, we use model oxidized carbon electrodes (HOPG and single-layer graphene). We demonstrate that oxygen functionalities (epoxy, carbonyl, and lactone) do not affect the rate of one-electron oxygen reduction in aprotic media in the absence of metal cations since their introduction practically does not increase DOS at FL. However, in Li+-containing electrolytes, oxygen groups enhance both the rate of second electron transfer and carbon degradation due to its oxidation by LiO2 yielding carbonate species.

In order to study the performance, cycling stability and safety of electrochemical storage devices, various characterisation methods are applied. Magic angle spinning (MAS) NMR enables ex situ studies of electrochemical reactions with high resolution. In the present work, we follow the changes that occur in the MAS NMR spectra of lithiated graphitic materials after storage. The measuring time has been significantly shortened by using fine-grained graphitic material with 65% 13C-isotope enrichment. Our results show that for 13C graphitic electrode material with a low lithiation degree, visible changes in the 13C NMR spectra are observed already in few hours, whereas the samples with a higher lithiation degree demonstrated greater stability even after several days. We analyzed the deintercalation behavior in these materials using 7Li MAS NMR and oxidation processes using in situ X-ray photoelectron spectroscopy. During storage Li ions migrate to the other interlayers (redistribution), large pores and to the surface, where interaction with air takes place. Effects of charge transfer from Li to graphite across four graphitic layers guarantees that 13C NMR spectra are less affected by these effects. The key finding is that special care has to be paid to the ex situ characterisation of electrochemically prepared graphitized materials.

It was shown, that the treatment of graphite oxide (GO) at a temperature of 1000 °C and a static pressure of 500 bar recovers the graphene layers. Addition of triphenylphosphine to GO helps in removal of oxygen during the treatment and allows introducing ca. 0.7 at% of phosphorus in the product. Most phosphorus atoms are bonded with oxygen as the 31P nuclear magnetic resonance spectrum showed. An analysis of the X-ray photoelectron P 2p spectrum additionally found the components corresponding to C P and P P bonding. Assembling of phosphorus atoms into nanometer clusters was confirmed by transmission electron microscopy. Raman spectroscopy and electrical conductivity measurements revealed the n-type doping of graphitic material through the incorporation of phosphorus.

Titanium carbide attracts growing interest as a substrate for graphene growth and as a component of the composite carbon materials for supercapacitors, an electrode material for metal-air batteries. For all these applications, the surface chemistry of titanium carbide is highly relevant and being, however, insufficiently explored especially at atomic level is a subject of our studies. Applying X-ray photoelectron spectroscopy (XPS) to clean (111) and (755) surfaces of TiC, we were able to obtain the detailed spectroscopic pattern containing information on the plasmon structure, shake up satellite, the peak asymmetry and, finally, surface core level shift (SCLS) in C 1s spectra. The latter is essential for further precise studies of chemical reactions. Later on, we studied interface between TiC (111) and (755) and graphene and found the SCLS variation due to strong chemical interaction between graphene and substrate. This interaction is also reflected in the peculiar band structure of graphene probed by angle-resolved photoelectron spectroscopy (ARPES). Based on LEED data the structure is close to (7√3 × 7√3)R30°, with graphene being slightly corrugated. We found that similarly to the graphene on metals, the chemical interaction between graphene and TiC can be weakened by means of intercalation of oxygen atoms underneath graphene., We thank Helmholtz-Zentrum Berlin (HZB) for the allocation of synchrotron radiation beamtimes at the Russian-German and UE112-PGM2 beamlines. The work was financially supported by the Russian Science Foundation (project 16-42-01093). DFT calculations were performed at “Lomonosov” MSU supercomputer.

Efficient control over the grain boundaries (GBs) is a vital aspect in optimizing the graphene growth conditions. A number of methods for visualization of GBs were developed for graphene grown on weakly interacting surfaces. Here, we utilize oxygen intercalation to reveal GBs and study their morphology for graphene strongly bound to the cobalt surface. We demonstrate that upon the intercalation of oxygen, GBs in polycrystalline graphene become easily detectable due to graphene cracking and selective oxidation of the substrate, thus giving a direct insight into the graphene micro- and nanostructure by means of different electron microscopy methods, including scanning electron microscopy, photoemission microscopy and low-energy electron microscopy.

A new method for synthesis of graphene-protected iron silicides has been tested, which consists in formation of graphene on Ni(111) followed by two-step intercalation of the system with Fe and Si. Characterization of the samples was performed in situ by low-energy electron diffraction, angular-resolved photoelectron spectroscopy, core-level photoelectron spectroscopy with synchrotron radiation and magnetic linear dichroism in photoemission of Fe 3p electrons. It is shown, that at 400 °C the intercalation of graphene/Ni(111) with iron occurs in a range up to 14 ML. The graphene layer strongly interacts with the topmost Fe atoms and stabilizes the fcc structure of the film. The in-plane ferromagnetic ordering of the film has a threshold nature and arises after the intercalation of 5 ML Fe due to the thickness-driven spin reorientation transition. Subsequent intercalation of graphene/Fe/Ni(111) with Si leads to the formation of the inhomogeneous system consisted of intercalated and nonintercalated areas. The intercalated islands coalesce at 2 ML Si when a Fe-Si solid solution covered with the Fe3Si surface silicide is formed. The Fe3Si silicide is ferromagnetic and has an ordered (√3 × √3)R30° structure. The graphene layer is weakly electronically coupled to the silicide phase keeping its remarkable properties ready for use.

Three rectorite samples from the Beatrix Gold Mine, South Africa were characterized. Scanning electron microscopy revealed a layered morphology. High resolution transmission microscopy showed well distinguished light and dark layers of about 2.20 nm consistent with the 1:1 interstratified mica-smectite nature. X-ray diffraction measurements confirmed the basal spacing d001 of 2.20 nm consistent with a one-water-layer structure. Unit cell parameters, for a monoclinic unit cell with primitive lattice, refined to a = 5.177 A; b = 8.980 A; c = 22.489 A and β = 97.335° with mean crystallite size around 14 nm and calculated cell volume of 1045 A3. The Greene-Kelly test suggested that the expandable smectite layers have montmorillonite-beidellite composition. Nuclear magnetic resonance spectroscopy indicated a high degree of Al substitution and the presence of two different Al sites corresponding to six- and four-fold octahedral and tetrahedral aluminum respectively. The chemical composition and diffraction data suggest that the mica is Na-Ca-rich, i.e. of paragonite-margarite series. The fixed interlayer regions (mica interlayers) contains proportionally dominant Na+ and Ca2 + and minor amounts of K+. The exchangeable smectitic interlayers contain almost equal amounts of Na+ and Ca2 + ions. The distribution of the interlayer Na+ ions was quantified by 23Na solid-state NMR spectroscopy. It points to a three component mixed-layer structure with considerable variation in the composition of the mica layer of the different samples.

Ultrathin (∼2 nm) films of Co 2 FeSi ferromagnetic alloy were formed on silicon by solid-phase epitaxy and studied in situ . Experiments were carried out in an ultrahigh vacuum (UHV) using substrates of Si(1 1 1) single crystals covered with a 5 nm thick CaF 2 barrier layer. The elemental and phase composition as well as the magnetic properties of the synthesized films were analyzed by photoelectron spectroscopy using synchrotron radiation and by magnetic linear dichroism in photoemission of Fe 3 p and Co 3 p electrons. The study shows that the synthesis of the Co 2 FeSi ferromagnetic alloy occurs in the temperature range of 200–400 °C. At higher temperatures, the films become island-like and lose their ferromagnetic properties, as the CaF 2 barrier layer is unable to prevent a mass transfer between the film and the Si substrate, which violates the stoichiometry of the alloy.

We show that irradiation of room-temperature fluorinated graphite of C 2 F composition by electron beam with a kinetic energy of 500 eV detaches the fluorine atoms from two or three top layers. The dielectric property of C 2 F prevents effective penetration of the beam in depth of the sample, and electrons are accumulated between the interior layers. Comparative study of the initial C 2 F sample and that after irradiation by means of X-ray photoelectron, X-ray absorption near edge structure, Raman and reflection optical spectroscopy detects a partial recovering of the π-bonds which increases the surface conductivity by more than three orders. The mechanism responsible for removal of fluorine atoms from dielectric matrix under electron irradiation is proposed and substantiated by quantum chemical calculations.

Copper containing bismuth titanates with pyrochlore type structure were obtained by ceramic procedure over a wide range of compositions. The results of measurement of pycnometric density of the pyrochlores and of X-ray powder diffraction structure refinement point to the preference for copper atoms to occupy the Bi 3 + -sites. TGA study of a series of synthesized compounds indicates a reversible reduction of the copper (2) to copper (1). The NEXAFS Cu2p spectra of bismuth copper titanate pyrochlores point to copper being mainly in the oxidation state + 2 in these solid solutions. Electric properties were studied for single phase pyrochlores based on bismuth titanates. The results of investigations show the presence of oxygen ionic conductivity in these samples.

The recently discovered “rods-in-belt” supramolecular complexes with Au Cu or Au Ag cluster cores exhibit self-assembly behavior, have a very unusual structural motif, and what is most important, show remarkable light emitting properties. The electronic and photophysical characteristics of these unique objects can be relatively easy tuned by modifying the ligand (alkynyl and phosphine) environment. Because of these properties the “rods-in-belt” supramolecules could serve as building blocks for next generation electronics, and in particular, for light-emitting devices and in bioimaging applications. Herein, we report a comprehensive characterization of the electronic structure of two families of alkynyl-diphosphine supramolecular complexes with the heterometallic Au Cu and Au Ag cores. Using X-ray photoemission and absorption spectroscopy we disentangled the structure of their occupied and unoccupied electronic states close to the Fermi level. The results obtained suggest that the major contribution to the highest occupied molecular orbitals is made by the triple bonded carbons hosted in the dialkynyl-gold “rods” and the copper (silver) atoms from the central cluster core of the heterometallic Au Cu (Au Ag) molecules. The lowest unoccupied molecular orbitals are located on the carbon skeleton of the complexes and include π*-C C and π*-C C aromatic orbitals. The onset of the valence band in the Au Ag systems starts at about 0.3 eV lower than that in the Au Cu complexes, implying a slightly larger energy gap for the silver-based systems. It was also established that with increasing size of the complexes, the molecule becomes more and more sensitive to X-ray damage effects.

Manganese-containing bismuth titanate solid solutions with a pyrochlore-type crystal structure were obtained by the ceramic technique over a wide range of compositions. The NEXAFS (near-edge X-ray absorption fine structure) spectra of Mn2p-absorption in bismuth manganese titanate pyrochlores point to manganese being mainly in the oxidation state + 2 in these solid solutions. The Mn-rich bismuth titanate pyrochlores showed a superposition of antiferro- (long-order) and ferromagnetic (short-order) behavior. The results of impedance investigations show the electron–ionic conductivity in these samples.

Carbon-encapsulated iron carbide nanoparticles have been produced by co-carbonization of a mixture of an aromatic heavy oil and ferrocene at 450 °C under autogenous pressure. Transformations of the morphology and electronic structure of nanoparticles induced by air oxidation and subsequent heat treatment in a nitrogen atmosphere were examined using transmission electron microscopy, X-ray diffraction, near edge X-ray absorption fine structure spectroscopy, and X-ray emission spectroscopy. It was found that hollow nanoparticles, composed of iron oxides and oxidized carbon, were developed with thermal air oxidation of the initial product at 280 °C for 5 h. The mild oxidation of the product (250 °C for 3 h) followed by the carbonization at 500–550 °C yielded the hollow nanoparticles containing iron carbide/oxides and defective graphite-like carbon. The further annealing of nanoparticles at 1000 °C produced carbon nanocapsules with highly graphitized carbon walls and partially filled by spherical iron carbide nanoparticles.

Until now, there is a lack of knowledge about the presence of chitin in numerous representatives of corals (Cnidaria). However, investigations concerning the chitin-based skeletal organization in different coral taxa are significant from biochemical, structural, developmental, ecological and evolutionary points of view. In this paper, we present a thorough screening for the presence of chitin within the skeletal formations of a poorly investigated Mediterranean black coral, Parantipathes larix (Esper, 1792), as a typical representative of the Schizopathidae family. Using a wide array variety of techniques ( 13 C solid state NMR, Fourier transform infrared (FTIR), Raman, NEXAFS, Morgan-Elson assay and Calcofluor White Staining), we unambiguously show for the first time that chitin is an important component within the skeletal stalks as well as pinnules of this coral.

Proton dynamics in pristine and organically-modified layered double hydroxide has been studied by 1H T1ρ. Inverse Laplace transform with spectral resolution results in a correlation of T1ρ and chemical shift. In LDH two contributions are resolved. They are assigned to the metal hydroxides, forming the LDH sheets (4–8 ms), and mobile interlayer water (2 ms). Apparent T1ρ values of OH-protons in surfactant-modified LDH are different in dodecylbenzenesulfonate- (SDBS) and sodium octasulfonate- (C8) modified LDH. This difference is explained by the presence of water in LDH–SDBS. The effects of spin diffusion have been studied by performing 2D 1H RFDR in the LDH–SDBS.

In order to evaluate the biomedical potential of three-dimensional chitinous scaffolds of poriferan origin, chondrocyte culturing experiments were performed. It was shown for the first time that freshly isolated chondrocytes attached well to the chitin scaffold and synthesized an extracellular matrix similar to that found in other cartilage tissue engineering constructs. Chitin scaffolds also supported deposition of a proteoglycan-rich extracellular matrix of chondrocytes seeded bioconstructs in an in vivo environment. We suggest that chitin sponge scaffolds, apart from the demonstrated biomedical applications, are highly optimized structures for use as filtering systems, templates for biomineralization as well as metallization in order to produce catalysts.

Marine invertebrate organisms including sponges (Porifera) not only provide an abundant source of biologically active secondary metabolites but also inspire investigations to develop biomimetic composites, scaffolds and templates for practical use in materials science, biomedicine and tissue engineering. Here, we presented a detailed study of the structural and physico-chemical properties of three-dimensional skeletal scaffolds of the marine sponges Aiolochroia crassa, Aplysina aerophoba, A. cauliformis, A. cavernicola, and A. fulva (Verongida: Demospongiae). We show that these fibrous scaffolds have a multilayered design and are made of chitin. (13)C solid-state NMR spectroscopy, NEXAFS, and IR spectroscopy as well as chitinase digestion and test were applied in order to unequivocally prove the existence of alpha-chitin in all investigated species.

The evolution of electronic structure of the organic semiconductor iron-phthalocyanine with potassium doping has been studied by means of photoemission spectroscopy, near-edge X-ray absorption fine structure and density functional theory (DFT) calculations. The DFT study and detailed analysis of the core-level spectra permit us to suggest possible lattice sites for the potassium ions. The data disclosed filling of the lowest unoccupied molecular orbital upon doping and associated changes of the core level absorption spectra. None of the films prepared in our studies showed a finite electronic density of states at the Fermi level.

Localized Yb 4 f and itinerant Rh 4 d states are subject to substantial hybridization effects in the heavy-fermion material YbRh 2 Si 2 . The proximity to the Fermi level and the high anisotropy in k space naturally raise questions regarding the role of these hybridization effects for the observed, unusual physical properties. Using angle-resolved photoemission spectroscopy (ARPES) we found that the non-dispersive behavior of the localized Yb f states is broken around the Γ point due to interaction with approaching Rh 4 d bands. The intriguing point here is that the hybridization strength turns out to be systematically tunable by electron doping of the material. Gradual deposition of silver atoms onto the atomically clean, silicon terminated surface of YbRh 2 Si 2 leads to transfer of Ag 5 s charge into the Rh 4 d bands. This substantially changes the energy overlap, and thus the hybridization strength, between the interacting Yb 4 f and Rh 4 d bands in the surface and subsurface region. The shown possibility to control the variation of the f – d hybridization at the surface of heavy-fermion materials may also be helpful for other ARPES studies on the diverse phenomena in electron-correlated materials.

High-resolution core-level data from the prototypical In/Si(1 1 1) system have been acquired at 10 K. An asymmetric tail in the In 4d spectra reveals a metallic character of the low temperature Si(1 1 1)8 × 2 phase confined to the inner indium rows. The decoupling of the one-dimensional inner indium chains from any metallic environment at ∼10 K suggests a possible Luttinger liquid behavior. At room temperature essentially a broadening of the spectral features is noticed, which appears compatible with a fluctuation scenario.

In the present work we report on high-quality results of angle-resolved photoemission studies of thin Yb layers (1-3 ML thick) on a W(110) substrate. Growth of the thin Yb layers was monitored via permanent measurements of photoemission spectra during Yb deposition. This method allows to monitor the thickness of the deposited Yb with very high accuracy due to strong layer-dependent binding energy shifts of the Yb 4f emission. Contrasting to Ce/W(110) no hybridization of the 4f states with the own 6s-derived band is observed for the Yb layers. Instead, a splitting of the Yb 4f 7/2 emission is observed around the Γ-point that is due to interactions with the W 5d-derived substrate band and could quantitatively be described in the framework of the Periodic Anderson model.

The achievement of high hybridization efficiency in DNA microarrays is largely affected by the surface density of immobilized functional DNA probes. We investigated the chemical conditions for the formation of mixed self-assembled monolayers of thiol-modified oligonucleotides and mercaptohexanol deposited onto gold surfaces. The surface density of DNA was studied by means of high-resolution X-ray photoemission spectroscopy. The measurements revealed that the spatial density of DNA strands can be controlled within a wide range by the concentration of MgCl 2 in the immobilization buffer. Moreover, improved preparation conditions for high-quality self-assembled hybrid monolayers are presented. Compared to our previous work, a reduction in unbound thiol was achieved by changing from ethanolic to aqueous solvent and lowering the MCH concentration.

Photoemission spectra of solid fluorinated fullerenes C60Fx (x = 18, 36) were measured in comparison with parent C60 using synchrotron radiation (hν = 120 eV) providing the spectra in the density of states mode. Creation of the ion-like bonding of fluorine and disappearance of the π-states were observed to be a result of fluorination. Disappearance of the upper lying π-states was revealed to be a reason of the band gap widening upon fluorination.

Nitrogen-doped carbon (CNx) nanotubes have been synthesized by acetonitrile vapor decomposition over catalyst nanoparticles produced in the result of thermolysis of solid solutions of Fe and Ni bimaleates. X-ray photoelectron spectroscopy revealed the nitrogen content in CNx nanotubes grows from 0.4 to 1.2 at%, when Ni portion in catalyst increases. Nitrogen doping level of sample produced using bimaleates of Fe and Ni taken in a ratio of 7:3 is deviated from this dependence due to formation of two phases of metallic catalyst. N 1s-edge X-ray absorption spectra of samples showed three peaks, which by results of quantum-chemical calculation on nitrogen-containing carbon nanotube (CNT) model were assigned to pyridinic, graphitic, and molecular forms of nitrogen. Measurements of current–voltage characteristics of the samples found the electron emission threshold is reduced with amount of nitrogen incorporated into CNx nanotubes.

Mercaptohexanol (MCH) monolayers assembled on gold surfaces were investigated by means of high-resolution X-ray photoemission spectroscopy (XPS). The presence of three chemical states of sulfur was detected which exhibit different strength of interaction with the gold surface. Comparing the relative intensities of the corresponding subspectra allowed to estimate which fraction of the deposited MCH molecules is not bound to the metal surface via the thiol group, and thus, the characterization of the quality of the self-assembled monolayer (SAM). The number of sulfur atoms bound to the gold surface decreased when part of the the hydroxyl endgroup of the assembled MCH molecules is substituted by DNA duplexes. Long-term irradiation experiments on MCH layers revealed that soft X-ray radiation induces damage of the SAMs, accompanied with a preferential cleavage of both hydroxyl groups and hydrogen atoms from the alkane chains, leading in turn to a rearrangement of those MCH molecules which were not bound to the gold surface during the SAM preparation. The fraction of molecules which are bound to the metal via the thiol group, however, is practically not affected by the irradiation with soft X-rays.

The initial stages of iron silicide growth on the Si(1 0 0)2 · 1 surface during solid-phase synthesis were investigated by photoelectron spectroscopy using synchrotron radiation. The experiments were made on iron films of 1–50 monolayer (ML) thickness in the temperature range from room temperature to 750 � C. Our results support the existence of three stages in the Fe deposition on Si(1 0 0) at room temperature, which include formation of the Fe–Si solid solution, Fe3Si silicide and an iron film. The critical Fe dose necessary for the solid solution to be transformed to the silicide is found to be 5 ML. The solid-phase reaction was found to depend on the deposited metal dose. At 5 ML, the reaction begins at 60 � C, and the solid-phase synthesis leads to the formation of only metastable silicides (FeSi with the CsCl-type structure, c-FeSi2 and a-FeSi2). A specific feature of this process is Si segregation on the silicide films. At a thickness of 15 ML and more, we observed only stable phases, namely, Fe3Si, e-FeSi and b-FeSi2. � 2007 Elsevier B.V. All rights reserved.

The filled and unoccupied electronic states of the organic semiconductor copper-phthalocyanine (CuPc) have been determined by a combination of direct and resonant photoemission, near-edge X-ray absorption and first principles calculations. The experimentally obtained electronic states of CuPc are in very good agreement with results of ab initio density of states, allowing to derive detailed site specific information.

The effect of hole doping on the crystal and electronic structure of La1−xSrxCo1−yNbyO3 (y=0.0–0.25) at the x=0.0; 0.2; 0.5 has been studied by neutron diffraction and X-ray absorption spectroscopy at the Co K and L2,3-edges. The preliminary analysis of the Co K and L2,3-edges X-ray absorption near edge structure (XANES) in La1−xSrxCo1−yNbyO3 series suggests that upon niobium doping, an increase of the intermediate Co3+ spin state and a decrease of low spin Co4+ states contributions occur. The possible explanation of the observed changes of crystal and electronic structure in these cobaltites is discussed.

The electronic structure of onion-like carbon (OLC) consisted of quasi-spherical and polyhedral nanoparticles and produced as a result of nanodiamond annealing at 1800 K and 2140 K has been probed by soft X-ray emission and X-ray absorption spectroscopy. The enhanced density of states in the vicinity of the Fermi level was revealed for OLC prepared at moderate temperature. Ab initio calculation on carbon models showed the only unpaired electrons at the zigzag edges of graphitic fragments can provide localized states observed in the X-ray spectra. With the increase of the annealing temperature the defects, which likely constitute the boundaries of incompletely closed onion shells, are healing.

The interaction of cobalt atoms with an oxidized Si(1 0 0)2 × 1 surface was studied by photoelectron spectroscopy with synchrotron radiation at room and elevated temperatures. The SiO x layer grown in situ on the crystal surface was ∼0.3 nm thick, and the amount of deposited cobalt was varied within eight atomic layers. It was found that Co atoms could penetrate under the SiO x layer even at room temperature in the initial growth. As the Co amount increased, a ternary Co–O–Si phase was formed at the interface, followed by a Co–Si solid solution. Silicide synthesis associated with the decomposition of these phases started under the SiO x layer at ∼250 °C, producing cobalt disilicide with a stable CaF 2 -type of structure.

Photoemission experiments and theoretical calculations for the system Au-stepped W(1 1 2), have been done at submonolayer coverage region ranging from 0.1 to 0.9 monolayers, for different sample orientations relative to the photon polarization, i.e. parallel and perpendicular to the steps direction. Valence-band photoemission spectra of the Au/W(1 1 2) system demonstrate sharp angular dependent features at 4.5 and 0.3 eV binding energies when the photon polarization is parallel to the steps direction. Density functional theory calculations were performed for the Au/W(1 1 2) system with monolayer and half monolayer Au coverages in order to assign the origin of these features.

The investigation of interface in the Fe/Cr multilayer by total electron yield (TEY) is presented. Samples with different thickness of Fe on the top of Cr layer were prepared in situ. TEY measurements were performed using synchrotron radiation at Russian–German beamline (RGBL) (BESSY II). Partial pair correlation functions were determined as a result of the solution of the inverse ill-posed problem. Also, concentration distribution function of solid-state solutions in the interface was obtained using a new technique. The results obtained demonstrate the BCC solid-state solution with average concentration Fe50Cr50 for interface Fe/Cr.

Cobalt adsorption and condensation on the Si(1 0 0)2 × 1 surface as well as solid-phase reaction of CoSi 2 formation have been studied by high-resolution photoelectron spectroscopy with synchrotron radiation. We have measured the Si 2p and valence-band spectra after the Co deposition from a submonolayer coverage to 6 ML thickness and a subsequent annealing to 600 °C. Room temperature Co adsorption results in the loss of the initial surface reconstruction, and the chemisorbed Co atoms appear to be embedded into the upper layer of Si(1 0 0); however, no stable CoSi 2 was observed. With further metal deposition, a discontinuous solid solution Co Si film was formed and the dissolved Si concentration decreased with the distance from the crystal surface. The formation of cobalt disilicide was found to occur in the range of 250–400 °C.

High resolution Fe L-, Cu L-, S L-edge and O K-edge X-ray absorption near-edge structure (XANES) spectra of synthetic bornite and the samples oxidized in air and leached in a ferric chloride solution have been recorded and compared with the spectra of chalcopyrite. The pre-edge shoulder in the Cu L-edge spectrum of bornite and the strong leading peak in the spectrum of chalcopyrite were attributed to the electron transitions to the minor density of unoccupied Cu 3d states, and the post-edge features were related to the states of s- and p-type. The Fe L-edge XANES showed the presence of predominant Fe 2+ for chalcopyrite, and some quantity of Fe 2+ for bornite cannot be excluded despite XPS and Mossbauer spectroscopy had previously detected only Cu + and Fe 3+ species in both minerals. The Cu L- and S L-edge spectra of bornite considerably modify and become similar to those of chalcopyrite after the oxidative leaching that produces the heavily metal-depleted surface layers, and the Fe L-edge XANES shows only a slightly increased contribution of Fe 2+ . The multiparticle configurations involving Fe 2+ and Cu 2+ or holes at S atoms may play a role in the L-spectra.

4f photoemission spectra of TbRh reveal a broadening of the 8 S term of the 4f 7 final-state multiplet into a double peak while multiplet components at higher binding energies remain unaffected. As in case of Pr 5 Rh 4 and Nd 5 Rh 4 , where similar but larger splittings have been observed, the phenomenon is analyzed in the light of a single-impurity Anderson model. As a result of this analysis, the hybridization parameter is found to decrease monotonously by a factor of 1.5 in going from the Pr–Rh to the TbRh compound as expected from calculated f→d hopping matrix elements. Two percent admixture of divalent 4f 9 configurations to the trivalent Tb 4f 8 ground state are concluded.

XPS, Fe Lα,β and Cu Lα,β X-ray emission and Fe L-, Cu L-, S L-edge and O K-edge absorption spectroscopies, Mossbauer spectroscopy and cyclic voltammetry were applied to study reacted surface layers of natural chalcopyrite, CuFeS 2 . The surfaces became metal-depleted after the anodic oxidation in 1 M HCl and the leaching in 1 M H 2 SO 4 +0.2 M Fe 2 (SO 4 ) 3 or 1 M HCl+0.4 M FeCl 3 solutions, with the sulfur excess and iron/copper ratio been higher in the last instance, and were enriched in copper after the electrochemical reduction. The electronic structures of the metal-deficient layers up to several tenths of micrometer thick were similar to that of chalcopyrite, except that the density of the highest occupied states depended on sulfur anions formed (predominant S 3 -anions after the ferric sulfate treatment, S 4 -anions after the ferric chloride leaching or the potential sweep to 0.9 V, etc.). The layers created by the preliminary oxidation had only a small effect on the chalcopyrite voltammetry. We suggest a new reaction mechanism considering a role of the surface changes, including disordering and Anderson localization of the electronic states.

sp-Like quantum-well states (QWS) in thin monocrystalline bilayer films of Ag and Au on W(1 1 0) and of single Ag films were studied by angle-resolved photoemission. We find that the propagation of the electronic states in the bilayer films along [1 1 1] depends on the energy relative to the band edge of Au metal at the L point of the Brillouin zone. In particular, QWS with binding energies less than this band-edge energy (≅1.1 eV) are strongly confined to the Ag layer, while for higher binding energies the QWS extend across the whole bilayer film. This clearly demonstrates the weakness of the potential barrier at the Ag/Au interface in the context of QWS formation at energies where electronic states exist in both metals.

Excellent results were obtained during commissioning of the Russian–German Beamline at bending-magnet D16-1A of the electron-storage ring BESSY II. The beamline is based on a Petersen-type plane-grating monochromator covering the XUV and soft X-ray photon-energy range. Photoionization spectra taken from the 2,–13 resonance of doubly excited He reveal a resolving power of E=DED100,000 at hn=64.12 eV. To our knowledge, this represents the best energy resolution achieved up to now on a bending-magnet beamline in the grazing-incidence photon-energy range. We present results on photon flux and dimensions of the light spot at the sample position, and show representative photoionization spectra of several gases studied in the course of the characterization of the beamline at various photon energies. The high stability of the beamline is demonstrated by the first observation of the weak 4,� 24 resonance of doubly excited He, which had not been observed before. r 2003 Elsevier Science B.V. All rights reserved.