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We have tried to generate x-ray beam carrying orbital angular momentum (vortex beam) at BL-16A in Photon Factory. The beam profile of 2nd harmonic radiation from helical undulator was measured, and that was explained by the calculated one of the vortex beam. Hence, it is expected to succeed in generating the vortex beam. We also elucidated that the simulated diffraction pattern with vortex beam is distinct from that with usual coherent beam. Hence the diffraction is an appropriate technique to evaluate the orbital angular momentum of x-ray beam. However, the orbital angular momentum could not be detected in this diffraction experiment.

Recent development of the depth-resolved X-ray absorption fine structure (XAFS) and X-ray magnetic circular dichro-ism (XMCD) techniques in the soft X-ray region is presented. A sub-nanometer resolution in the XAFS XMCD measurement is achieved by collecting the Auger electrons at di erent detection angles, which correspond to di erent probing depths, but it is impossible to apply this technique under magnetic and or electric fields because the electron trajectory is a ected by the external fields. By adopting the fluorescence-yield detection mode using a soft X-ray CCD camera, the depth-resolved XAFS XMCD tech-nique under the external fields is realized, which leads to the operando measurements for the chemical and magnetic states at the surface and interface. The depth-resolved XAFS XMCD measurement for an FeCo film under the magnetic field is demonstrated for the first time, which suggests that the ∼15 ML-thick surface region consists of ∼60% oxides with little magnetization.

Palladium atoms deposited by vapor deposition on a template of n-alkane molecules on a Au(111) surface exhibit strongly anisotropic growth. In the initial stage, a Pd nanorod is grown with its length regulated by the chain length of the template molecule. Nanorod formation and subsequent anisotropic cluster growth are induced by interactions between the Pd atoms and unsaturated bonds created by the dehydrogenation of the n-alkane. Dehydrogenation is catalyzed by the deposited Pd atoms, which produce Pd trap sites. Dehydrogenation is confirmed by the change in the X-ray absorption fine structure spectra at the near carbon K-edge (C K-NEXAFS). The electronic states of the Pd clusters are considerably confined, which show d-band narrowing as observed in the Pd L3-NEXAFS spectra.

X-ray photoelectron spectroscopy (XPS) is useful for in situ analysis of catalytically active surfaces under reaction conditions. We conducted in situ observations of CO oxidation on Pd single-crystal surfaces with different orientations under near ambient pressure (NAP) conditions with XPS. In this short review we compare catalytically active surfaces of Pd with the different orientations. Both surface oxides and atomic oxygen chemisorbed on metallic surfaces can be active for CO oxidation depending on surface geometric structure. We propose similarity between the surface oxides and the chemisorbed oxygen from a viewpoint of availability of active oxygen. Catalytic activity of the metallic surface under NAP condition is also compared with that under ultrahigh vacuum conditions.

The adsorption and reaction of CO and NO on Ir(111) have been studied by near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) together with low-energy electron diffraction, scanning tunneling microscopy, and mass spectroscopy (MS). Under both ultrahigh vacuum (UHV) and NAP conditions CO molecules occupy on-top sites of the Ir(111) surface at room temperature (RT) by forming two-dimensional clusters. Exposure to NO under UHV conditions at RT induces partially dissociative adsorption, while NAP NO exposure leads to a Ir(111) surface that is covered by molecular NO. We conducted in-operando NAP-XPS/MS observation of the NO + 13CO reaction under a NAP condition as a function of temperature. Below 210 °C adsorption of NO is inhibited by CO, while above 210 °C the CO inhibition is released due to partial desorption of CO and dissociative adsorption of NO starts to occur leading to associative formation of N2. Under the most active condition studied here the Ir surface is covered by a dense co-adsorption layer consisting of on-top CO, atomic N and O, which suggests that this reaction is not a NO-dissociation-limited process but a N2/CO2 formation-limited process.

The interaction between carbon monoxide (CO) and a Pd70Au30(111) alloy surface was investigated under CO pressures with a wide range from ultrahigh vacuum (UHV) to sub-Torr at room temperature by a combination of near-ambient pressure (NAP) X-ray photoelectron spectroscopy and density functional theory calculations. The adsorption site and surface coverage of CO are reversibly controlled by the CO pressure. Under UHV conditions, the CO molecules occupy bridge and hollow sites on contiguous Pd clusters in the Au-rich surface layer. Exposure to sub-Torr CO gas induces site switching of the adsorbed CO on the contiguous Pd clusters from multiple-coordination (hollow and bridge) sites to single-coordination (top) sites, even though the latter sites are energetically less favorable. This behavior is explained by a pressure-induced entropic effect on gas-phase CO, which is in equilibrium with the adsorbed CO. This site switching highlights an important aspect of high-pressure-induced adsorption behavior.

Surface ferromagnetic state of FeRh thin films irradiated with 1 keV Ar ion-beam has been investigated by using soft X-ray Magnetic Circular Dichroism (XMCD). It was revealed that the Fe atoms of the samples were strongly spin-polarized after Ar ion-beam irradiation. Due to its small penetration depth, 1 keV Ar ion-beam irradiation can modify the magnetic state at subsurface of the samples. In accordance with the XMCD sum rule analysis, the main component of the irradiation induced ferromagnetism at the FeRh film surface was to be effective spin magnetic moment, and not to be orbital moment. We also confirmed that the surface ferromagnetic state could be produced by thermal annealing of the excessively ion irradiated paramagnetic subsurface of the FeRh thin films. This novel magnetic modification technique by using ion irradiation and subsequent annealing can be a potential tool to control the surface magnetic state of FeRh thin films.

A one-shot recording technique for spatially-resolved X-ray absorption spectroscopy has been developed by combining wavelength-dispersed soft X-rays with a photoelectron emission microscope. The wavelength-dispersed soft X-rays, whose wavelength depends on the position, illuminate the sample, and a two-dimensional image of emitted electrons is obtained. Therefore, one can obtain spatial and spectroscopic information simultaneously, without scanning the monochromator. The technique opens the route to quantitative investigation for inhomogeneous and irreversible surface chemical reactions.

We develop bond-length mapping technique without two-dimensional scanning by combining photoelectron emission microscopy with extended x-ray absorption fine structure (EXAFS) analysis. Several tens of thousands of EXAFS data are simultaneously acquired, which corresponds to a data acquisition time less than 1 second per spectrum. We apply this technique to an Fe/BaTiO3 thin film, and two-dimensional distribution of the Fe-Fe bond length at the Fe surface is observed. From the Fe K-edge EXAFS analysis, we find that the Fe-Fe bond length is 2.52 A over the whole area with a Gaussian distribution of 0.01 A, which implies that this technique realizes a bond-length mapping with precise bond-length determination.

Ferrimagnets close to the magnetic compensation are excellent candidates to spin-torque-based spintronic applications, as their small magnetizations allow lowering switching currents. Here, we studied the magnetic compensation of Mn4 − xNixN epitaxial films by performing x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) measurements at the L2,3 absorption edges of Mn and Ni atoms and compared them with those of Ni3FeN films. The XAS spectrum of the Ni3FeN films exhibits shoulders at approximately 2 eV above the Ni L2,3 main peaks, originating from orbitals hybridization between Ni 3d at face-centered (II) sites and N 2p at body-centered sites. However, such shoulders are not observed at the Ni L2,3 edges of the Mn4 − xNixN films (x = 0.1 and 0.25). These results indicate that the orbitals of Ni atoms do not hybridize with those of N atoms. Hence, Ni atoms preferentially occupy corner (I) sites, where hybridization is weak because of the relatively long distance between Ni at I sites and N atoms. The XMCD signals of Mn and Ni atoms reverse sign between x = 0.1 and 0.25. This shows that the directions of the magnetic moments carried by Mn and Ni atoms are reversed, indicating that the magnetic compensation occurs in the range 0.1

The interactions between oxygen and Rh–Pd bimetallic alloy surfaces were investigated using surface sensitive experimental techniques and density functional theory calculations. The alloy surfaces were oxidized under 10−5 Torr and 100 mTorr oxygen upon heating above 250 °C. A thin Rh oxide layer was preferentially formed on a Rh1Pd9(100) surface, while a thin Pd oxide layer was formed on a Rh1Pd9(111) surface, though the Rh oxide is thermodynamically more stable irrespective of the surface orientation. Chemical analyses revealed that the initial Rh fraction for the (111) surface was significantly lower than that for the (100) surface, which suggests that the oxidized element on the surface is kinetically selected depending on the near surface initial composition.

Graphene-based vertical spin valves (SVs) are expected to offer a large magnetoresistance effect without impairing the electrical conductivity, which can pave the way for the next generation of high-speed and low-power-consumption storage and memory technologies. However, the graphene-based vertical SV has failed to prove its competence due to the lack of a graphene/ferromagnet heterostructure, which can provide highly efficient spin transport. Herein, the synthesis and spin-dependent electronic properties of a novel heterostructure consisting of single-layer graphene (SLG) and a half-metallic Co2 Fe(Ge0.5 Ga0.5 ) (CFGG) Heusler alloy ferromagnet are reported. The growth of high-quality SLG with complete coverage by ultrahigh-vacuum chemical vapor deposition on a magnetron-sputtered single-crystalline CFGG thin film is demonstrated. The quasi-free-standing nature of SLG and robust magnetism of CFGG at the SLG/CFGG interface are revealed through depth-resolved X-ray magnetic circular dichroism spectroscopy. Density functional theory (DFT) calculation results indicate that the inherent electronic properties of SLG and CFGG such as the linear Dirac band and half-metallic band structure are preserved in the vicinity of the interface. These exciting findings suggest that the SLG/CFGG heterostructure possesses distinctive advantages over other reported graphene/ferromagnet heterostructures, for realizing effective transport of highly spin-polarized electrons in graphene-based vertical SV and other advanced spintronic devices.

We study an electric field-induced redox reaction at the interface of GdOx/Co thin film, by means of soft X-ray absorption spectroscopy (XAS). The fluorescence-yield depth-resolved XAS analysis reveals that the interfacial Co layer at GdOx/Co is composed of ∼50% Co oxide when the negative field is applied, while metallic Co is dominant in the case of the positive field. We suppose that the interfacial layer is oxidized by oxygen migration from the GdOx layer with the negative field while the interfacial layer shows the metallic state with the positive field, which means that the redox reaction is induced by the electric field. In addition, it is found from the X-ray magnetic circular dichroism (XMCD) measurement that the orbital magnetic moment of Co is larger when the negative electric field is applied to the film, as compared to the positive field. Moreover, the depth-resolved XMCD analysis reveals that the interfacial Co layer shows no or little magnetization regardless of the electric field, while for the inner layer, an increase of the orbital magnetic moment is suggested with the negative field. The field-induced magnetic modification could be attributed to the change of the orbital moment in the inner Co layer due to interfacial modifications. We thus succeed in the direct observation of the redox reaction-induced change in the interface magnetic state.

XMCD is the difference in the X-ray absorption intensities between the right- and left-hand circular polarizations.

Soft X-ray absorption fine structure (SXAFS) is based on the excitation of core-level electrons to the unoccupied states around the vacuum level, which is accompanied with soft X-ray absorption. Since each element has its own core-level energy, the SXAFS provides with element-specific information.

Carbon nanotubes (CNTs) and epitaxial graphene on SiC substrates formed by thermal decomposition are of great interest for electronic and optoelectronic applications. The initial decomposition process of a SiC surface is critical to the formation of subsequent nanocarbon materials, such as CNTs or graphene. We present here an in situ near-edge X-ray absorption fine structure (NEXAFS) spectroscopy study of the initial formation processes of CNTs on the SiC C-face and graphene on the Si-face by thermal decomposition at high temperature. On both surfaces, desorption of Si atoms and subsequent graphitization of the remaining carbon atoms were observed above 1000 °C by carbon K-edge NEXAFS measurements in real time, but the incidence angle dependence of NEXAFS spectra showed marked difference between the SiC C-face and Si-face; on the SiC Si-face, the orientations of graphene layers are kept parallel to the surface during the graphene growth. In contrast, on the SiC C-face, graphene layers are initially orient...

A graphene nanoribbon is formed by the dehydrogenation reaction of n-alkane adsorbed on a Au(111) surface. The X-ray absorption spectra at the near carbon K-edge show the appearance of the out-of-plane 1s → π⁎ resonance upon heating the n-C44H90 monolayer with the simultaneous disappearance of the 1s → σ⁎CH/R (R: Rydberg state) resonance. The π⁎ resonance located at 284.6 eV reflects a high edge density and is consistent with the ribbon shape, which was observed by scanning tunneling microscopy, and the C 1s XPS peak at 284.0 eV.

The interaction between nitric oxide (NO) and Rh(111) surface has been investigated by a combination of near-ambient-pressure X-ray photoelectron spectroscopy, low energy electron diffraction, and density functional theory calculations. Under low-temperature and ultrahigh vacuum conditions, our experimental and computational results are consistent with the previous reports for NO adsorption phases on Rh(111). While at room temperature and upon exposure to gaseous NO of 100 mTorr, NO molecules partially dissociate followed by chemical removal of atomic nitrogen by NO from the surface, and the remaining atomic oxygen and NO form a NO/O mixed phase. Interestingly, this mixed phase is stable even after NO evacuation and shows a well-ordered (2 × 2) periodicity. These observations provide a new insight into the NO/Rh(111) system under near-ambient-pressure condition.

Catalytic CO oxidation over Pd(111) and Pd

We develop a fluorescence-yield depth-resolved soft x-ray absorption spectroscopy (XAS) technique, which is based on the principle that the probing depth is changed by the emission angle of the fluorescence soft x rays. Compared with the electron-yield depth-resolved XAS technique, which has been established in this decade, we can observe wider range in-depth XAS distribution up to several tens of nm. Applying this technique to a 30 ML (∼4.3 nm) FeCo thin film, we observe Fe L-edge XAS spectra at the probing depth of 0.3–6 nm and find that the film has 22 ML (∼3.1 nm) surface oxide layer while its inner layer shows metallic state. We thus successfully obtain nanometer-resolution depth-resolved XAS spectra and further expect that operando measurement under the electric and/or magnetic fields is possible.

We have studied the effect of cobalt substitution in $L{1}_{0}\ensuremath{-}{\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{Co}}_{x}\mathrm{Pt}$ films by means of x-ray magnetic circular dichroism (XMCD) and first-principles calculations. The magnetic moments of Fe ($\ensuremath{\sim}2.5\phantom{\rule{4pt}{0ex}}{\ensuremath{\mu}}_{\mathrm{B}}$) and Co ($\ensuremath{\sim}1.5\phantom{\rule{4pt}{0ex}}{\ensuremath{\mu}}_{\mathrm{B}}$) deduced using XMCD were almost unchanged upon Co doping, and the net magnetization decreases with increasing Co content. Calculation also showed that the $3d$ electrons that have been added by Co substitution occupy only spin-down bands.

The strong perpendicular magnetic anisotropy of $L{\rm1_0}$-ordered FePt has been the subject of extensive studies for a long time. However, it is not known which element, Fe or Pt, mainly contributes to the magnetic anisotropy energy (MAE). We have investigated the anisotropy of the orbital magnetic moments of Fe 3$d$ and Pt 5$d$ electrons in $L{\rm1_0}$-ordered FePt thin films by Fe and Pt $L_{2,3}$-edge x-ray magnetic circular dichroism (XMCD) measurements for samples with various degrees of long-range chemical order $S$. Fe $L_{2,3}$-edge XMCD showed that the orbital magnetic moment was larger when the magnetic field was applied perpendicular to the film than parallel to it, and that the anisotropy of the orbital magnetic moment increased with $S$. Pt $L_{2,3}$-edge XMCD also showed that the orbital magnetic moment was smaller when the magnetic field was applied perpendicular to the film than parallel to it, opposite to the Fe $L_{2,3}$-edge XMCD results although the anisotropy of the orbital magnetic moment increases with $S$ like the Fe edge. These results are qualitatively consistent with the first-principles calculation by Solovyev ${\it et\ al.}$ [Phys. Rev. B $\bf{52}$, 13419 (1995).], which also predicts the dominant contributions of Pt 5$d$ to the magnetic anisotropy energy rather than Fe 3$d$ due to the strong spin-orbit coupling and the small spin splitting of the Pt 5$d$ bands in $L{\rm1_0}$-ordered FePt., Comment: 9 pages, 4 figures, 2 tables

We investigated the high-density CO adsorption phase formed on a Pt(111) surface when exposed to CO gas of pressure ranging from UHV to 100 mTorr using near-ambient-pressure (NAP)-XPS. Combined results from the NAP-XPS measurements and DFT calculations reveal the adsorption structure of CO molecules in the dense CO overlayer, which is stable under realistic conditions.

We investigated the interactions of CO and O2 with Ru( 10 1 ¯ 0 ) single crystal surfaces, and studied the in-situ catalytic oxidation reaction of CO on the surface under near realistic pressure conditions by using a combination of near-ambient-pressure x-ray photoelectron spectroscopy and differential pumping mass spectroscopy. At lower temperatures (T

We show from the depth-resolved X-ray absorption analysis that the degree of surface oxidation of Fe70Co30 thin films is reduced by Ar+ ion milling even if the film is exposed to air after ion milling. The milled film has thinner surface oxide layer and smaller ratio of Fe oxide component in the surface layer than those of the as-deposited film. It is also indicated that selective oxidation of Fe proceeds accompanied by the movement of Fe atoms toward the surface. The suppression of oxidation is explained by the obstruction of Fe movement toward the surface by the milling-induced disorder.

The temperature-induced phase transition of the n-C36H74 monolayer on the monolayer graphene grown on a Pt(111) surface is studied by X-ray absorption fine structure spectroscopy in the carbon near the K-edge (C K-NEXAFS). The C K-NEXAFS spectra of the n-C36H74 monolayer is separated from the spectra of the monolayer graphene by subtraction. The σCC* resonance predominantly observed in the normal incidence (NI) spectra is consistent with a chain axis lying flat on the graphene sheet at 120 K (crystalline phase) and 300 K (smectic phase). The σCH*/R resonance at 287.2 eV is characteristic of the monolayer, which is attributed to the σCH* orbitals distributed in an open space above the monolayer. The intensity ratio of the resonance for grazing incidence (GI) spectra with respect to that for normal incidence (NI) spectra decreases as a function of the temperature, which reflects the orientation change of the carbon plane with respect to the graphene sheet, from perpendicular (edge-on) to parallel (flat-on) ...

CO oxidation reaction on a Pd(110) single crystal surface at various temperatures under near-ambient-pressure conditions has been investigated using in situ X-ray photoemission spectroscopy and mass spectroscopy. At lower temperature conditions, the CO2 formation rate is low, where the surface is covered by CO molecules (i.e., CO poisoning). Above a critical temperature 165 °C the Pd(110) surface converts to a catalytically active surface and is dominated by chemisorbed oxygen species. Further at the higher temperatures up to 320 °C, the CO2 formation rate is gradually decreased to about 80% of the maximum rate. At this moment, the amount of chemisorbed O was also decreased, which suggests that the CO oxidation reaction proceeds via the conventional Langmuir–Hinshelwood mechanism even under near-ambient pressure conditions.

We report molecular CO and NO adsorption structures on Pd(100) single crystal surfaces under sub-Torr pressure conditions at room temperature. A combination of ambient pressure X-ray photoelectron spectroscopy and density functional theory based calculations indicates that CO molecules adsorb at 2-fold bridge sites with (2√2 × √2)R45°, (3√2 × √2)R45° and (4√2 × √2)R45° structures under the CO gas pressures at room temperature. Furthermore a higher-density adsorption structure is reversibly formed at 0.5 Torr CO, where all the CO molecules keep sitting on the bridge sites. In case of NO adsorption, at 10 − 7 Torr, a (2√2 × √2)R45° structure with occupying bridge sites is formed, which is the same as the case of CO. However, subsequent gas introduction up to 0.5 Torr causes additional site occupation of on-top sites. Furthermore NO molecules partially dissociate into atomic N and O species but they disappear from the surface due to further reaction with NO under ambient conditions.

Spectral separation methods for X-ray absorption fine structure spectroscopy at the near carbon K-edge are examined for an n -C 36 H 74 monolayer adsorbed on a monolayer graphene grown on a Pt(1 1 1) surface. The spectra of n -C 36 H 74 and the monolayer graphene are separated by fitting decay curves obtained for all photon energies by detecting photoelectrons as a function of the ejection angle. The results are discussed in comparison with separation results obtained by subtracting the independently measured graphene spectra as a background.

We report x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) measurements of both paramagnetic and ferromagnetic Ti 1 − x Fe x O 2 − δ thin films. Fe L 3 , 2 edge XAS spectra showed that the Fe ions in our samples were in mixed valence states and that the Fe2+/Fe3+ ratio decreased with increasing oxygen partial pressure. Finite XMCD signals were observed only for the Fe2+ state in the ferromagnetic sample. These findings indicate that the observed ferromagnetism in Ti 1 − x Fe x O 2 − δ originates from ferromagnetic interactions between Fe2+ local spins.

Depth analysis using X-ray absorption fine-structure spectroscopy at the near carbon K-edge (C K-NEXAFS) was performed for self-assembled monolayers of 4-methylbenzenethiol (4-MBT) and 4-ethylbenzenethiol (4-EBT) on Au(1 1 1). On the basis of the polarization dependence of π * resonance intensity, the benzene rings of 4-MBT and 4-EBT were found to be tilted by 30 ± 10° and 60 ± 5° with respect to the Au(1 1 1) surface, respectively. The spectra were separated into two components according to their depth by fitting the intensity decay curves of the electrons emitted by X-ray absorption. The spectra for lower segments exhibited bands at almost identical energies with different intensities depending on the polarization between 4-MBT and 4-EBT. In contrast, the spectra for upper segments including the alkyl groups showed a marked difference in the location of the σ CC * resonance. The σ CC * resonance of the ethyl group predominantly observed in the 15° incidence spectrum of 4-EBT indicated that the ethyl group was directed perpendicularly.

X-ray photoelectron spectroscopy (XPS) is useful for in situ analysis of catalytically active surfaces under reaction conditions. We conducted in situ observations of CO oxidation on Pd single-crystal surfaces with different orientations under near ambient pressure (NAP) conditions with XPS. In this short review we compare catalytically active surfaces of Pd with the different orientations. Both surface oxides and atomic oxygen chemisorbed on metallic surfaces can be active for CO oxidation depending on surface geometric structure. We propose similarity between the surface oxides and the chemisorbed oxygen from a viewpoint of availability of active oxygen. Catalytic activity of the metallic surface under NAP condition is also compared with that under ultrahigh vacuum conditions.

A new soft x-ray beamline BL-2B at Photon Factory of High Energy Accelerator Research Organization (KEK-PF) covers energy range from vacuum ultraviolet (30 eV) to soft x-ray (4000 eV). This wide energy range could be achieved by employing two undulators and two monochromators. Two different energy range undulators were installed tandem to a 9-meter straight section of PF storage ring. The 1st undulator is for VUV (30 eV) to SX (280 eV), while the other one is for SX (280 eV) to HX (4000 eV). It is also necessary to be equipped with two different monochrometors for energy above and under 2000 eV; grating monochrometor and double crystal monochrometor. One of the main purposes of this bemaline is spectroscopic study of light elements contained in several functional materials. The beamline is designed for photoemission spectroscopy (PES), X-ray absorption fine structure (XAFS) and other types of experiments. The performance of the new beamline is reported and typical examples of its application to material science are demonstrated.

To understand the electronic-structure changes of electrode materials during the charge/discharge processes is one of the most important fundamental aspects to improve the battery performance. Soft X-ray absorption spectroscopy (XAS) was used to study a bimetallic NiFe Prussian blue analogue electrode. XA spectra were obtained during the charge/discharge and were analyzed by the configuration-interaction full-multiplet (CIFM) calculation, in which the strong charge transfer due to the σ/π-donation and back-donation of cyanide was taken into account. The CIFM calculation revealed that the metal-to-ligand charge transfer (MLCT) played an important role in the electronic state of Ni–N bond. The Fe3+–C bond in the charged state is dominated by both the MLCT and ligand-to-metal charge transfer (LMCT), whereas only the MLCT strongly affects the Fe2+–C bond in the discharged state.

The CO oxidation reaction on the Pd(111) model catalyst at various temperatures (200–400 °C) under hundreds mTorr pressure conditions has been monitored by in situ ambient pressure X-ray photoelectron spectroscopy and mass spectroscopy. In situ observation of the reaction revealed that the Pd(111) surface is covered by CO molecules at a lower temperature (200 °C), while at higher temperatures (300–400 °C) several oxide phases are formed on the surface. We found that the reactivity is enhanced in the presence of a surface oxide and significantly suppressed by formation of a cluster oxide and the PdO bulk oxide. CO titration experiments suggest that less coordinated oxygen atoms are more reactive for CO oxidation.

1D hydrogen bond chains of D2O molecules formed on a Pt(211) stepped surface are observed by polarization dependent near O K-edge X-ray absorption fine structure spectroscopy (O K-NEXAFS). The 1s→ σ*OD resonance at 535.0 eV in the normal incidence O K-NEXAFS spectrum corresponds to the free OD bond oriented perpendicularly to the step lines, and the resonance at 540.0 eV is related to the hydrogen bond extended in a zigzag manner parallel to the step lines. A structural model consistent with these observations is obtained from the DFT optimization, in which all of the molecules act as one hydrogen donor and acceptor in the 1D chain.

Formation process of carbon nanocaps, which are formed at the beginning of carbon nanotube (CNT) growth by surface decomposition of SiC, was investigated by scanning tunneling microscopy (STM) and in situ near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. As Si atoms were desorbed, carbon nanoparticles 1–2 nm in diameter were accumulated on SiC(000-1) surfaces. At around 1200 °C, these were coalesced and crystallized to carbon nanocaps. In addition, just before the crystallization, majority of C–C bonds were directed nearly parallel to the surface. Based on these experimental results, we proposed a model for carbon nanocap formation, which plays an important role to determine the CNTs.

Near edge X-ray absorption fine structure spectra at the carbon K-edge (C K-NEXAFS) of n-C12H26 films grown on graphite (0 0 0 1) were measured under ultrahigh vacuum conditions. In the normal incidence spectra, the 1 s → σ CH * / R resonance of n-alkane was identified at a lower energy than the absorption edge of graphite. The σ CH * / R resonance directed along the CH bond was observed at 286.9 eV for the first layer of the n-C12H26 film on graphite. This indicates that the CCC plane of the molecule is parallel to the surface (flat-on orientation). As the film thickness increases, another peak assigned to σ CH * / R ⊥ grows at 288.0 eV, suggesting an increase in the number of molecules with the CCC plane perpendicular to the surface in a multilayer film.

An incommensurate crystalline phase of the (sub)monolayer of n-C36H74 lying on graphite (0001) is observed on cooling the smectic phase using normal incidence near edge X-ray absorption fine structure spectroscopy at the carbon K-edge (NI C K-NEXAFS) and scanning tunneling microscopy (STM). The orientation of the CCC plane of the all-trans alkyl chain with respect to the substrate is confirmed by the 1s → σCH*/R resonance detected by the NI C K-NEXAFS spectra at the absorption edge. Almost all molecules take the parallel (flat-on) orientation in the smectic phase, and at least half of them change to the perpendicular (edge-on) orientation in the incommensurate crystalline phase. A lamellar structure with a width corresponding to the chain length and no internal structure is observed by STM in the smectic phase, whereas that in the incommensurate crystalline phase exhibits a ladder-like structure with a periodicity of ca. 2 nm transverse to the chain direction. The periodicity is incommensurate with the su...

The present status of a new vacuum ultraviolet/soft X-ray (VUV/SX) beamline (BL-13A) used for the study of organic thin films adsorbed on surfaces is described. The base pressure of BL-13A is maintained below 1×10−8 Pa in order to prevent contamination of the optics by residual gases. The measured performance is as follows: photon-energy region, 30-1,200 eV; photon flux, 109-1011 photons s−1; photon-energy resolution (E/ΔE), 10,000 at a photon energy of 401 eV; spot size (horizontal\ imes;vertical) at the second focus, ≈630×120 μm; photon-energy drift, ≤±0.02 eV at a photon energy of 244.39 eV; reduction of photon flux in the C K-edge region, ∼50%.