村松 康司

For the analysis of fluorine materials and 3d transition metals by soft-x-ray absorption spectroscopy, A new diffraction grating with multilayer coating was installed at the BL-10 beamline of the NewSUBARU synchrotron light source. The target photon energy range of this grating is from 500 eV to 1,000 eV, which includes absorption edges of fluorine and 3d transition metals. The beam intensity of BL-10 in this range was very low due to low reflectance of the diffraction grating for the usage of monochromator. In order to obtaining high reflectance, we developed wideband W/Si multilayer and this multilayer was coated on a new diffraction grating. The reflectance of this multilayer was approximately 13-times higher than that of previous Ni single layer at the fluorine absorption energy edge of 697 eV. The beam intensity at the energy of 697 eV using the new diffraction grating was over 40 times stronger than that using the previous Ni-coated diffraction grating. As the result, using the new diffraction grating, it can be observed that the high-quality absorption spectrum of EUV resist at the absorption edge of fluorine and standard materials of 3d transition metals. The results show that the W/Si multilayer coating significantly improved the performance of the grating at the target energy range.

Simultaneous achievement of high sensitivity and low line edge roughness (LWR) is necessary in EUV resist. The chemical reaction analysis of EUV (Extreme Ultraviolet) chemical amplified (CA) resist and acid diffusion length evaluation was carried out. In order to achieve low LWR of the CA resist, the large chemical structure of the anion of photoacid generator (PAG) is required for shortening the acid diffusion length. On the other hand, in order to increase the sensitivity, on the basis of the chemical reaction analysis using the soft x-ray absorption spectroscopy, the decomposition reaction of the large chemical structure of the PAG anion should be taken in account in addition of ionization reaction. However, if the decomposition reaction occur, the acid diffusion length will become shorter than that as expected. It is found that the Imidate-type of anion of PAG has high sensitivity and short diffusion length. The chemical reaction analysis by the soft x-ray absorption spectroscopy using the synchrotron radiation with the combination analysis of the acid diffusion are useful method for the mitigation of high sensitivity and low LWR.

Graphene layers with silica pillars which widen. the interlayer distance and functionalize the space as micropores have been prepared as one of the new porous carbon materials. In this study, the silica-pillared graphene with Fe-N units as a catalytic active site for cathodic oxygen reduction was formed as a new type of carbonaceous noble-metal-free oxygen reduction catalysts with the ordered pore structure. The formation of the pillared carbon was performed by introducing silylating reagents as the pillar source and also as the nitrogen source of the units in the graphite oxide interlayer spaces, introducing the Fe ions, and heat treatment in vacuum at 500 degrees C. The X-ray diffraction (XRD) patterns showed the ordered layered structure. The X-ray absorption fine structure (XAFS) of the Fe-K edge showed that the unit was a square planar Fe-N-4 moiety. The catalytic activity for the O-2 reduction was demonstrated by measurements using rotating disk electrodes with the pillared carbon fixed on the surface and immersed in an oxygen-saturated acidic solution. The activity was enhanced by the combination of the nitrogen containing compound to the silylating reagent and using the nitrogen-rich silylating reagent. (C) 2013 Elsevier Ltd. All rights reserved.

To clarify the electronic structure of metallic heavily boron (B)-doped diamonds, the discrete variational (DV)-X alpha method was used to analyze the continuous X-ray absorption near edge structure (XANES) in the BK and CK regions of a 71,000-ppm B-doped diamond. The continuous XANES profiles are well reproduced by the unoccupied B2p- and C2p-DOS of the caged B-cluster models, in which an octahedron B-6 cluster, a cuboctahedron B-12 cluster, or an icosahedron B-12 cluster is inserted into the defect space of the diamond lattice. The delocalized conduction band structure can be understood from the hybridization of the B atoms in B-clusters with the surrounding C atoms in the diamond lattice. The results indicate that the B atoms in heavily B-doped diamonds form caged B-clusters in the defect space of the diamond lattice. (C) 2013 Elsevier B.V. All rights reserved.

To evaluate nitrogen in graphitic carbon materials, we propose a simple quantitative and fingerprint analysis method, which measures the total electron yield X-ray absorption spectra (TEY-XAS) of aromatic compounds possessing typical nitrogenated functional groups as standard samples, and fingerprint analysis is performed using the X-ray absorption near edge structure (XANES) in the N K and C K regions. The relationship between the atomic ratio of nitrogen to carbon (N/C) and the X-ray absorption intensity ratio of N K edge to C K edge (N K sigma*/C K sigma*) of standard samples yields a working curve to quantitatively analyze nitrogen. The successful application to carbon nitride films demonstrates that the proposed method is capable of quantitative and fingerprint analysis. (C) 2013 The Japan Society of Applied Physics

The chemical reaction in EUV irradiation of the several photoacid generators (PAGs) which employed triphenylsulfonium (TPS) salts as the cation of PAG, is discussed on the basis of the analysis using the SR absorption spectroscopy in the soft x-ray region. The fluorine atoms of the anion PAGs which have the chemical structure of the imidate type such as TPS-Imidate-1, and TPS-Imidate-2 strongly decomposed under EUV exposure. In the case of these FAG type, it is found that in addition to the ionization reaction, the anion decomposition reaction originated by the photo excitation of the photoacid generator might occur under EUV exposures. Thus the sensitivity seemed to be high comparison to tri-phenylsulfonium perfluorobutanesulfonate (TPS-Nonaflate) under EUV exposure. In the case of tri-phenylsulfonium camphorsulfonate (TPS-Cs), the anion which does not contain fluorine seemed to be very stable under EUV exposure and the sensitivity is lower than TPS-Nonaflate.

The chemical state of nitrogen in nitrogen-entrapped carbon nanohorns (N-CNHs) synthesized by submerged arc discharge in liquid nitrogen was determined by soft X-ray emission and absorption spectroscopy using synchrotron radiation. X-ray absorption spectra (XAS) and X-ray emission spectra (XES) in the CK and NK regions of the N-CNHs were measured at the Advanced Light Source. From fingerprint analysis in NK-XAS and by referring to nitrogen-containing aromatic compounds, the suggested chemical state of nitrogen in N-CNHs is imine. Theoretical analysis of NK-XES using the discrete variational X alpha molecular orbital calculations elucidated that the local structure of N-CNHs is chemisorption of N-2, forming pentagonal and/or hexagonal rings with carbon atoms at the graphitic layer edges, which assume an imine structure. Therefore, the entrapped nitrogen in N-CNHs is chemisorbed at the edges of the graphitic layers.

The chemical states of organic semiconductors were investigated by total-electron-yield soft X-ray absorption spectroscopy (TEY-XAS); and first-principles calculations. The organic semiconductors, pentacene (C22H14) and pentacenequinone (C22H12O2), were subjected to TEY-XAS and the experimental, spectra obtained were compared with the Is core-level excited spectra of C and 0 atoms, calculated by a first-principles planewave pseudopotential method. Excellent agreement between the measured and the calculated spectra were obtained for both materials. Using this methodology, we examined the chemical states of the aged pentacene, and confirmed that both C-OH and C=O chemical bonds are generated by exposure to air. This result implies that not only oxygen but also humidity causes pentacene oxidation.

Various carbon materials with a characteristic morphology and pore structure have been produced using template methods in which a carbon-template composite is once formed and the characteristic features derived from the template are generated after the template removal. In this study, hemoglobin, which is a natural compound that could be abundantly and inexpensively obtained, was used as the carbon material source to produce a carbonaceous noble-metal-free fuel cell cathode catalyst. Magnesium oxide was used as the template concurrently generated with the hemoglobin carbonization from magnesium acetate mixed with hemoglobin as the starting material mixture to enable pore development for improving the activity of the carbonized hemoglobin for the cathodic oxygen reduction. After removal of the MgO template, the substantially developed pores were generated in the carbonized hemoglobin with an amorphous structure observed by total-electron-yield Xray absorption. The extended X-ray absorption fine structure at the Fe-K edge indicated that Fe was coordinated with four nitrogen atoms (Fe-N-4 moiety) in the carbonized hemoglobin. The oxygen reduction activity of the carbonized hemoglobin evaluated using rotating disk electrodes was dependent on the pore structure. The highly developed pores led to an improved activity.

The local structure of boron-doped highly oriented graphite films was determined via soft x-ray emission and absorption spectroscopy using synchrotron radiation. Analysis of the BK and CK x-ray emission spectra using the discrete variational-X alpha molecular orbital method clarified that boron atoms are chemisorbed onto graphite by substituting for carbon atoms in the carbon hexagonal rings. Compared to graphite, boron-doped graphite exhibits spectral differences in the higher edge of the CK x-ray emission spectrum and the CK x-ray absorption edge. Such a spectral profile of boron-doped graphite, which reflects the band structure, is well explained by the chemisorbed boron structure. (C) 2011 American Institute of Physics. [doi:10.1063/1.3631108]

カキ殻が持つ特長を活かしながら，低コストで環境負荷イオンを効率よく除去するための処理法確立を目的として，カキ殻の熱処理条件について検討した。<BR>適切な窒素ガス流量で焼成すれば1気圧での炭酸カルシウムの分解温度である900℃よりもはるかに低い600℃でカキ殻表面の改質ができ，リン酸イオンや硫酸イオンおよびカドミウムイオンを効率よく除去できることを明らかにした。オゾンや空気雰囲気では600℃で熱処理した場合にリン酸イオン除去率の低下が見られた。熱処理カキ殻によるイオン除去性は高い順にカドミウムイオン，リン酸イオン，硫酸イオンであった。

Adsorbents for removing cadmium ions from water were synthesized from inorganic wastes such as oyster shells, drinking-water-treatment sludge (DWTS), and waste glass. The oyster shells and DWTS were pretreated by heating for 2 h at 1173 K before hydrothermal synthesis was started. The Al/(Al+Si) ratio was adjusted, and then, the mixture of pretreated materials was hydrothermally treated in a sodium hydroxide solution for 72 h at 423 K to synthesize the adsorbents. The synthesized adsorbent specimens were characterized by X-ray diffraction (XRD), thermogravimetric-differential thermal analysis (TG-DTA) measurements, and scanning electron microscopy (SEM). The main components of these specimens were aluminum-substituted tobermorite and sodalite. The formation of sodalite was dependent on the mass ratio of DWTS to glass. The maximum amount of cadmium ions were removed when the mass ratio of the pretreated material was 1:1:1. In the cadmium removal test, the adsorbent with this mass ratio removed almost 100% of the cadmium in a solution with a concentration of 10 mg L-1. Even in the presence of a 1000-fold excess of potassium ions or 10000-fold excess of sodium ions, approximately 80% of the cadmium ions were removed.

Adsorption structure of the entrapped nitrogen in carbon-nanohorns, which are synthesized by submerged arc-discharge with carbon electrodes in liquid nitrogen, has been analyzed by soft X-ray emission and absorption spectroscopy using synchrotron radiation. From spectral analysis using the discrete variational (DV)-X alpha molecular orbital method, it is elucidated that the most probable structure is the chemisorption of N-2 at the edges of hexagonal carbon layers. The adsorbed N-2 forms a pentagonal or a hexagonal ring with the edge carbon atoms in the zigzag or armchair arrangements, respectively. (C) 2010 Elsevier B.V. All rights reserved.

A graphite-like layered material of composition BCxNy (x=2.0-2.4, y=0.8-0.9), which is called BC2N in this paper, was prepared by a chemical vapor deposition method at 1770-2220 K. Lithium (Li) and potassium (K) were intercalated into BC2N by an electrochemical method and a vapor-phase reaction, respectively, to make the first-stage compounds with interlayer spacings similar to those of the first-stage graphite intercalation compounds. Sodium (Na) was intercalated into BC2N by the electrochemical method as well as the vapor-phase reaction, whereas Na was hardly intercalated into graphite. The X-ray diffraction analysis and an electrochemical capacity suggested that the Na-intercalated BC2N was a mixture of the first- and second-stage compounds. X-ray absorption spectroscopy indicated that an unoccupied pi(*) orbital of BC2N showed a relatively strong intensity, and the bottom of the orbital was at an energy lower than each bottom of graphite, noncrystalline carbon, and BC6N. These results suggested that alkali metals including Na could donate electrons to BC2N more efficiently than the other host materials. Thus, the intercalation of alkali metal into BC2N proceeds more effectively than the other host materials.

We used the discrete variational (DV)-X alpha method to analyze the high-resolution soft X-ray emission and absorption spectra in the CK region of titanium carbide (TiC). The spectral profiles of the X-ray emission and absorption can be successfully reproduced by the occupied and unoccupied density of states (DOS), respectively, in the C2p orbitals of the center carbon atoms in a Ti62C63 cluster model, suggesting that the center carbon atom in a large cluster model expanded to the cubic-structured 5(3) (= 125) atoms provides sufficient DOS for the X-ray spectral analysis of rock-salt structured metal carbides. (C) 2009 Wiley Periodicals, Inc. Int J Quantum Chem 109: 2722-2727, 2009

The electronic structure of carbon nanohorns (CNHs) was calculated by the discrete variational -X alpha molecular orbital method to analyze the electronic structure and/or chemical state using soft X-ray spectroscopy. Five isomers of CNH,C115H25, C158H26, C135H21, C102H16, and C118H16, were successfully modeled. Slight differences in the electronic structure between the hexagonal and pentagonal rings of the CNH models can be understood from the orbital population, net charge, and bond overlap population. The calculated density of states in the C2p orbitals can be used for spectral analysis of soft X-ray emission and absorption in the CK region of CNH. (C) 2009 Wiley Periodicals, Inc. Int J Quantum Chem 109: 2728-2733, 2009

To elucidate the possibility of quantitatively analyzing sp(2)-hybridized carbon (sp(2)-C) and sp(3)-C in carbon materials using total-electron-yield (TEY) X-ray absorption spectra (XAS) in the C K region, we measured the TEY-XAS of mixtures of multi-walled carbon nanotubes or carbon black as sp(2)-C sources and diamond as an sp(3)-C source. The measured relationship between the pi*/sigma* peak intensity ratio in the C KTEY-XAS and the weight (atomic)% of sp(2)-C can be successfully explained by the summed TEY of the sp(2)-C and sp(3)-C components and considering the TEY efficiency of sp(3)-C relative to sp(2)-C, k. However, the experimentally determined k values show that TEY of the sp(3)-C is much smaller than that of sp(2)-C by about one order of magnitude, even depending on the chemical form and/or electronic properties of individual carbon components. This suggests that further evaluation of the TEY efficiency is necessary prior to the quantitative sp(2)/sp(3) analysis of carbon materials using the TEY-XAS. (C) The Japan Society of Applied Physics

A new quantitative and chemical-state analysis method to measure oxygen on the surface of graphitic carbon materials by total-electron-yield soft X-ray absorption spectroscopy (TEY-XAS) is proposed, and applied to the analysis of graphite oxides (GO). In this method, working curves for quantitative analysis were successfully obtained from the relative absorption- peak-intensity in the OK and CK absorption edges as functions of the O/C atomic ratio in standard organic samples which have various oxygenated functional groups. The atomic ratio O/C on the GO surface was determined as approximately 0.35 from the working curves, and the chemical states of surface oxygen were estimated as mainly –OH and partially >C=O and/or –CH=O from the finger print method of the TEY-XAS.

To investigate the local structure of carbon black (CB) crystallites, soft X-ray absorption spectra (XAS) in the CK region of CB were measured using synchrotron radiation, and the π^* peak profile in the CK-XAS was analyzed by the discrete variational (DV) Xα method. Compared to highly oriented pyrolytic graphite (HOPG), CB exhibits a broader π^* peak profile where the intensity of the broad portion in CB is proportional to the hydrogen occluded in the CB. However, the broad portion cannot be reduced even in H₂-degassed CB by thermal desorption. These findings on the broad π^* peak profile can be simulated by the unoccupied C2p density of states (DOS) of the carbon atoms that form the nonbenzenoid rings and hydrogenated edge carbon atoms. Therefore, plausible origins for the broad π^* peak in the CK-XAS of CB are the nonbenzenoid structure and/or hydrogenated edge carbon atoms in the graphitic crystallites.

The distribution of lead (Pb) accumulated ill the pteridophyte Blechnum niponicum, a Pb-hyperaccumulator, was measured using synchrotron-radiation micro X-ray fluorescence (SR-mu-XRF) at BL37XU of SPring-8. From two-dimensional (2D) imagings of Pb at the root, petiole, leaf vein, pinna epidermis and sorus in the Blechnum niponicum, the mechanism for the transportation and accumulation of Pb can be suggested to be as follows: Lead is accumulated in conductive tissues. Most of the Pb solubilized in the rhizosphere is fixed in the conductive tissue, with the remainder being transported with the transpiration stream to the above-ground parts of the plant. Lead transported to the upper parts of the plant ultimately remains at the terminal points of the transpiration stream, including the stomatal apparatus and water pores; it was shown that these sections contain high concentrations of Pb.

The L2,3 X-ray emission spectra of Cu metal and its oxides (Cu2O and CuO) have been measured by using monochromatic synchrotron radiation. From the analysis of spectra recorded at different excitation energies, the Lβ1/Lα1,2 X-ray emission intensity ratio, i.e., I(L2)/I(L3) is discussed. The intensity ratio, I(L2)/I(L3) is found to show significant enhancements for the compound materials such as Cu2O and CuO, at resonance energy. At non-resonant high energy, I(L2)/I(L3) for CuO is observed to be higher than those for Cu and Cu2O. These tendencies are explained to be resonant or non-resonant excitation/deexcitation processes and absorption coefficients, including the chemical bonding effects. © 2008 Elsevier Ltd.

To analyze the local structure and/or chemical states of boron atoms in boron-doped diamond, which can be synthesized by the microwave plasma-assisted chemical vapor deposition method (CVD-B-diamond) and the temperature gradient method at high pressure and high temperature (HPT-B-diamond), we measured the soft X-ray emission spectra in the CK and BK regions of B-diamonds using synchrotron radiation at the Advanced Light Source (ALS). X-ray spectral analyses using the fingerprint method and molecular orbital calculations confirm that boron atoms in CVD-B-diamond substitute for carbon atoms in the diamond lattice to form covalent B-C bonds, while boron atoms in HPT-B-diamond react with the impurity nitrogen atoms to form hexagonal boron nitride. This suggests that the high purity diamond without nitrogen impurities is necessary to synthesize p-type B-diamond semiconductors.

Electronic structure of graphite-like layered material with a composition of BC6N, which was prepared at 1470 K by the chemical vapor deposition (CVD) method, was investigated by X-ray emission spectroscopy (XES) and X-ray absorption spectroscopy (XAS) using synchrotron radiation. The X-ray emission and absorption spectra in the BK, CK and NK regions of BC6N were considerably different from those of h-BN and graphite, probably because of a hybridization for orbitals of boron, carbon and nitrogen existing in the same layer of BC6N. Angle-resolved XES and XAS indicated the structural orientation of the BC6N film, which was also observed by X-ray diffraction (XRD) analysis. Density of states (DOS) in the occupied 2p orbitals calculated by the discrete variational (DV)-X alpha method for one (type A) of structural models which was considered on the basis of the CVD reaction, fitted with the measured X-ray emission spectra of BC6N. The intercalation phenomena of alkali metal into BC6N are similar to those of graphite, which is probably due to the band overlap and the relatively large DOS of the unoccupied pi* orbital of the material. (C) 2007 Elsevier Ltd. All rights reserved.

We have performed X-ray magnetic circular dichroism (XMCD) and valence-band photoemission studies of the diluted ferromagnetic semiconductor Zn1-xCrxTe. XMCD signals due to ferromagnetism and paramagnetism and/or superparamagnetism were observed at the Cr 2p absorption edge. Comparison with atomic multiplet calculations suggests that the magnetically active component of the Cr ion was divalent under the tetrahedral crystal field with tetragonal distortion along the crystalline a-, b-, and c-axes. In the valence-band spectra, spectral weight near the Fermi level was strongly suppressed, suggesting the importance of Jahn-Teller effect and the strong Coulomb interaction between the Cr 3d electrons. (C) 2008 The Japan Society of Applied Physics.

We measured the soft X-ray emission spectra (XES) in the C and F K-regions of graphite fluoride (CF)(n) by suppressing sample decomposition due to synchrotron radiation (SR) excitation, and analyzed the X-ray spectral features using the DV-X alpha method. The high-energy peak in the C K-spectra is assigned to the pi transition due to the C 2p hybridized with the F 2p orbitals. The XES can be successfully reproduced by calculated C and F 2p density of states (DOS) of a stretched C-F bond model in which the C-F bond length is longer than the typical length of 1.397 angstrom.

The discrete variational (DV)-X alpha method was used to analyze the high-resolution soft X-ray absorption spectra (XAS) in the C K-region of sputtered amorphous carbon films and carbon black to elucidate their local structures. The measured XAS of amorphous carbon and carbon black were compared with those of reference compounds, and the fine structure in the XAS can be assigned by the calculated density of states of the reference compounds. Such a comparative analysis in the measured XAS and the calculated density of states of these carbon materials with reference compounds, which have been known their local or molecular structures, is a valid approach for elucidating the complex local structures of carbon materials.

Ca1-x Srx RuO3, which is ferromagnetic for Sr concentration x>0.3, has been studied by x-ray magnetic circular dichroism (XMCD) in Ru 3p and O 1s core-level x-ray absorption. XMCD signals appear at x ∼ 0.3 and monotonically increase with x in the ferromagnetic phase. While the monotonic increase of the XMCD signals with x is of a typical Stoner-type, the absence of appreciable change in the spectral line shapes of both the Ru 3p and O 1s XMCD spectra indicate that the itinerant-electron ferromagnetism in Ca1-x Srx RuO3 is influenced by strong electron correlation. © 2007 The American Physical Society.