村松 康司

The development of highly reflective multilayer mirrors for use in the wavelength region around 6 nm is desired for X-ray photoemission spectroscopy for inner-shell excitation using a Schwarzschild objective. For this application, reflectivity is the most critical parameter determining the performance of multilayer mirrors, because the reflectivity of multilayers in the 6 nm region is generally very low. We have designed CoCr/C multilayer mirrors with a comparatively high reflectivity at around normal incidence and have fabricated them by magnetron sputtering. The measured peak reflectivity is about 16% at a wavelength of around 6 nm and an incident angle of 88°. The reflectivity remains almost constant for 4 h under 300°C in an Ar atmosphere.

To analyze the oxidation states of the graphitic surface of microporous carbon, soft X-ray absorption spectra in the 0 K region have been obtained for microporous carbon and various aromatic compounds. The aromatic molecules studied are substituted with one or more of the following oxygenated functional groups: hydroxy (-OH), carboxy (-COOH), carbonyl (>C=O), formyl (-CH=O), and ether (-O-). From comparison of the soft X-ray absorption spectra of microporous carbon and of reference aromatic compounds, the most probable chemical bonding states of oxygen in microporous carbon are found to be -COOH and >C(H)=O. Spectral features in the soft X-ray absorption spectra of microporous carbon are well explained by the O2p density of states in these oxygenated functional groups from discrete variational (DV)-Xα molecular orbital calculations.

The development of highly-reflective multilayer mirrors for use in the 6-nm region is desired for X-ray photoemission spectroscopy for inner-shell excitation using a Schwarzschild objective. For this application, reflectivity is the most critical parameter determining the performance of multilayer mirrors, because the reflectivities of multilayers in the 6-nm region are generally very low. We have designed CoCr/C multilayer mirrors with a comparatively high reflectivity at around normal incidence and have fabricated them by magnetron sputtering. The measured peak reflectivity is about 11.5% at a wavelength of around 6 nm and an incident angle of 88°. Thermal annealing was found to markedly improve the reflectivity, and a high value of 13% was obtained by annealing at 400 in an Ar atmosphere for 1 h. © 2001 Elsevier Science B.V. All rights reserved.

A Ni/Ti-based multilayer with thin interleaved carbon layers (Ni/C/Ti/C multilayer) has been designed and fabricated for the reflection coating of a grazing-incident-angle reflector in the water-window region for use in X-ray photoemission spectroscopy. It was found to be a highly reflective mirror at wavelengths just above the Ti absorption edge (around 2.73 nm), as designed. A Ni/C/Ti/C multilayer with 0.2-nm-thick interleaved carbon layers was fabricated by magnetron sputtering. The measured reflectivity was 40% at a wavelength of 2.76 nm and an incident angle of 9.5°. This value is a little bit higher than that for a Ni/Ti multilayer with almost the same layer structure. Furthermore, the addition of thin carbon layers was found to significantly improve the heat resistance of a multilayer. © 2001 Elsevier Science B.V. All rights reserved.

Soft X-ray emission spectra in the O K region of oxygen incorporated in microporous carbon were measured using synchrotron radiation, in order to observe directly the oxygen on the graphitic surface in micropores and obtain information about its chemical bonding states. The O K X-ray emission spectra of the microporous carbon exhibited a main peak at 526 eV with a low-energy tail, and the reference compounds also exhibited similar spectral features. A spectral feature analysis of the reference compounds using discrete variational Xα molecular orbital calculations showed that the measured 526-eV peaks of the microporous carbon may be due to O2p orbitals and the low-energy tails be to the hybridized O2p/O2s orbitals.

Partial-fluorescence-yield (PFY) x-ray absorption measurements, using the optimized window widths of position sensitive detectors in wave-length dispersive x-ray spectrometers, have been applied for radiative-process-resolved (RPR) x-ray absorption spectroscopy. We have measured PFY-absorption spectra of graphite and diamond at the C K threshold and of h-BN and c-BN at the B K threshold. Resonant elastic x-ray scattering was observed in graphite and h-BN on their PFY-absorption spectra, and excitonic x-ray scattering was observed in diamond and c-BN. These results show that PFY-absorption measurements for RPR x-ray absorption spectroscopy can provide the information about the electronic structures and the radiative-decay process in inner-shell excitation.

The performance of a soft X-ray emission spectrometer employing a charge-coupled device camera was examined in the energy range of 80-1250eV. The spectra observed by low-energy electron irradiation for metal L, oxygen K and silicon L lines were in good agreement with the previous observations by conventional MCP detectors. The results suggest that the energy resolution is good enough, for the resonant excitation spectroscopy by synchrotron radiation as well. © 2001 Elsevier Science B.V. All rights reserved.

Soft X-ray emission and absorption spectra in the C K region of amorphous carbon films systematically deposited by RF, ion-beam, and ECR sputtering under various deposition conditions were measured using highly brilliant synchrotron radiation. A broad main peak and a high-energy shoulder were observed in the emission spectra, and a fine structure consisting of at least five peaks was observed in the absorption spectra. By analogy to the occupied/unoccupied C2p-DOS obtained by DV-Xα molecular orbital calculations of simple cluster models composed of sp2 and sp3 carbon atoms, we approximately explained the spectral features in the measured X-ray emission spectra by σ and π bonds and estimated the fine structures in the absorption spectra by the hybridized unoccupied molecular orbitals formed by the local-structures composed of sp2 and sp3 carbon atoms. © 2001 Elsevier Science Ltd.

Soft X-ray emission and absorption spectra in the O K region of oxygen incorporated in microporous carbon were measured using synchrotron radiation, in order to directly observe the oxygen and identify its chemical bonding states on the graphitic surface in microporous carbon. The O K X-ray emission spectrum exhibits a peak at 526 eV with a low-energy tail, and the absorption spectrum at the O K threshold exhibits a sharp peak at 531.5 eV and then rises from 535 eV. Spectral feature analysis using DV-Xα molecular orbital calculations show that the measured X-ray spectra are not sufficiently explained by H2O or typical substituents, such as -OH, -CHO, and -COOH, on the graphitic surfaces. © 2001 Elsevier Science Ltd.

Soft x-ray emission and absorption spectra in the C K region of Mo/SiC/Si multilayer mirrors were measured using highly brilliant synchrotron radiation to identify the chemical bonding states of the buried silicon carbide layers. Comparison with the C 2p density of state (DOS) spectra, calculated by discrete variational-Xα molecular orbital calculations, of several SiC-based cluster models showed that the measured x-ray spectra approximately agreed with the calculated C 2p-DOS spectra of the c- and h-SiC-based SiCx models in which some silicon atoms were replaced by carbon atoms. The chemical bonding states of the silicon carbide layers in the Mo/SiC/Si multilayer mirrors were therefore estimated to be carbon-excessive silicon carbide. © 2000 American Institute of Physics.

The possible configurations of benzene and pyridine molecules adsorbed in microporous carbon were analyzed by synchrotron-radiation-excited soft X-ray emission spectroscopy and by analyzing its spectral features using DV-Xα molecular orbital calculations. The distances between the adsorbed molecules and the graphitic surface were estimated to be approximately 0.33 nm in both benzene- and pyridine-adsorbed systems. Both molecular orientations were also estimated to be almost parallel to the graphitic surface of microporous carbon. The electronic states of benzene and pyridine molecules adsorbed on the graphitic surface were similar to those of individual nonadsorbed free molecules. Therefore, the adsorption of benzene and pyridine molecules in the microporous carbon can be confirmed to be physisorption, and there is little charge-transfer between the adsorbed molecules and the graphitic surface.

High-resolution soft X-ray emission and absorption spectra in the C K region of hydrofullerene, which probably consists mainly of C60H36, were measured using highly brilliant synchrotron radiation to identify its molecular structure and electronic structure. Comparison with the C2p-DOS spectra, calculated by discrete variational (DV) Xα molecular orbital calculations, of three possible C60H36 isomers, showed that the measured X-ray spectra approximately agreed with the calculated C2p-DOS spectra of the T-symmetry isomer. The X-ray spectral features were explained by the electronic structure hybridized between the sp2 and sp3 carbon atoms of the T-symmetry C60H36. © 2000 Elsevier Science B.V.

Si Kβ X-ray emission spectral features of cubic silicon molecules, octasilacubane and octasilasecocubane, were identified by discrete variational (DV) Xα molecular orbital calculations. Their Si Kβ X-ray emission spectra were precisely reproduced by the ground-state Si3p-DOS spectra. By comparing the measured Si Kβ X-ray emission spectra with the calculated Si3p-DOS spectra, the X-ray emission spectral features of both octasilacubane and octasilasecocubane were explained by the Si3p orbitals hybridized with Si3s and Si3d and C2p orbitals. © 2000 Elsevier Science B.V. All rights reserved.

Resonant elastic x-ray scattering (REXS) was observed at the carbon K threshold of graphite powder, and a small amount of excitonic x-ray scattering was observed in diamond. A comparison of the energy spectra of REXS in graphite with the carbon K x-ray absorption spectra, and with the calculated energy spectra of the unoccupied density of states, suggests that REXS is caused by the transition of the “participator” electrons via (Formula presented) states in (Formula presented)-carbon atoms. The probabilities of transition to “participator” REXS or to “spectator” resonant inelastic x-ray scattering in the resonant radiative-decay process of graphite powder, were determined from REXS spectroscopy to be approximately 47% and 53%, respectively. © 2000 The American Physical Society.

Benzene and pyridine molecules adsorbed in micropores of microporous carbon were directly observed by synchrotron-radiation-excited soft X-ray emission spectroscopy. There were spectral feature differences in C K X-ray emission between the adsorbate benzene and pyridine molecules, while the X-ray spectra agreed closely with their corresponding calculated C2p-DOS spectra. These results show that synchrotron-radiation-excited soft X-ray emission spectroscopy is a powerful tool for in-situ direct observation of molecular adsorbates in bulk microporous materials and for investigating their electronic structures and chemical bonding states in micropores.

The X-ray emission spectra of crystalline carbon nitride films deposited by elcctron-cyclotron-resonance (ECR) plasma sputtering were observed using a high-resolution soft X-ray spectrometer at the Advanced Light Source to investigate the electronic structure of carbon nitride crystals. The spectral features in C K and N K X-ray emissions from the ECR-deposilcd carbon nitride films represent the highly degenerated valence Orbitals and their highly pure crystalline form. The C K and N K X-ray emission spectra were approximately explained based on the C2p and N2p density of states in the hybridized C-N bonds. The absence of significant peak shifting in selectively excited C K and N A' X-ray emission spectra showed that there is a fairly nondispersive structure between valence and conduction bands in ECR-dcpositcd carbon nitride films. ©1999 Publication Board, Japanese Journal of Applied Physics.

L X-ray emission spectra in the energy region of the Cr 2p threshold on Cr compounds were measured and analysed using tunable synchrotron radiation. The X-ray absorption and emission spectra (XAES) of Cr (VI) are very different from those of Cr (III). It is considered that the difference in the soft X-ray emission is mainly attributed to the effect of the covalency in bonding, because the transition intensity of the Kβ2 spectral line is sensitive for the valence electronic configuration. Therefore, it follows that XAES is very sensitive to the ligand environment in Cr compounds and relatively insensitive to the metal oxidation state, as Grush et al. suggested for Mn complexes [J. Electron. Spectros. Relat. Phenom. 92 (1998) 225]. © 1999 Elsevier Science B.V. All rights reserved.

X-ray emission and absorption spectra of carbon nitride films prepared by laser ablation were measured. The carbon x-ray spectra of films obtained in a nitrogen atmosphere were different from those of a film prepared in vacuum. It was found from DV-Xα molecular orbital calculations on x-ray spectra that the films obtained in a nitrogen atmosphere contained bonding between carbon and nitrogen atoms. This was supported by the Fourier transform IR spectra. Copyright © 1999 John Wiley & Sons, Ltd.

The DV-Xα molecular orbital (MO) calculation method was applied to the B K-V x-ray emission spectra of hexagonal (h-)α, cubic (c-) and wurtzite (w-) type boron nitrides (BN). The calculated B 2p density of states (DOS) was in good agreement with the B K-V x-ray emission. The main peaks and low-energy satellite peaks in the B K-V x-ray emission spectra are due to the B 2p and the B 2p hybridized with N 2s, respectively. The high-energy satellite peak in the B K-V x-ray emission spectra clearly corresponds to the π* sub-band of the B 2p DOS in h-BN. However, the high-energy satellite peak observed in w-BN is not in agreement with the B 2p DOS. It is considered that the high-energy satellite peaks are due to less than four-coordinated B atoms such as have dangling bonds and defects in w-BN. In the B K-V x-ray emission spectra of h-BN, the synthesizing π and σ sub-bands of B 2p DOS could explain the polarized emission spectra very well. Copyright © 1999 John Wiley & Sons, Ltd.

The electronic structure and radiative/non-radiative decay processes in the inner-shell excitation of B2O3 were investigated using soft x-ray emission and photoelectron spectroscopy. Based on density of states calculations, the electronic structure of B2O3 as probed by x-ray emission spectroscopy (XES) and photoelectron spectroscopy (PES) arises from hybridized sp2-planar B - O bonding in B - O3 triangular units. A fairly non-dispersive band structure was also suggested by excitation energy-dependent XES. XES and PES indicated both a resonant radiative decay process and a resonant non-radiative decay process with π* excitation at the B K threshold. A small resonant radiative decay peak was observed with π* excitation at the O K threshold probably due to a more weakly bound π* state at the O K threshold than at the B K threshold. Copyright © 1999 John Wiley & Sons, Ltd.

Theoretical C K and N K X-ray emission/absorption spectra of fullerene-like-structured carbon nitride (C24N36) clusters were obtained using discrete-variational (DV)-Xα molecular orbital calculations. These calculations predicted that the energy widths of the C K and N K X-ray emission peaks would be about 8 and 6 eV, respectively; three low-energy satellites would appear in each emission spectrum; and there would be a narrow HOMO-LUMO energy gap of 0.38 eV. These theoretically predicted X-ray emission/absorption spectra will be useful in the synthesis and characterisation of fullerene-like carbon nitrides. © 1999 Elsevier Science B.V. All rights reserved.

In order to understand the function of transition metals, which are a necessary part of many catalytic cycles, it is necessary to obtain information about oxidation states, ligand environment, and local structure surrounding the metal centers. L-Edge X-ray absorption spectroscopy, which probes the unoccupied 3d levels, has been shown to be a sensitive probe of the oxidation and spin state of transition metal sites. As soft X-ray fluorescence (SXF) instead probes the occupied states, an investigation of how this complementary technique can be used to probe transition metal centers was conducted and the results are presented here. SXF is found to be very sensitive to ligand environment and relatively insensitive to electronic geometry and metal oxidation state. Potential applications of this technique to systems such as metalloproteins and manganese-lithium batteries are discussed. © 1998 Published by Elsevier Science B.V. All rights reserved.

Soft X-ray emission and absorption (SXEA) spectroscopy is presented as a possible method for electronic structure analysis. To demonstrate its feasibility, the electronic structure of silicon backbones in a cubic silicon cluster (octasilacubane) and its related clusters was analyzed by measuring the SXEA spectra in the Si K-shell threshold. Three discrete levels are observed in both Si3p occupied and unoccupied orbitals of octasilacubane, which may be caused by the large degree of degeneracy of the orbitals due to the high symmetry of the cubic silicon backbone structure. The measured narrow energy gap of 2.3 eV between the highest occupied and the lowest unoccupied orbitals of octasilacubane shows that Si3p σ-electrons in octasilacubane are more widely conjugated than those in the related clusters. © 1997 Elsevier Science B.V.

The boron Kα X-ray fluorescence spectra of TiB2, BP, B6O, and CaB6 were measured using undulator radiation with change in the primary X-ray energy. Variation of the resonance peak at 185-190 eV was observed with a change in the compound or in the incident X-ray energy. The modification of the resonance peak intensity was most pronounced when the excitation energy was the K edge threshold energy. © 1997 Elsevier Science B.V.

The B K X-ray emission spectrum of h-BN can be approximately reproduced by the DV-Xα calculation, using the two-dimensional model cluster constructed of a mono-layer of the planar hexagonal network. In order to verify the polarized B K X-ray emission spectrum of h-BN, the contributions of the σ, π and π* subbands to its spectral feature were estimated at different take-off angles for the c axis of an h-BN crystal. The high-energy satellite band increases its intensity, remarkably, due to the contribution of the π* subband with increase in take-off angle, whereas the low-energy satellite band decreases its intensity due to the contribution of the σ subband. The measured B K X-ray emission spectrum of the ion-plated h-BN thin film is in good agreement with the calculated one at a take-off angle of 90°.

We describe the application of resonant X-ray emissions for molecular/electronic structure analysis of boron nitrides using quasimonochromatic undulator radiation at the Photon Factory. Prominent resonant X-ray emissions due to B1s-B2pπ*-B1s-1 transitions were observed in w-BN composed of four-fold boron atoms and in h-BN composed of three-fold boron atoms, when the photon energy of the incident undulator beams coincided with the B1s-B2pπ* absorption energy. However, no resonance was observed in c-BN composed of four-fold boron atoms. The resonant X-ray emission reflects the electronic structure of unoccupied molecular orbitals which strongly depend on the conformnations of the boron atoms. These findings confirm that resonant X-ray emissions can be useful indices for molecular and electronic structure analysis of boron nitrides. © Springer-Verlag 1997.

The resonant soft-x-ray emission (SXE) and its total photon yield (TPY) spectra were measured at the B 1s and N 1s edges of cubic boron nitride (cBN) using undulator radiation. The band-gap energy was found to be about 6.2 eV, which is in good agreement with other experiments. It was found that the emission from the high symmetry point in the SXE spectrum is enhanced when the same high symmetry point in the TPY spectrum is excited. The line shapes in both the SXE and N 1s TPY spectra were consistent with the calculated partial density of states, though the total bandwidth was not well reproduced. On the other hand, the exciton effect was found to be strong in the B 1s TPY spectra. © 1997 The American Physical Society.

A system has been developed for realtime crystal-growth analysis by photoelectron spectroscopy, using vacuum ultraviolet (VUV) light from synchrotron radiation. This system consists of a VUV synchrotron radiation beamline and growth/analysis apparatus in which photoelectron spectroscopy is performed. A "non-scanning" photoelectron spectroscopy measurement method that uses only electron energy dispersion on a multi-channel detector achieves sub-second resolution. This system was used to monitor the GaSb-growth process by alternately supplying Ga and Sb molecular beams; the changes in the chemical state were analyzed with sub-second resolution. The Ga supply resulted in a Ga-full surface; Ga droplets formed on this surface, in which the Sb atoms remained lying on the Ga layer. The Sb supply did not change the ratio of Ga and Sb atoms at the surface from the initial value. These results show that, exposure to an Sb flux causes a crystal surface to once again become an Sb-rich surface although Ga droplets were previously formed during exposure to a Ga flux a GaSb surface was thus successfully grown.

Enhanced resonant x–ray emissions were observed from mechanically milled hexagonal boron nitride nanoclusters in boron K–shell excitation using quasimonochromatic undulator radiation. The resonant x–ray emission intensity increases with decrease in size of the milled clusters. Comparison of the measured x–ray emission spectra with the calculated spectra using the discrete–variational X α methods showed enhanced resonant x–ray emissions originate from the B1s–n*–B1s−1 electron transition, with n* an unoccupied nonbonding orbital of twofold–coordination boron atoms with dangling bonds. X–ray emissions excited to n* orbitals may be possible for detecting dangling bonds in nanoclusters. © 1996 The American Physical Society.

Boron 2p density of states are calculated and compared with X-ray fluorescence spectra of h-BN. The high energy satellite, which was assigned to resonance X-ray scattering peak, is found to be 1s electron scattered by nonbonding unoccupied orbitals. Thus it is concluded that the resonance peak intensity is a measure of the density of dangling bonds in a nanocrystal. © 1995.

The high-energy satellite structure in the B Kα x-ray emission spectrum of hexagonal boron nitride (h-BN) has been measured by threshold excitation methods. Prominent x-ray emission of the high-energy satellite peaks was observed when the excitation energy was tuned to the π*- and σ*- absorption peaks. The spectral profile of the scattered radiation was also similar to the absorption spectrum. Therefore, the origin of the high-energy satellites is found to be the unshifted resonant x-ray emission of B(1s) – (unoccupied anti-bonding π* and/or σ* orbitals) – B(1s−1) transition, which could be explained by the resonant x-ray Raman scattering. © 1994 IOP Publishing Ltd.

A VUV beamline (ABL-3B) for real-time photoelectron spectroscopy has been developed at the normal-conducting accelerating ring (NAR) of the NTT synchrotron radiation facility. To accept the incident synchrotron radiation beam with the wide horizontal divergence angle of 20 mrad, a 1.38-m-long cylindrically bent front mirror was devised. This mirror was composed of four plane mirror blocks connected together and mounted on a steel holder beam having a C-shaped cross section. The mirror holder can be bent by a novel bending device with a momentum of 1388 kg cm to achieve the optimum radius of the curvature of 63.9 m. The focused spot of 3.5 mm (H)×1.8 mm (V) was preliminarily obtained on the sample position by bending the front mirror. When the stored electron beam current was 50 mA and the "grasshopper" monochromator was tuned at 130 eV, a photon flux of 1.5×1010 photons/s was obtained with the energy resolution of 0.5 eV. © 1994.

An undulator-radiation-excited X-ray fluorescence analysis system has been developed at an undulator beamline of the Photon Factory. As an analytical application demonstrating the capabilities of this system, the chemical state of boron implanted with a high dosage of BF2+ into Si(100) was analyzed by measuring both the B Kα soft X-ray emission (SXE) and X-ray absorption near edge structure (XANES) with fluorescence detection. Comparing the SXE and fluorescence XANES spectra of B doped in Si with relevant reference boron compounds, it is confirmed that the chemical state of the B atoms as implanted in Si is metallic despite the fact that B is implanted as BF+2. Oxidation of B doped in Si by annealing at 900° C in atmosphere is also observed. © 1993.

X-ray emission spectra of buckminsterfullerene (C60) and alkali-metal fullerides (M3C60, where M denotes alkali-metal) are calculated with the discrete-variational (DV)-Xα method. The calculated x-ray emission spectra of C60 agree well with experimental x-ray spectra. This indicates that the x-ray emission spectrum of M3C60 calculated with the same method provides a good prediction of fulleride spectra which have not been measured yet. The calculated x-ray emission spectra are proposed to be used as standards of the electron probe microanalyzer (EPMA) spectra of fullerene and related compounds for searching the existence of such compounds in carbon mixtures. © 1993 American Institute of Physics.

The satellite structure for the B Kα emission spectrum of boron oxide has been elucidated by threshold experiments carried out by varying the excitation energy of the incident undulator beam from below the B K absorption edge to several tens of eV above the absorption edge. Priminent emission of the satellite peak was observed when the excitation energy was tuned to the narrow pre-edge peak in the absorption spectrum, corresponding to the transition from B (1s) to an unoccupied antibonding pπ* orbital. It is concluded that the satellite peak originates from resonant x-ray Raman scattering due to a B(1s)-pπ*-B(1s-1) transition. © 1993 The American Physical Society.

The relative stability of sulfur on (NH4)2S1 treated GaAs(111)B, 100 and (111)A surfaces has been determined and is given in the following order: (111)B > 100 > (111)A. These results are in accord with both theoretical calculations and the GaS coordination number for the three different surfaces. In addition, deposition of CaF2 on the sulfur treated GaAs surface followed with high temperature annealing results in a Ca2 to Ca0 reduction at the CaF2/S/GaAs interface, formation of islands as well as an increase in band bending. In contrast, deposition of GaF3 on S/GaAs results in band flattening. © 1992.

The interfacial chemical bonding has been investigated for GaF3 and CaF2 deposited on S passivated GaAs(111)A, 100, and (111)B surfaces. Synchrotron radiation excited photoelectron spectroscopy S 2p measurements indicate greater S surface segregation for the Ga terminated (111) A and (100) surfaces relative to the As terminated (111)B surface. This S surface segregation correlates well with the Ga - S bond strength as well as the S - Ga coordination number for the three different GaAs surfaces. X-ray photoelectron spectroscopy measurements indicate S may act as a catalyst in the reduction of Ca2+ to metallic Ca at the CaF2-S/GaAs(111)A interface. In contrast to island growth observed for the CaF2/S/GaAs system, more uniform growth is observed for the GaF3/S/GaAs system. In addition, in contrast to the CaF2/S/GaAs system, band bending is considerably reduced for all surfaces upon deposition and annealing for the GaF3/S/GaAs system.

SiC-based mechanically ruled master gratings and replicas are developed for synchrotron radiation instruments. An SiC-based gold replica grating without any thermal deformation due to active cooling is used in a high-photon-flux-soft x-ray monochromator that is installed in a bending magnet beamline. An SiC-based gold master grating is used in a vacuum ultraviolet/soft x-ray monochromator installed in an undulator beamline with slight groove shape deformation. This deformation is caused by the thermal change of the gold film occurring at higher than 250-300° C. A method for cleaning carbon-contaminated synchrotron radiation optics is tested. The ultraviolet ozone ashing method effectively cleans carbon contamination on the optics and is useful for extending the lifetime of synchrotron radiation optics.

Performance of a 2-m grazing incidence vacuum ultraviolet (VUV)/soft x-ray monochromator was evaluated with silicon-carbide-based master grating of 1200 lines/mm groove density that was newly developed for use of undulator radiation. Incident power density on the grating surface was as high as 120 mW/mm 2. Surface observation of the grating after the test operation showed that the periodic structure and reflective surface of the grooves were well preserved, except for slight degradation of the groove edges, even though no active cooling system was equipped. Photon flux was of the order of 10 12 photons/s. Efficiency of second-order diffraction relative to the first-order diffraction was 20%-50%. Resolving power of 2200 was achieved at 244.4 eV for 5-μm exit slit width.

An undulator-radiation-excited x-ray fluorescence analysis system for light elements has been developed and tested on the 26-period multipole wiggler/undulator beamline at the Photon Factory. An entrance-slitless optics with a variable-spacing grating was devised for a fluorescent x-ray dispersion system to achieve spectroscopic analysis with high efficiency and high resolution. Both soft x-ray emission (SXE) spectra and x-ray absorption near-edge structure (XANES) spectra with fluorescent x-ray detection were obtained by this system, taking advantage of the high brightness and quasimonochromatic character of the incident undulator beam. The analysis system was evaluated by measuring the B Kα SXE and fluorescence XANES spectra of B, BN, and B2O3.

The chemical bonding changes as a function of temperature in sulfur-passivated GaAs (111)A, (100), and (111)B surfaces were monitored in situ by synchrotron-radiation photoelectron spectroscopy. At relatively low temperatures (T200°C), As-S bonds are converted to Ga-S bonds. At higher temperatures, a well-ordered monolayer is observed and a predesorption state is observed for both the (111)A and (111)B surfaces at about 50°C below the S desorption temperature for the respective surfaces. It is also found that the S desorption temperature is well correlated with the coordination number of the sulfur atom on the GaAs surface. © 1991 The American Physical Society.

Design and experience of the initial operation of a new beamline (BL-16) for a 3.6-m-long, 53-pole wiggler/undulator constructed at the Photon Factory are described. The insertion device has hybrid permanent magnets with a period of 12 cm and a maximum magnetic field of 1.47 T. In the undulator mode, the energy of the fundamental peak can be varied from 40 to 400 eV. In the wiggler mode, an x-ray beam (critical energy of 6 keV) 50-100 times more intense than that from the bending magnets is obtained. The beamline consists of two time-shared branch lines: a side beamline for soft x-rays in the undulator operation, to which photon beams are deflected sideways by a cylindrical SiC mirror, and a straight line for hard x rays under the wiggler operation. On the hard x-ray line, a fixed-exit sagittal-focusing double-crystal monochromator has been installed and commissioned. Collimating and refocusing mirrors will be installed in 1989. On the undulator beamline, a soft x-ray monochromator utilizing sophisticatedly devised aberration correction optics is commissioned.

A curved Bragg reflector for focusing synchrotron radiation has been fabricated using a recently developed magnetron sputtering equipment. The Bragg reflector consists of alternate thin-film layers of W and C deposited on a cylindrical substrate of 46 mm in radius of curvature, covering a 50×50-mm2 area. The focusing properties of the Bragg reflector were examined at beamline 15B of the Photon Factory. The focused beam intensity per unit area was six times higher than the unfocused beam, and the observed variations in beam size and shape with optical distances showed qualitative agreement with ray-tracing calculations.