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The electronic structures of Gd-substituted Bi2−xGdxTe3 single crystals have been investigated by employing synchrotron-radiation spectroscopies, such as soft X-ray absorption spectroscopy (XAS), soft X-ray magnetic circular dichroism (XMCD), photoemission spectroscopy (PES), and scanning photoelectron microscopy (SPEM). SPEM measurements confirm that Gd ions are substituted homogeneously in Bi2−xGdxTe3 crystals. The measured Gd 3d XAS and XMCD spectra provide evidence that the substituted Gd ions are trivalent and magnetic. The hν-dependence of the valence-band (VB) PES spectra are described well by the hν-dependent contributions of the Te 5p and Bi 6p states. A good agreement is found between the measured VB PES spectra of Bi2−xGdxTe3 and the calculated partial densities of states, revealing that the Te 5p states will play an important role in determining the thermoelectric and topological properties of Bi2−xGdxTe3.

Kaolinite : defect states define material properties-a soft x-ray and first principles study of the band gap

Instrumentation and current capabilities of soft X-ray (50–2000 eV) spectromicroscopy are outlined with examples from recently published and some new work. Four common techniques are treated—transmission X-ray microscopy (TXM), scanning transmission X-ray microscopy (STXM), X-ray photoemission electron microscopy (XPEEM) and scanning photoemission microscopy (SPEM). I also present a fifth, emerging technique, that of soft X-ray spectro-ptychography which has significantly improved spatial resolution and provides new contrast mechanisms. Perspectives for near future (5–10 years) evolution of soft X-ray spectromicroscopy are outlined based on current trends and instrumentation under development.

We explored the possibility to quantify the atomic in-depth distributions by using the energy-dependent soft X-ray reflectivity (SXRR) measurements, in particular, the possibility to obtain the profiles of low- Z elements [C, N, O, Si] in heterostructures containing high concentration of higher- Z atoms [Ti, Sr, Hf]. We have shown that the SXRR technique allows one not only to quantify the atomic composition of the Sr-rich SrTi x O y insulators grown on (1 0 0)Si by the Atomic Layer Deposition method but also to obtain atomic profiles across a few-nm thick underlayer (UL) inserted between SrTi x O y film and the Si substrate. The accuracy of atomic concentrations and densities estimated is already sufficient to trace even small variations in composition of the SrTi x O y grown by ALD on the chemically different underlayers and most it is important the composition and extension of an interfaces.

Resonant inelastic X-ray scattering (RIXS) has emerged as a powerful method for the study of the electronic structure of matter in various phases and ambient conditions. The selectivity offered by ...

The brilliance of modern synchrotron radiation sources and capabilities of new instrumentation facilitate resonant inelastic soft X-ray scattering of liquids and molecular materials with high spect ...

Nanostructured samples of yttrium iron garnet Y 3 Fe 5 O 12 obtained by plastic deformation method (high-pressure torsion) were studied with help of soft X-ray absorption spectroscopy using Fe 2 p and O 1 s spectra. Experimental spectra were compared with crystal field multiplet calculations for Fe ions. Some amount of Fe 2+ ions in nanostructured Y 3 Fe 5 O 12 was found. The concentration of Fe 2+ ions was found to be increased with the increase of the degree of plastic deformation.

In this paper we present the first core-level photoelectron spectroscopic study of solid nanoparticles in liquid water. The particles are SiO(2)-based with an average diameter of 70 nm and function ...

We have developed a 25 T pulsed high magnetic field system for soft X-ray Magnetic Circular Dichroism: XMCD. The ultra-high vacuum chamber with a pulse magnet coil is installed. By using a newly developed bipolar capacitor bank, the XMCD of paramagnetic Gd2O3 at the M5 and the M4 edges was clearly observed at low temperatures. The present system is capable of measuring XMCD of field induced moments in various compounds including paramagnets and antiferromagnets.

The beam-induced effects, a consequence of the high photon flux density used in soft X-ray photoelectron emission microscopes in operation at the 3rd generation synchrotron sources, are discussed and illustrated using some representative results obtained with the microscopes at the laboratory Elettra. The focus is on the photon-induced charge potential and chemical degradation, which might be a severe problem for photon-sensible specimens. The possible steps to avoid, reduce or even make use of the beam-induced effects are outlined.

We report soft X-ray total ion yield and angular-resolved ion yield spectra of CF3I in the C 1s, I 3d and F 1s ionisation regions, and tentatively assign the observed electronic states. Anisotropy in ion yield is observed only for the C 1 s → σ C – I ∗ transition, indicating that the dipole moment for this transition is parallel to the C3v. The effusive source of CF3I is heated to 800 K to produce a mixture of CF3 and I, and the resulting spectra are compared to those recorded at room temperature.

We present L2,3 X-ray emission spectra of the 3d-metals Ti through Cu. It is found that the ratio of the integrated non-resonant emission intensities of L2 to L3 emission, I(L2)/I(L3), is approximately two times smaller than the ratio of the core hole state degeneracies (L2/L3 = 1/2). Our atomic calculations show that the L2L3M4,5 Coster–Kronig transition is responsible for the reduction of the I(L2)/I(L3) intensity ratio and explains its gradual decrease with increasing atomic number among the 3d transition metals. For the resonant case we find that accounting for the core–hole interaction and local field effects via TDDFT satisfactorily explains the changes in the I(L2)/I(L3) ratio.

The intensity of the La 5p → 4d emission of La metal is being monitored while scanning across the deeper-lying 3d → 4f photoexcitation thresholds of the same atom. We find a strong resonant enhancement in the La 5p–4d fluorescence emission (around 83 eV) when exciting at the 3d → 4f resonances (829–852 eV). We show that the emission behavior is due to cascading decay of the resonantly excited 3d94f+1 configuration. The number of 4d-vacancies increases immensely due to electronic cascades. By calculating the probability of the 5p → 4d emission resulting from cascading decay and then taking into account self-absorption of the emitted photons, we obtain good agreement with the experimental results. We also report an enhanced integral intensity in the 5p → 4d fluorescence, which we attribute to intra-atomic resonance processes.

We report the soft-X-ray absorption and emission studies of NaCl, MgCl2, and AlCl3 in water solutions. The influences of cations on the water molecular structure can be seen as the absorption threshold edge shifted to high energy in the X-ray absorption spectra; the mixing of molecular orbital in 3a1 symmetry is reinforced as the intensity of 3a1 is further reduced; and the 1b1-emission peak shows the broadening and shift differently for Na+, Mg2+, and Al3+ water solutions, which indicates that the charge difference of the cations may not be the only playing role being responsible to the interactions between the cations and water molecules.

The photoexcited F K α X-ray intensity’s evolution was measured for CaF2 with fine energy-step from the [1s2p] double excitation threshold to the saturation region, where square brackets indicate hole states. The observed evolution was directly compared with the X-ray absorption spectrum, and the contribution of multielectron excitation to the absorption spectrum was successfully resolved. The F-K fluorescence XANES spectra were calculated based on the coherent second-order optical processes for comparison.

The electronic structure of doped Mott-insulator La 1− x Sr x TiO 3 has been studied by resonant soft-X-ray emission spectroscopy (SXES). The Raman scattering of the e g - and t 2g -resonant SXES spectra indicates features due to the d–d transitions corresponding to the crystal field splitting (10Dq) and half on-site Coulomb energy ( U dd /2), respectively. The U dd does not change much around two metal–insulator transitions at x = 0.05 and 0.95 in La 1− x Sr x TiO 3 , while the 10Dq increases as a function of x . These results are in good agreement with the prediction of dynamical mean field theory calculation.

The molecular structure of alcohol-water mixtures determined by soft-X-ray absorption and emission spectroscopy

High-energy angle-resolved photoemission spectroscopy (ARPES) for investigating valence-band dispersions has become feasible by virtue of improvements in both synchrotron light source and photoelectron spectrometer. We report very recent progress in the high-energy ARPES and several high-energy ARPES data on strongly correlated systems. We also refer to a higher-energy X-ray photoemission study of a rare-earth compound.

Resonant inverse photoemission spectroscopy (RIPES) measurements have been performed in the soft X-ray (SX) region. The energy region, which could not be accessible up to these days, includes core levels of many important elements to be investigated. They were applied to transition metals (TM), rare earth (RE) metals, and their compounds. Remarkable resonance enhancement was observed in Ce 4d→4f resonance of some Ce compounds. This gives us complementary information with Ce 3d resonance IPES that was reported before. 2p and 3p resonance spectra were observed for the TM compounds. These resonances show rather weak enhancement compared with those of Ce compounds, although apparent resonance feature was observed. These results are well-reproduced by many-body configuration interaction on the basis of the Anderson impurity model. Though the study has just started, the results demonstrated the effectiveness of the RIPES measurements.

Absolute UV and VUV photoabsorption oscillator strengths (cross sections) for the valence shell discrete and continuum regions of benzene (C 6 H 6 ) have been measured from 4 to 56 eV using high resolution (∼0.05 eV fwhm) dipole (e,e) spectroscopy. A wide-range spectrum, spanning the UV, VUV and soft X-ray regions, from 5 to 200 eV has also been obtained at low resolution (∼1 eV fwhm), and this has been used to determine the absolute oscillator strength scale by employing valence shell TRK [i.e., S(0)] sum-rule normalization. The presently reported high and low resolution absolute photoabsorption oscillator strengths are compared with previously published data from direct photoabsorption measurements in those limited energy regions where such data are available. Evaluation of the S(−2) sum using the presently reported absolute differential photoabsorption oscillator strength data gives a static dipole polarizability for benzene in good agreement (within ∼3.4%) with published polarizability values obtained from optical measurements. Other dipole sums S( u ), ( u =−1, −3, −4, −5, −6, −8, −10), and logarithmic dipole sums L( u ), ( u =−1 to −6), are also determined from the presently reported absolute differential photoabsorption oscillator strength data using dipole sum-rules.

We have measured the temperature dependence of MCD spectra on Ce@C82 and Ce2@C80 in the Ce 3d–4f excitation region. The results show that Ce@C82 has antiferromagnetic interaction while Ce2@C80 has ferromagnetic interaction between Ce magnetic moments which are much smaller than the Hund-ground-state values.

Using Co L 2,3 resonant soft X-ray scattering measurement, we reveal that the magnetic orderings with q = (1/2, 0, 1/2) and (1/2, 0, 1) originate from different magnetic domains. Temperature dependence of the magnetic ordering peaks clearly shows that there is a finite difference between the transition temperatures of these magnetic orderings.

We review the current status of resonant inelastic soft X-ray scattering in broad band solids. In particular, the opportunities and limitations of this technique in order to obtain band structure information are discussed and compared to the well established technique of angle resolved photoemission.

Holographic gratings recorded with aspheric wave fronts have been designed by means of the analytic design method so as to have the interchangeability with mechanically ruled varied-line-space (VLS) gratings that were designed for soft X-ray flat-field spectrographs. It is shown that aspheric wave-front recording optics makes it possible to produce large variations in the grating constant (e.g., more than 30% over a ruled area of 50 mm) required for flat-field spectrographs. The imaging properties of the holographic gratings thus designed are discussed from the viewpoint of interchangeability with mechanically ruled VLS gratings.

We have carried out soft and hard X-ray spectroscopy of Sm-based filled skutterudites SmFe 4 P 12 and SmOs 4 Sb 12 . Sm 3d–4f resonant photoemission and Sm 3d–4f X-ray absorption spectra suggest that SmOs 4 Sb 12 has much more strongly mixed Sm valence state than SmFe 4 P 12 in the bulk. On the other hand, the Sm trivalent state is dominant on the surface of SmOs 4 Sb 12 .

We present experimental data on the resonant inelastic soft X-ray scattering at the Si L 3 edge in crystalline silicon. The experimental results are compared with scattering calculations based on LCAO and KKR band-structure calculations. We discuss the origin of the spectral features including the role of Si d-states in the scattering. q 1998 Elsevier Science B.V. All rights reserved

At the beamline BL8B1, UVSOR, the polarization diagnosis was performed with an ellipsometric method using a so-called rotating analyzer mounted with a reflection multilayer. The performance of a free-standing Al/YB6 transmission multilayer was studied using linearly and circularly polarized light obtained by selecting the angle of observation. The polarizance and the phase retardation of the multilayer for monochromatized light at 65 eV were 92% and 68° at their maxima in the angle of incidence response, respectively. It has been shown that the polarization of synchrotron radiation in the soft X-ray region can be transformed into linear and circular polarization by use of the transmission multilayers.

SiC/Mg multilayer mirrors were fabricated by magnetron sputtering for use in extreme ultraviolet photoelectron microscopy, applications of soft X-rays with high-order harmonics, astronomy and other applications for the wavelength region around 30 nm. They were found to have a peak reflectivity of over 40% at a wavelength of 30 nm and near normal incidence. The reflectivity remained constant up to a temperature of 300 °C after annealing for 1 h in an Ar atmosphere.

We carried out the full polarization measurements on highly circularly polarized light in soft X-ray region. The measurements were performed on synchrotron radiation of near 400 eV emitted from twin helical undulators at BL25SU in the SPring-8. All parameters of polarization state of the light were determined with a phase shifting transmission multilayer and a polarizing reflection multilayer. The phase shifter was a newly developed Sc/Cr multilayer and was evaluated as a quarter-wave plate. The results of full polarization measurement indicated that the twin undulators produced symmetrically circularly polarized light.

We observed the natural circular dichroism NCD of amino acid films in the soft X-ray region for the first time [M. Tanaka, K. Nakagawa, A. Agui, K. Fujii, A. Yokoya, Physica Scripta, in press]. Based on the success, a new generation of detection system is now under preparation. Vacuum ultraviolet NCD of amino acid films was measured successfully using a polarizing undulator [H. Onuki, Nucl. Instrum. Meth. A 246 (1986) 94] installed at the TERAS electron storage ring at AIST, Tsukuba, Japan. A result of NCD measurement for alanine films is described in detail.

To perform the accurate full polarization measurement in soft X-ray region, we designed and fabricated a quarter-wave plate using a transmission type Sc/Cr multilayer. The phase shifter showed −0.19 polarizance and 0.4% transmittance for 90° retardation.

Absolute intensities of monochromatized soft X-rays from the synchrotron radiation source were measured sequentially using both a cryogenic radiometer and a multi-electrode ion chamber at a photon energy of 150.4 eV. The absolute intensities obtained by these methods were mutually compared to check reliability for the different measuring methods and agreed with each other within the uncertainty of about 10%.

The soft x-ray scanning photoelectron microscope has been developed and installed at a soft x-ray beamline of the Photon Factory (KEK-PF). The microscope uses a Wolter type-I grazing incidence mirror to form a soft x-ray microbeam. The mirror was fabricated more accurately than previous one by using a new replication method, allowing a 0.47-μm microbeam to be ahcieved. In addition, a high-precision x-y sample stage made it possible to obtain two dimensional photoelectron images. The microscope demonstrated a total-photoyield image of 0.3-μm-linewidth stripe patterns and an energy-selected photoelectron image of 2-μm-linewidth stripe patterns.

The Ti2p and O1s soft X-ray emission spectra were measured on rutile (TiO2) for the energy region of Ti2p and O1s excitation threshold. The ordinary fluorescence spectra resolve the Ti3d and O2p components in the valence bands. An elastic scattering peak is observed and resonantly enhanced at excitation energies corresponding to Ti2p absorption peaks. Furthermore, an inelastic scattering peak is observed. The peak is assumed to be caused by an elementary excitation that is charge transfer excitation from O2p valence band to Ti3d conduction band.

A soft X-ray microscope was constructed using grazing incidence mirrors and a laser-produced plasma source. A Q-switched Nd-YAG laser (1.064μm, 530mJ, 6ns pulse) and a Wolter type-I mirror objective were used. The spatial resolution estimated by the edge profile (25% – 75%) was about 60nm using 5 – 7nm soft X-rays from an Al target. Hydrated biological specimens, such as human blood cells, could be observed using an environmental chamber with Si 3 N 4 windows (thickness: 0.1μm), a back-illuminated CCD camera, and 3–5nm soft X-rays from a Ta target.

The evaluation of reflectivity measurements is a powerful method to determine the optical constants of materials. We present data obtained from SiO 2 in the soft x-ray region (50–900 eV). The results of two different evaluation techniques — the Kramers-Kronig analysis of energy dependent measurements and the analysis of angular dependent reflectivity spectra — are compared with the data obtained from atomic scattering factors.

The effects of heating on both the reflectivity and layered structures of Mo/Si and Mo/C/Si/C multilayers were evaluated. The CuK α x-ray reflectivity and periodic length of the Mo/Si multilayer markedly decreased after heating at above 300°C, while those of the Mo/C/Si/C multilayers changed only slightly even after heating at up to 700°C. Transmission electron microscopy observations revealed markedly less thermally induced deterioration in the Mo/C/Si/C multilayers than in Mo/Si multilayer, indicating that Mo/C/Si/C multilayers have better heat resistance than Mo/S multilayer.

In recent years much progress has been made in the field of spectromicroscopy, the combination of spectroscopy with lateral resolution. This method is applicated increasingly to problems in biology, material and surface science. Different technical approaches will be outlined and discussed with respect to their imaging and spectroscopic properties. The scanning soft x-ray microscope at HASYLAB has been equipped continuously with new operating modes and has now the capability to use photoelectrons, photodesorbed ions, luminescence, fluorescence, scattered and transmitted photons for imaging and spectroscopy. Examinations of artificial structures, of luminescent ceramics and crystals and of porous silicon will be presented.

Soft x-ray microscopes offer higher resolution than confocM optical microscopes, and unique contrast characteristics which are well suited to the study of biological and materials science samples. A number of such microscopes are in use worldwide (see e.g., [1]). We describe here a scanning transmission microscope which operates at the National Synchrotron Light Source at Brookhaven National Laboratory. The microscope is used in large part for studies of biological specimens, and plans for cryo microscopy and development of higher resolution zone plate optics are described.

Recent performances of the soft X-ray crystal monochromator stations with new mirrors at the Photon Factory are described. About 10 11 photons/s of 2–4 keV in a spot of about 1 mm × 1 mm are now available with a high resolution (E/ΔE5000) at the undulator station BL-2A. While the dipole-magnet station BL-11B is suitable for EXAFS measurements on Si, P, S, and Cl K-edges, where the reflectivity and stability of the first mirror have been improved.

We have determined the absorption coefficients of several rare earths (Gd, Dy, Ho and Er) at the M4,5 edges (3d → 4f excitations) by measuring the soft X-ray transmission through layers of different thicknesses between 2 and 400 A. Our results are in good agreement with atomic calculations. We also compare transmission-derived absorption curves with spectra collected simultaneously in the standard total electron yield mode. Advantages and limitations of the transmission mode for soft X-rays and also its range of application are discussed.

A new soft X-ray source exploiting the Zr MζX-ray transition at h ν = 151.6 eV is described. This source yields core level and valence band photoemission spectroscopy with high sensitivity to the surface and to valence s- and p-derived states with respect to the d-derived states. An in situ cleaning procedure of the anode surface yields a resolution of 1.05 eV full width at half maximum.

Progress in the commissioning of the new soft X-ray beamline 11A at the Photon Factory is reported. Highly pure soft X-rays down from 70 up to 1900 eV were found to be obtainable with two holographically recorded varied-line-spacing gratings and a novel harmonic-rejection double-mirror system. The wide photon energy availability is quite useful to measure EXAFS spectra on B, C, N, O, F, Na, Mg, or Al K-edge.

A study of the coloration of glass surfaces induced by soft X-rays was made using X-ray photoelectron spectroscopy and optical absorption measurements. Sodium was found to be the dominant metal impurity in the glass that exhibits the surface coloration. An analysis of the relative atomic concentration of the impurity shows an increase of sodium with increasing exposure of the glass surface to the soft X-rays. The results suggest that the color-center sites involve trapped photoelectrons near the surface region, which can cause mobile sodium ions to move toward the exposed glass surface.

The angular distribution of photoelectrons ejected from the 2p shell in neon was investigated, for the first time, in the soft x-ray region, using a do

Simple models for the energy displacement between Wentzel-Druyvesteyn satellites and main lines in soft X-ray emission spectra of molecules are presented. The models include effective hole-hole interaction parameters and are evaluated numerically for H 2 O.

Recent theoretical studies have aroused interest in the phonon broadening of the soft x-ray emission and absorption edges and the shift between them. Using a self-absorption technique a separation of about 0.2 eV is shown to exist between the edges in Be metal. This shift explains the very small self-absorption effects previously observed in Be by Crisp (Ref. 1).