bluuebunny/crossref_metadata_2025 huggingface dataset:
AB INITIO CALCULATIONS OF THE MAGNETO-OPTICAL RESPONSE OF LAYERED SYSTEMS
Authors: EBERT HUBERT , PERLOV ALEXANDER , HUHNE TILMANN
Published: October 2002

The concept of the layer-resolved optical conductivity [Formula: see text] applied by means of a conventional band structure method is introduced. It is demonstrated that it allows a detailed discussion of the magneto-optical properties of magnetic multilayer systems. In particular it is found that the layer-projected optical conductivity [Formula: see text] of an atomic layer is influenced by only very few neighboring layers. This property can be exploited within the Baukasten principle, which aims to predict the magneto-optical properties of a complex layer system from the properties calculated for a closely related but simpler one.
ELECTRON CORRELATION EFFECTS IN HALF-METALLIC TRANSITION METAL OXIDES
Authors: HUANG D. J. , TJENG L. H. , CHEN J. , CHANG C. F. , WU W. P. , RATA A. D. , HIBMA T. , CHUNG S. C. , SHYU S.-G. , WU C.-C. , CHEN C. T.
Published: October 2002

Spin-resolved photoemission and absorption studies of Fe 3 O 4 and CrO 2 epitaxial thin films have been reviewed to address the relationship between the electron correlation effects and the half-metallic properties of these two materials. Spin-resolved photoemission results suggest that Fe 3 O 4 should be considered as a strongly correlated system, and that Fe 3 O 4 is not a half-metal. Spin-resolved O 1s X-ray absorption measurements on ferromagnetic CrO 2 reveal that the spin polarization of the unoccupied states closest to the Fermi level approaches 100%, confirming the half-metallic ferromagnetic nature of the material. The spin polarization of the main line of the unoccupied states, on the other hand, is found to be only 50%, indicating a very atomic-like behavior of the Cr 3d2 ions.
COMPUTED TOMOGRAPHY OF CRYOGENIC CELLS
Authors: SCHNEIDER G. , ANDERSON E. , VOGT S. , KNÖCHEL C. , WEISS D. , LEGROS M. , LARABELL C.
Published: October 2002

Soft X-ray microscopy has resolved 30 nm structures in biological cells. To protect the cells from radiation damage caused by X-rays, imaging of the samples has to be performed at cryogenic temperatures, which makes it possible to take multiple images of a single cell. Due to the small numerical aperture of zone plates, X-ray objectives have a depth of focus on the order of several microns. By treating the X-ray microscopic images as projections of the sample absorption, computed tomography (CT) can be performed. Since cryogenic biological samples are resistant to radiation damage, it is possible to reconstruct frozen-hydrated cells imaged with a full-field X-ray microscope. This approach is used to obtain three-dimensional information about the location of specific proteins in cells. To localize proteins in cells, immunolabeling with strongly X-ray absorbing nanoparticles was performed. With the new tomography setup developed for the X-ray microscope XM-1 installed at the ALS, we have performed tomography of immunolabeled frozen-hydrated cells to detect protein distributions inside of cells. As a first example, the distribution of the nuclear protein male-specific lethal 1 (MSL-1) in the Drosophila melanogaster cell was studied.
PHOTON YIELD FROM SOLID KRYPTON AND XENON AT THE EDGE OF EXCITON ABSORPTION
Authors: OGURTSOV A. N. , SAVCHENKO E. V. , GMINDER E. , VIELHAUER S. , ZIMMERER G.
Published: October 2002

The spectra of photon yield from solid Xe and Kr were measured in the energy range of absorption of Γ(3/2) n = 1 excitons. Using combination of time-resolved spectroscopy with selective photoexcitation by synchrotron radiation, the creation of free excitons was experimentally separated from direct population of molecular emitting centers. For the first time the threshold of photon absorption by molecular trapped centers is observed in excitation spectra of free exciton luminescence.
RESONANT AUGER DECAY OF Xe3d-16p TO Xe+4d-2np
Authors: DE FANIS ALBERTO , UEDA KIYOSHI , SAITO NORIO , KITAJIMA MASASHI , TANAKA HIROSHI , SHIMIZU YUICHIRO , OKADA KAZUMASA , KOYANO INOSUKE
Published: October 2002

Angle-resolved resonant Auger spectra for the transitions Xe [Formula: see text] are recorded with optical and electron energy bandwidths smaller than the lifetime widths Γ of the Auger initial and final states. All the multiplet structures are resolved for the ionic core 4d -2 of the spectator Auger final states and assigned as 4d -21 S 0n p , 1 D 2n p , 1 G 4n p , 3 P 0, 1, 2n p and 3 F 1, 2, 3n p , n = 6, 7, by comparison with previous measurements and calculations for the corresponding normal Auger emission. The resonant Auger anisotropy parameters obtained from the angular distribution measurements agree well with those expected from the spectator model.
BENT AND LINEAR GEOMETRIES OF RENNER–TELLER PAIR STATES IN CO2 PROBED BY TRIPLE-ION-COINCIDENCE MOMENTUM IMAGING
Authors: MURAMATSU Y. , UEDA K. , CHIBA H. , SAITO N. , LAVOLLÉE M. , CZASCH A. , WEBER T. , JAGUTZKI O. , SCHMIDT-BÖCKING H. , MOSHAMMER R. , KUBOZUKA K. , KOYANO I.
Published: October 2002

The C 1s-12πu1Πu state of a linear molecule CO 2 splits into two states. The lower state becomes bent and the upper state remains linear. As a direct probe of this Renner–Teller effect, the bent and linear geometries of the Renner–Teller pair states have been probed by means of triple-ion-coincidence momentum imaging.
X-RAY ABSORPTION SPECTRA OF SOME SMALL POLYATOMIC MOLECULES
Authors: PRINCE K. C. , RICHTER R. , DE SIMONE M. , CORENO M.
Published: October 2002

We report the Near Edge X-ray Absorption Fine Structure Spectra (NEXAFS) of a series of oxygen-containing organic molecules, namely formaldehyde, acetaldehyde, acetone, formic acid, methanol and dimethyl ether (DME), measured with high resolution at the carbon and oxygen edges. A vibrational progression has been observed at the oxygen 1s → π* resonance of formaldehyde, indicating that this state is bound with an excited state C=O stretching frequency of 136 meV. The spectra are compared with previous measurements and the applicability of the chromophore concept is tested for the functional groups present in these molecules.
NON-FRANCK–CONDON EFFECTS IN THE PHOTOIONIZATION OF N2 TO THE ${\rm N}_2^+$ A 2Πu STATE AND OF O2 TO THE ${\rm O}_2^+$ X 2Πg STATE IN THE 19–34 eV PHOTON ENERGY REGION
Authors: RIUS I RIU J. , ÁLVAREZ J. , KARAWAJCZYK A. , STANKIEWICZ M. , WINIARCZYK P. , VESETH L.
Published: October 2002

Photoionization to the [Formula: see text] A 2Πu state and to the [Formula: see text] X 2Πg state is studied using photoelectron spectroscopy. The experimental vibrational branching ratios are obtained for the first time in the 19–34 eV region for the v′ = 0–3 levels, for both molecules. Ab initio many-body perturbation theory is used to calculate branching ratios for ionization to the [Formula: see text] A 2Πu state and branching ratios, vibrationally resolved partial cross sections and total cross section for ionization to the [Formula: see text] X 2Πg state. The Franck–Condon breakdown observed in the photoionization of the N 2 1πu electron is mainly explained by autoionization from Rydberg and valence states of N 2, whereas photoionization of the O 2πg electron is not fully explained either by channel coupling effects or by autoionization from known Rydberg series and valence states.
SELECTIVE FRAGMENTATION OF VALENCE- AND CORE-ELECTRON-EXCITED CD4 and SF6 MOLECULES
Authors: STANKIEWICZ M. , WINIARCZYK P. , RIUS I RIU J. , ÁLVAREZ J. , ERMAN P. , KARAWAJCZYK A. , RACHLEW E. , KUKK E. , HUTTULA M. , HATHERLY P.
Published: October 2002

Electron–ion coincidence measurements with energy-resolved electrons are a powerful tool in studies of molecular fragmentation processes, since fragmentation from a specific doorway state can be monitored while the remaining reactions are discriminated. Presently, we have applied this technique in measurements of coincidence spectra of the CD 4 and SF 6 molecules after valence and core electron excitation. The newly constructed energy-resolved electron–ion coincidence station developed for this project has been used. Our results on CD 4 are the first demonstration of a correlation between vibrations and molecular dissociation observed in this molecule. The SF 6 spectra reveal strong selectivity in dissociation following distinct electronic states of the molecule. This selectivity reflects the bonding properties of the potential surfaces involved in the studied processes. The obtained results exemplify the potential of the new multicoincidence station used in this work.
ELECTRONIC ENERGY DISSIPATION PROCESSES IN DOPED RARE GAS CLUSTERS WITH A SHELL-LIKE STRUCTURE
Authors: LAARMANN T. , VON HAEFTEN K. , WABNITZ H. , MÖLLER T.
Published: October 2002

Energy relaxation processes of photoexcited Ar M clusters (M < 50) covered with a shell of Kr atoms (up to 30 atoms) which are embedded in large Ne N clusters (N = 3500) are investigated with energy-resolved fluorescence spectroscopy. In the energy range of the Ne cluster absorption (16.5–18 eV) a strong energy transfer to the embedded Ar subcluster is observed, which results in desorption of electronically excited Ar * atoms. Ar * move through the Ne cluster, desorb and emit visible and near-infrared light in the vacuum ( 4p → 4s ). By coating the Ar clusters with Kr atoms, the Ar lines disappear and 5p → 5s transitions of Kr become dominant. Additionally, new bands occur, which are assigned to transitions of perturbed atomic Ar 4p states inside Ne clusters. A simple kinematic model is suggested to describe the suppression of desorption of excited Ar atoms from Ne clusters.
FRAGMENT-ION DESORPTION FROM SULFUR-CONTAINING AMINO ACIDS BY LOCALIZED CORE-LEVEL EXCITATION
Authors: BABA YUJI , SEKIGUCHI TETSUHIRO , SHIMOYAMA IWAO
Published: October 2002

The desorption of fragment ions from sulfur-containing amino acids following the sulfur K-edge photoexcitation has been investigated using monochromatized synchrotron radiation. The samples investigated are pellets of neutral L-cystine, L-cysteine and L-methionine. It was found that only atomic S+ ions are desorbed following the S 1s → σ* resonant excitations, while various kinds of molecular fragment ions containing carbon, nitrogen and oxygen atoms are desorbed by the low-energy electron irradiation. The photon-energy dependencies of the S + yields approximately resemble those of the total electron yields (TEY's). On the other hand, the edge-jump ratios, defined as I on /I off , where I on is the intensity at the core-to-valence resonance energy and I off is that at off-resonance energy, for the S +-yield curves are by more than ten times higher than those of the corresponding TEY curves. The edge-jump ratios and the partial electron yield spectra revealed that the low-energy electrons produced following the Auger decays scarcely contribute to the ion desorption. Also, it was elucidated that the S * desorption is induced by the direct core-to-valence excitation which is followed by the S KLL Auger decay. It was concluded that the core-to-valence resonant photoexcitation and succeeding specific S–S and S–C bond scissions play a major role in the ionic fragmentation in the present amino acids.
SOFT X-RAY ABSORPTION SPECTRA IN THE 0 K REGION OF MICROPOROUS CARBON AND SOME REFERENCE AROMATIC COMPOUNDS
Authors: MURAMATSU YASUJI , KURAMOTO KENTARO , GULLIKSON ERIC M. , PERERA RUPERT C. C.
Published: October 2002

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.
Cu CONTAMINANT REMOVAL USING UV/O3 AND REMOTE HYDROGEN PLASMA
Authors: CHOI KYUNSUK , HONG KWANG PYO , LEE CHONGMU
Published: October 2002

Removal of Cu contaminants from Si wafer was carried out using remote hydrogen plasma (RHP) and UV/O 3 cleaning techniques. The concentration of Cu impurities on the wafer surface was monitored by TXRF (total reflection X-ray fluorescence) and XPS (X-ray photoelectron spectroscopy). Our results show that Cu impurities can be effectively removed by hydrogen plasma and UV/O 3 cleaning techniques, if it is performed under optimum process conditions. The optimum process parameters for the remote hydrogen plasma cleaning are the rf power of 20 W and the exposure time of 5 min. The optimum exposure time of the UV/O 3 cleaning for Cu impurity removal is 1 min. A two-step cleaning process composed of remote hydrogen plasma cleaning first and UV/O 3 cleaning next has been found to be more effective than a single UV/O 3 cleaning process, a single remote hydrogen plasma cleaning process, or a two-step cleaning process composed of UV/O 3 cleaning first and remote hydrogen plasma cleaning next. Cleaning efficiency is maximized at optimum process conditions where Cu contaminant removal effect and recontamination effect are traded off. Increasing the process parameters higher than the optimum values would decrease the cleaning efficiency.
PEEM AND SXES CHARACTERIZATION ON THE SURFACE AND INTERFACE OF THE TRANSITION-METAL/SiC SYSTEM
Authors: LABIS JOSELITO , OHI AKIHIKO , KAMEZAWA CHIHIRO , FUJIKI TOSHINORI , YOSHIDA KENICHI , HIRAI MASAAKI , KUSAKA MASAHIKO , IWAMI MOTOHIRO
Published: October 2002

The Si L2,3 and C K soft X-ray emission spectra of the interface of the Ti(50 nm)/4H-SiC(substrate) system, thermally annealed from 800°C to 1000°C and characterized by soft X-ray emission spectroscopy (SXES), revealed the formation of a reacted region composed of silicides with Ti 5 Si 3 as the majority formed species and carbides in TiC-like bonding. Also, the photoemission electron microscopy (PEEM) imaging of Ti(10 nm) film on 3C-SiC surface during in situ heat treatment showed the formation of island structures (in ring clusters) at ~ 800°C.
THE DYNAMICS PROPERTIES ON LUMINESCENCE OF CeF3 CRYSTALS
Authors: SHI CHAOSHU , ZHANG GUOBIN , WEI YAGUANG , HAN ZHENGFU , SHI JUNYAN , HU GUANQIN , KIRM M. , ZIMMERER G.
Published: October 2002

This paper presents temperature dependence of emission spectra (290 nm and 340 nm bands), excitation spectra (250–3000 Å), luminescence decay time as well as their excitation effect for CeF 3 crystals. The results indicate that energy transfer from Ce 3+ to defect centers in the CeF 3 crystals was very efficient as temperature increased. The 340 nm emission band may originate from some defects near Ce 3+, rather than Ce 3+ perturbed defects.
X-RAY ABSORPTION NEAR EDGE STRUCTURE INVESTIGATIONS OF GROUP III NITRIDES AND NITRIDED AIII-BV SEMICONDUCTOR SURFACES — FEFF CALCULATIONS AND ELECTRON YIELD MEASUREMENTS
Authors: CHASSÉ T. , HALLMEIER K. H. , HECHT J.-D. , FROST F.
Published: October 2002

Multiple scattering calculations using the FEFF-8 code were applied to simulate the X-ray absorption spectra recorded at the nitrogen K edge of III-N compounds. The major features of experimental N K XANES, including polarization effects, are well reproduced by the calculations, as is demonstrated for GaN. Further, FEFF calculations have been performed to investigate N bombardment-induced defects in III-V semiconductor surface layers. Recently reported nitrogen ion bombardment-induced spectral features of the N K absorption edge may be related to implanted nitrogen molecules by comparing experimental and calculated N K XANES.
SURFACE AND INTERFACE INVESTIGATION OF NANOMETRIC DIELECTRIC FILMS ON Si AND ON SiC
Authors: DA ROSA E. B. O. , KRUG C. , RADTKE C. , PEZZI R. P. , MIOTTI L. , BRANDÃO R. , MORAIS J. , BAUMVOL I. J. R. , STEDILE F. C.
Published: October 2002

Dielectric films on Si or SiC were investigated using angle-resolved X-ray photoelectron spectroscopy (ARXPS) and ion beam analysis techniques, namely high and low energy ion scattering (RBS and LEIS) and narrow nuclear resonance profiling (NRP) combined with isotopic substitution. For the Si substrate, attention was focused on the thermal stability of materials candidate to replacing SiO 2 in Si-based microelectronic devices (so-called "high-k dielectrics"): Al 2 O 3, ZrSi x O y, ZrAl x O y, HfSi x O y, and GdSi x O y. Mobility of different atomic species — especially Si and O — was observed at both the surface of the films and the interface with Si. Such atomic transport may have serious consequences concerning application of these materials in the microelectronics industry. For the SiC substrate, attention was focused on the initial stages of thermal oxidation in O 2, seeking an understanding of its poorer electrical quality as compared to SiO 2– Si . It was found that the initial oxidation products are silicon oxycarbides ( SiC x O y), while for longer oxidation times a mixture of SiC x O y and SiO2 is formed in the near surface region of the growing film. The composition of the near surface region of such thin films is very similar to that reported in previous investigations for the near interface region when thicker oxides films are grown on SiC.
BURST REACTION OF THIN FILMS EXCITED BY HIGH-FLUX SOFT X-RAYS
Authors: KANASHIMA TAKESHI , OKUYAMA MASANORI , OKAMOTO HIROAKI , HATTORI KIMINORI , OHASHI HARUHIKO , ISHIGURO EIJI
Published: October 2002

High-flux soft-X-ray irradiation effects were investigated for the thick a-Si:H and μc-Si:H films, glass, MgF 2 and CaF 2 plates. The a-Si:H film of 7500 nm thickness has been burst, and its broken fragments flew off within several seconds. From the changes of Raman spectra before and after the irradiation and the film thickness dependence, it is thought that this is caused by rapid crystallization. SR-induced etching of glass, MgF 2 and CaF 2 plates has been observed. Photon energy dependence of the etching depth has been found. Exciting the Si K-shell is effective for etching the glass substrate. On the other hand, photon flux is important in the case of fluoride, and the maximum etching rate of CaF 2 is more than 1 μm/min.
INTRAMOLECULAR ENERGY BAND DISPERSION IN ORIENTED THIN FILM OF n-CF3(CF2)22CF3 STUDIED BY ANGLE-RESOLVED UPS AND THEORETICAL SIMULATION
Authors: YOSHIMURA DAISUKE , SEKI KAZUHIKO , MIYAMAE TAKAYUKI , ISHII HISAO , HASEGAWA SHINJI , OKUDAIRA KOJI KAMIYA , UENO NOBUO
Published: October 2002

Electronic structure of perfluorotetracosane [n- CF 3 ( CF 2)22 CF 3; PFT], which is an oligomer of poly(tetrafluoroethylene) (PTFE), was investigated by angle-resolved photoemission spectroscopy (ARUPS) with synchrotron radiation. Theoretical simulations of ARUPS spectra were also performed by the independent atomic center (IAC) approximation combined with ab initio molecular orbital (MO) calculations. Measured normal-emission spectra for end-on oriented (the long-chain axis of PFT is perpendicular to the surface) films showed an incident photon energy dependence due to the intramolecular energy band dispersion. The energy band structure along the long-chain direction of PFT obtained from measured and calculated spectra is also discussed.
EFFECTS OF AIR EXPOSURE AND Cs DEPOSITION ON THE ELECTRONIC STRUCTURE OF MULTIWALLED CARBON NANOTUBES
Authors: SUZUKI SATORU , WATANABE Y. , KIYOKURA T. , NATH K. G. , OGINO T. , HEUN S. , ZHU W. , BOWER C. , ZHOU O.
Published: October 2002

Electronic structural changes in multiwalled carbon nanotubes caused by adsorbates and Cs deposition were studied by photoemission spectroscopy. The adsorbates formed by air exposure slightly increased the work function. The increased work function is considered to be due to the surface dipole moment induced by the negatively charged adsorbates. On the other hand, the Cs deposition followed by the intercalation drastically decreased the work function. The results suggest that field emission current enhancement induced by adsorbates and by Cs deposition are based on essentially different mechanisms; that is, the former is associated with the formation of localized electronic states and the latter is mainly due to the work function decrease.
POLARIZATION PROPERTIES OF SYNCHROTRON RADIATION IN THE STUDY OF ANISOTROPIC INSULATING CRYSTALS
Authors: KOLOBANOV V. N. , KAMENSKIKH I. A. , MIKHAILIN V. V. , SHPINKOV I. N. , SPASSKY D. A. , VASIL'EV A. N. , ZADNEPROVSKY B. I. , POTKIN L. I. , ZIMMERER G.
Published: October 2002

The optical properties of a wide series of the tungstates with the scheelite and wolframite crystal structure at the threshold of the fundamental absorption region were studied. New information about the influence of the electronic states forming the bottom of the conduction band and the top of the valence band on the formation of emission centers and mechanisms of energy transfer to these centers was obtained.
OPTICAL PROPERTIES OF GLASSY CARBON
Authors: PAJASOVÁ L. , SOUKUP L. , JASTRABÍK L. , CHVOSTOVÁ D.
Published: October 2002

The optical constants and dielectric functions of a series of samples of glassy carbon subjected to a heat treatment from 1000°C to 3000°C have been evaluated in the spectral region of 1.5–13.8 eV. In the region of 1.5–5.0 eV the method of spectroscopic ellipsometry and multiangle reflectivity with p-polarized light was applied, while in the VUV region the optical constants were evaluated by means of multiangle reflectivity with partially polarized light as well as by means of Kramers–Kronig analysis.

The optical spectra are discussed, in analogy with graphite, in terms of single-electron transitions and π electron plasma excitations. The changes in the spectra by heating are ascribed to increasing average size of ordered regions and sample densification in the absence of three-dimensional graphitization.
OPTICAL COMPONENTS FOR POLARIZATION ANALYSIS AT THE VANADIUM L3 EDGE AND THE CARBON K EDGE
Authors: GRIMMER H. , ZAHARKO O. , HORISBERGER M. , MERTINS H.-CH. , SCHÄFERS F.
Published: October 2002

A complete polarization analysis of soft X-ray radiation with primary standards can be performed using a phase shifter in transmission and an analyzer in reflection. V/Ni multilayers produced at PSI by sputter deposition showed a phase shift |△| = 7.6° at 512 eV and a reflectance ratio Rs/Rp > 1000 for E in the range 507–512 eV. For Cr/C multilayers a phase shift |△| = 21° was found at 277 eV and Rs = 20%, Rs/Rp = 1400 at 278 eV. The values show that these components are suitable for polarization analysis at the mentioned energies.
ELECTRON OPTICS WITH CYLINDRICAL DEFLECTOR FOR SPIN-RESOLVED INVERSE PHOTOEMISSION SPECTROSCOPY
Authors: QIAO S. , KIMURA A. , MORIHARA A. , HASUI S. , KOTANI E. , TAKAYAMA H. , SHIMADA K. , NAMATAME H. , TANIGUCHI M.
Published: October 2002

For a spin-resolved inverse photoemission spectrometer, the most important component is the electron optics system consisting of a 90° deflector and lenses to transfer the spin-polarized electrons from a GaAs photocathode to the sample at high transmission. We adopt a cylindrical deflector when we construct a spin-resolved inverse photoemission spectrometer. A performance test shows that our electronic optics system has achieved 83% transmission, and also that the cylindrical deflector has no shortcoming compared to the spherical type.
HIGH SPATIAL RESOLUTION SOFT X-RAY PHOTOEMISSION STUDY OF WO3 THIN FILMS
Authors: LOZZI L. , PASSACANTANDO M. , SANTUCCI S. , LA ROSA S. , SVETCHNIKOV N. YU.
Published: October 2002

WO 3 thin film surface chemical composition has been studied by means of high resolution soft X-ray photoemission spectroscopy. Valence band and W 4f core levels have been analyzed on different sample positions and high lateral resolution images have been acquired. The valence band spectra have shown for the first time a marked increase of the W 5d density of state at the Fermi level, indicating the presence of metallic tungsten on the surface. This has been confirmed by the W 4f signal, which presents both metallic and oxidized phases. For the first time, spectromicroscopy on core states has clearly evidenced the presence of nonstoichiometric areas and a spatial localization of W 4+ states on the surface.
THE APPLICATION OF SCANNING PHOTOELECTRON MICROSCOPY OF THE PLS (POHANG LIGHT SOURCE) TO INVESTIGATION OF SEMICONDUCTOR DEVICES
Authors: LEE M. K. , SHIN H. J. , KIM G. B. , HONG C. K. , KIM O. H. , CHANG C. H.
Published: October 2002

Scanning photoelectron microscopy (SPEM) was used to investigate a semiconductor sensor chip and Cu patterns embedded in Si substrate. It was found that the line shift in X-ray photoelectron spectroscopy (XPS) caused by local charges on the passivated surface is proportional to the distance between the surface and the conducting layer of the sensor chip. By using the line shift in XPS, inner-layered microstructure of the sensor chip could be imaged without destroying the sample. The result for the Cu patterns indicates that the surface of Cu patterns is more contaminated with carbon in the air than the surface of the Si pattern.
IMAGING OF DICHROISM IN PHOTOEMISSION ELECTRON MICROSCOPY AT NONMAGNETIC MATERIALS USING CIRCULARLY POLARIZED SOFT X-RAYS
Authors: OELSNER A. , ZIETHEN CH. , FECHER G. H. , SCHÖNHENSE G.
Published: October 2002

A new approach for investigations of circular dichroism in the angular distribution of photoelectrons (CDAD) is presented. The image contrast using a photoemission line of a certain material is combined with imaging of the angular distribution pattern using a photoemission electron microscope (PEEM). CDAD can be used to investigate pure scattering information by means of the same instrument in microscopically selected regions on a surface. The experiment combines angle-resolved XPS imaging with the indirect mapping of the local environment of atoms by means of CDAD holography. In a conventional photoelectron diffraction or photoelectron holography experiment, it is necessary to move the sample and/or the detector; for example, a rotatable electron analyzer is used to map a full angular pattern. In the present approach, the diffraction plane is mapped for a certain kinetic energy of electrons in the backfocal plane. An imaging high-pass energy filter has been used in combination with the PEEM in order to acquire surface images and/or diffraction pattern maps. Direct photoemission from the W-4f core levels was observed at different photon polarization to obtain two images and two diffraction patterns of the W-4f emission line using light of opposite helicity. The agreement of calculations with the experimental result is satisfactory. This constitutes a very encouraging starting point for the use of the CDAD holography together with the PEEM technique providing mesoscopic and atomic as well as chemical resolution in microselected areas on solid surfaces.
DESIGN OF A FLAT FIELD SPECTROMETER FOR SOFT X-RAY EMISSION SPECTROSCOPY
Authors: TOKUSHIMA T. , HARADA Y. , WATANABE M. , TAKATA Y. , ISHIGURO E. , HIRAYA A. , SHIN S.
Published: October 2002

A spectrometer for soft X-ray emission spectroscopy was designed and constructed. The aims of this spectrometer are high detection efficiency and realizing the energy resolution of 1000 (E/ΔE) in a compact size. To satisfy these requirements, a flat field spectrometer with a varied line spacing grating and a CCD detector was chosen. Furthermore, the configuration without the entrance slit was employed. For compact flat field spectrometers, the spectral dispersion on the detector is sometimes smaller than the spatial resolution of existing detectors restricting maximum energy resolution. The spectral dispersion on the detector was optimized to balance with the spatial resolution of CCD. Optical performance was tested with a ray-tracing program. The spectrometer covers 250–900 eV, with two gratings. Taking into account the spatial resolution of a CCD detector, the maximum energy resolution of the spectrometer is estimated to be about 1000 (E/ΔE) for the beam size of 10 μm. Using the constructed spectrometer, test experiments were performed at the beamline BL27SU in SPring-8.
MICROSCOPIC ULTRAVIOLET PHOTOELECTRON SPECTROSCOPY USING He-I AND He-II RESONANCE LINES
Authors: KONDO YUZI , EJIMA TAKEO , TAKATSUKA HIROFUMI , WATANABE MAKOTO
Published: October 2002

A microscopic ultraviolet photoelectron spectrometer (micro-UPS) is developed using a Schwarzschild objective coated with the two-color multilayer which reflects efficiently both He-I (21.2 eV) and He-II (40.8 eV) resonance lines. The spot size by the use of a pinhole of 300 μm diameter is 5 μm, which was measured using the visible light from a Xe lamp. In the present micro-UPS, a pinhole of 2 mm diameter is used to gain sufficient photon intensity, so that the spot size is 25 μm. The valence band spectra of a NiWO 4 microcrystal, which cannot be grown in sufficient size, were measured by the present micro-UPS. The origin of atomic orbitals constituting the valence band of NiWO 4 was elucidated.
HIGH-RESOLUTION, LOW-TEMPERATURE PHOTOEMISSION SPECTROSCOPY AT THE HISOR LINEAR UNDULATOR BEAMLINE
Authors: SHIMADA KENYA , ARITA MASASHI , TAKEDA YUKIHARU , FUJINO HIROYUKI , KOBAYASHI KENICHI , NARIMURA TAKAMASA , NAMATAME HIROFUMI , TANIGUCHI MASAKI
Published: October 2002

In order to study the electronic states of solids, using high-resolution, low-temperature photoemission spectroscopy (PES) with tunable photon energies, we have constructed a high-resolution undulator beamline operating in the photon-energy range 26–300 eV at the compact 700 MeV electron-storage ring HiSOR located at Hiroshima University. By way of gas-phase experiments, with photon flux larger than 2 × 1010 photons/s, photon-energy resolving powers of E/ΔE > 16000 and 3800 were obtained at hν ~ 48 eV and ~ 244 eV, respectively. High-resolution PES experiments on evaporated Au at 8 K were performed at the beamline with a total energy resolution of ΔE = 12 meV at hν = 48 eV. Among the first experiments from the beamline, a resonant photoemission study of UNiSn is presented. The U 5f derived peak is significantly enhanced at hν = 98 eV.
MULTILAYER POLARIZERS FOR THE USE OF He-I AND He-II RESONANCE LINES
Authors: HATANO TADASHI , KONDO YUZI , SAITO KATSUHIKO , EJIMA TAKEO , WATANABE MAKOTO , TAKAHASHI MASAHIKO
Published: October 2002

Multilayer polarizers for the use of He resonance lines have been developed. Si/Mg and SiC/Mg multilayers were designed and fabricated for the He-I and He-II resonance lines, respectively. The performance was checked by the use of synchrotron radiation. The polarizance and s-reflectance of the He-II polarizer measured at an angle of incidence of 40° were 0.98 and 41%, respectively. The polarizance of the He-I polarizer measured at an angle of incidence of 31.5° was 0.96.
THE TRANSITION FROM AMORPHOUS SILICON OXIDE TO CRYSTALLINE SILICON STUDIED BY PHOTOELECTRON DIFFRACTION
Authors: WESTPHAL C. , DREINER S. , SCHÜRMANN M. , ZACHARIAS H.
Published: October 2002

Angle-scanned photoelectron diffraction patterns of the Si 2p signal of oxidized Si(111) and Si(001) surfaces have been recorded and compared with simulations. The chemically shifted components of the Si 2p signal were deconvoluted by least squares fitting. The different oxidation states exhibit individual diffraction patterns for both surface orientations, indicating a different environment for each suboxide. For the Si(111) surface the results agree with a previously proposed sharp interface, whereas a graded interface is indicated for the Si(001) surface.
STUDY OF COMPACT X-RAY LASER PUMPED BY A PULSE-TRAIN LASER
Authors: YAMAGUCHI NAOHIRO , FUJIKAWA CHIEMI , HARA TAMIO
Published: October 2002

An advanced experiment has been performed to improve X-ray laser output in the recombination plasma scheme. Two 11-mm-long plasmas were produced by laser irradiation so that each axis aligned into a line consisting the double-target configuration. X-ray intensity of the 15.47 nm transition line of the Li-like Al ion was enhanced in the double-target scheme. A half-cavity experiment in the double-target configuration was also performed, and the enhancement of X-ray was also observed. The results in the half-cavity experiment were consistent with an estimation, where the two plasmas having positive gain contribute to amplify X-rays passing through plasmas and reflecting from the multilayer mirror. Measurements have been started to clarify spatial coherence of the lasing X-ray beam by using the dispersing coherent diagnostic system.
A POWERFUL SOURCE OF BROADBAND VUV RADIATION BASED ON A MULTICHANNEL SLIDING DISCHARGE
Authors: TCHEREMISKINE V. I. , SENTIS M. L. , SABONNADIERE M. P. , MIKHEEV L. D.
Published: October 2002

A powerful source of broadband UV-VUV radiation is developed on the base of a multichannel sliding discharge. The discharge having a radiating surface of hundreds of cm 2 is initiated simultaneously along several dozens of parallel linear channels located close to each other. The design of the discharge electric circuit allows a remarkably fast energy deposition into plasma: up to 4 kJ during 1.5 μs. Absolute measurements of discharge VUV radiation are performed by the method of spectrally selective dynamic actinometry. The total photon flux produced by the source within the spectral range of 120–200 nm reaches 1026 photons/s.
EXPERIMENTAL PHOTOHOLE LIFETIMES DERIVED FROM TWO-DIMENSIONAL STATES IN Ag(111) FILMS DEPOSITED ONTO H-PASSIVATED Si(111)-(1 × 1) SURFACES
Authors: ARRANZ A. , SÁNCHEZ-ROYO J. F. , AVILA J. , PÉREZ-DIESTE V. , ASENSIO M. C.
Published: October 2002

The linewidth of two-dimensional states appearing in the valence band spectra of 6–12-monolayer Ag(111) films deposited onto H-passivated Si (111)-(1 × 1) substrates has been analyzed in order to obtain a lower limit of the photohole lifetime. An inverse quadratic energy dependence is expected according to the Fermi liquid theory. However, in contrast with the observed in the literature for Ag single crystals, an inverse linear energy dependence has been found for the photohole lifetime. This discrepancy could be attributed to the quantization in the Γ-L direction of the Ag-sp states available for the hole decay, which does not fulfill the energy-independent density of states hypothesis of the Fermi liquid theory.
SPIN-RESOLVED PHOTOELECTRON SPECTROSCOPY OF ULTRATHIN Fe FILMS ON GaAs(001)
Authors: TAKAHASHI N. , ZHANG T. , SPANGENBERG M. , GREIG D. , SHEN T.-H. , CORNELIUS S. , SEDDON E. A. , MATTHEW J. A. D.
Published: October 2002

Thin epitaxial Fe films were grown on singular and vicinal GaAs(001) substrates, and their magnetic and electronic structures were investigated by synchrotron-based spin-resolved and spin-integrated photoelectron spectroscopy with different Fe thickness. There were two types of substrates: one was a Si-doped n-type GaAs(001) surface with doping concentration of 2 × 1018 cm -3 (singular substrate), and the other was orientated by 3° toward the (111)A direction (vicinal substrate). Spin polarization of the secondary electron peak at different growth stages of Fe coverage for the singular substrate sample and the vicinal one were measured. In the case of singular substrates, there was a dependence of their initial surface reconstruction, which is associated with complex domain structure, while no such the dependence was observed in the case of vicinal substrates. The result from the vicinal sample suggests the geometrical influence of the initial surface stoichiometry of the substrate.
ELECTRONIC STRUCTURE OF Ag THIN FILMS ON A Ge(001) SURFACE
Authors: NAKATSUJI K. , YAMADA M. , OHNO S. , NAITOH Y. , IIMORI T. , OKUDA T. , HARASAWA A. , KINOSHITA T. , KOMORI F.
Published: October 2002

We have studied the electronic structure of Ag thin films of monoatomic height grown on a Ge(001) surface at 95 K by using photoelectron spectroscopy. All the surface states on the clean Ge surface vanished and Ag 5s derived state appeared in the bulk band gap just below the Fermi level. These suggest a strong interaction with the substrate. On the other hand, on three-dimensional (3D) islands formed on a room temperature substrate, small changes were found in Ge 3d spectrum from the clean surface. Each of the Ag 3D islands already had bulklike feature in the valence band structure. The results are consistent with recent observation by scanning tunneling microscopy.
IN-SITU CORE-LEVEL PHOTOELECTRON SPECTROSCOPY OF ADSORBATES ON SURFACES INVOLVING A MOLECULAR BEAM — GENERAL SETUP AND FIRST EXPERIMENTS
Authors: DENECKE R. , KINNE M. , WHELAN C. M. , STEINRÜCK H.-P.
Published: October 2002

In this contribution we introduce a new apparatus combining high-resolution photoelectron spectroscopy and supersonic molecular beam techniques designed to follow simple surface reactions like adsorption, desorption or oxidation in situ in a time- and temperature-resolved manner. Using high brightness synchrotron radiation high resolution core-level spectra can be obtained in less than 3 s. The molecular beam allows for local pressures of up to 1 · 10-5 mbar and translational energies of the molecules of up to 2 eV in the case of CO. Preliminary examples of CO adsorption on Pt(111) are shown, where kinetic parameters can be derived from the coverage dependence of the different adsorption sites.
SYNCHROTRON RADIATION PHOTOEMISSION AND INFRARED SPECTROSCOPY STUDY OF ADSORPTION AND DECOMPOSITION OF DICHLOROSILANE ON Si(100)(2 × 1)
Authors: KAMAKURA NOZOMU , SHINOHARA MASANORI , WATANABE HAYATO , KUWANO TAKAYUKI , SEYAMA AKIO , KIMURA YASUO , NIWANO MICHIO
Published: October 2002

We have used synchrotron radiation photoemission (SR-PES) and infrared absorption spectroscopy (IRAS) to investigate in situ the adsorption and decomposition of SiH 2 Cl 2 on Si (100)(2 × 1). Si 2p core level photoemission spectra and IRAS spectra in the Si–H stretching vibration region of the surface exposed to SiH 2 Cl 2 at room temperature have been measured to elucidate how SiH 2 Cl 2 adsorbs on the surface. PES data show that monochloride (SiCl) and hydride species ( SiH x) are generated upon dichlorosilane adsorption. IRAS data demonstrate that at initial stages of SiH 2 Cl 2 adsorption, the monohydride, the dihydride ( SiH 2) and the Cl-substituted hydride (–SiHCl) are populated on the surface. Comparison of PES and IRAS data indicates that Si–Cl bonds of the SiH 2 Cl 2 molecule are readily ruptured upon adsorption of dichlorosilane on the Si (100)(2 × 1).
REINVESTIGATION OF THE ELECTRONIC STRUCTURE AND FERROMAGNETISM OF THE NONRECONSTRUCTED Cr(001) 1 × 1 SURFACE
Authors: NAKAJIMA H. , PUKIRD S. , SURABAN W. , SAITOH T. , KAKIZAKI A.
Published: October 2002

In angle- and spin-resolved photoemission experiments, we have observed that the ferromagnetic order of the Cr(001) surface is strongly influenced by oxygen concentration. Oxygen atoms of a few atomic percent of the total volume have a substantial influence on the ferromagnetic order of the Cr(001) surface.
CoL EMISSION SPECTRA OF LaCoO3 AT LOW TEMPERATURE
Authors: TAGUCHI Y. , OKABAYASHI Y. , UOZUMI T. , MIMURA K. , ICHIKAWA K. , KAWAMATA S. , OKUDA K. , AITA O.
Published: October 2002

Co 3d → 2p X-ray emission spectra of LaCoO 3 in the Co 2p photoabsorption region are measured at 40 and 300 K. The spectra mainly reveal features nearly independent of excitation photon energy. This indicates the highly covalent or strongly hybridized nature of the Co 3d state. The emission component showing resonant behavior is also observed. The temperature dependence of the resonant emission confirms that the wave function of Co 3d electrons is totally symmetric in the low-spin ground state and that for the spin state excited thermally through the magnetic transition around 100 K is not.
MAGNETIC MICROSPECTROSCOPY BY A COMBINATION OF XMCD AND PEEM
Authors: IMADA S. , SUGA S. , KUCH W. , KIRSCHNER J.
Published: October 2002

The benefits of combining soft X-ray magnetic circular dichroism and photoelectron microscopy are demonstrated by applying this combination (XMCD–PEEM) not only to magnetic domain imaging but also to quantitative evaluation of the distribution of spin and orbital magnetic moments. The latter takes full advantage of the spectroscopic aspect of XMCD–PEEM.
DICHROISM IN ANGLE-RESOLVED PHOTOEMISSION FROM Pt(111)
Authors: FECHER G. H. , BRAUN J. , OELSNER A. , OSTERTAG CH. , SCHÖNHENSE G.
Published: October 2002

The angular dependence of the circular dichroism in photoemission from Pt(111) was investigated for excitation with VUV and soft X-ray radiation. VUV excitation was used to probe band structure and the circular dichroism for valence band emission. The measurements are compared to full relativistic single step photoemission calculations. XPS was used to investigate the circular dichroism in emission from the 4f core level. In this case, the dichroism is induced by photoelectron diffraction. First results from single step core level calculations are compared to the experimental observations.
DIRECT EVIDENCE FOR ITINERANT MAGNETITE ABOVE AND BELOW THE VERWEY TRANSITION TEMPERATURE
Authors: CAI Y. Q. , NAKATSUJI K. , OHNO S. , IIMORI T. , YAMADA M. , KOMORI F.
Published: October 2002

The valence electronic states of Fe 3 O 4(111) films on Pt(111) were studied using temperature-dependent spin- and angle-resolved photoemission spectroscopy with synchrotron radiation. The majority- and minority-spin partial density of states (DOS) has been obtained at 300 K and 100 K, above and below the Verwey transition temperature (TV ~ 120 K ). The spectra still show substantial k-dependence at 100 K in the 3d region. This provides the most direct experimental evidence that the 3d electrons are itinerant even at T < TV.
ANGLE-RESOLVED PHOTOEMISSION SPECTROSCOPY AND MAGNETIC CIRCULAR DICHROISM IN Fe-INTERCALATED TiS2
Authors: YAMASAKI A. , IMADA S. , SEKIYAMA A. , SUGA S. , MATSUSHITA T. , MURO T. , SAITOH Y. , NEGISHI H. , SASAKI M.
Published: October 2002

In order to directly investigate the energy band dispersion and the origin of the magnetic moment in intercalation compounds Fe x TiS 2, we have measured the angle-resolved photoemission (ARPES) spectrum and the magnetic circular dichroism (MCD) of the soft X-ray core absorption (XAS) spectra using a synchrotron light source. The energy band dispersion is clearly observed in the Ti 2p3/2 (eg) on-resonance ARPES spectra. In the Ti 2p XAS spectra the MCD is clearly seen, suggesting that a magnetic moment is induced on the Ti atom through the hybridization with the Fe 3d orbitals. We quantitatively estimate the orbital and spin magnetic moments of the Fe and Ti atoms by using the magneto-optical sum rules.
PROBING THE Mn3+ SUBLATTICE IN La0.5Ca0.5MnO3 BY RESONANT INELASTIC SOFT X-RAY SCATTERING AT THE MnL2,3 EDGE
Authors: BUTORIN S. M. , SÅTHE C. , SAALEM F. , NORDGREN J. , ZHU X.-M.
Published: October 2002

Resonant soft X-ray scattering spectra of a La 0.5 Ca 0.5 MnO 3 thin film were measured at varying energies of the incident photon beam across Mn 2p thresholds. The data are analyzed within the framework of the Anderson impurity model and full multiplet theory. The scattering profiles of the film are reasonably well reproduced by model calculations for the Mn 3+ system, in contrast to the absorption spectrum at the Mn L2,3 edge for which the contribution of the Mn 4+ sublattice is required to be taken into account. The obtained agreement between calculations and experiment indicates that in this case resonant inelastic scattering mainly probes the local electronic structure at the Mn 3+ sites in the La 0.5 Ca 0.5 MnO 3 film. In turn, Mn 4+ sites mainly contribute to ordinary Lα,β X-ray emission due to relaxations in the intermediate state of the spectroscopic process. Such a situation can occur when the system favors a phase separation rather than checkerboard charge ordering of Mn 3+ and Mn 4+ sites.
MAGNETIC COUPLING IN Co/Cu MULTILAYERS: FIELD-DEPENDENT ANTIFERROMAGNETIC ORDERING INVESTIGATED BY RESONANT X-RAY SCATTERING
Authors: SPEZZANI CARLO , TORELLI PIERO , SACCHI MAURIZIO , DELAUNAY RENAUD , HAGUE CORYN F. , MIRONE ALESSANDRO , SALMASSI FAHRAD , GULLIKSON ERIC M. , UNDERWOOD JAMES H.
Published: October 2002

By simultaneous measurements of sample resistance and of X-ray resonant scattering, we tried to establish a direct correlation between magnetoresistance (MR) and antiferromagnetic (AF) order in a Co/Cu metallic multilayer. Field-dependent scattered intensity has been measured in a geometrical configuration corresponding to the Bragg peak coming from the AF coupling, at a photon energy close to the Co L 3 absorption edge (hν = 776.5 eV ). The comparison between measurements of the scattered intensity and of the resistance clearly shows a direct correlation between AF order and MR.
TWO-BAND MAGNETO-OPTICAL ELEMENTS FOR SOFT X-RAY POLARIZATION ANALYSIS AT THE Fe, Co 2p AND Gd 3d EDGES
Authors: MELTCHAKOV E. , JARK W. , DI FONZO S. , MERTINS H.-CH. , SCHEER M. , SCHÄFERS F.
Published: October 2002

We present angle-, energy- and polarization-dependent magneto-optical properties of Gd/Fe and Gd/Co multilayers with periods of the order of 1 nm for the photon energy range of 700–1230 eV. In the vicinity of the 2p absorption edge of transition metals (TM) and the 3d edge of the rare earth elements (RE), the X ray magnetic circular dichroism (XMCD) was measured in transmission and the X ray resonant magnetic scattering (XRMS) was investigated in L-MOKE geometry. The magnetic state of Gd could be realized at room temperature. Based on these data a calibrated detector of the polarization state of synchrotron radiation has been developed.
QUADRUPOLAR CHARACTER OF THE Ti K-EDGE PREPEAKS IN TiO2 BY RESONANT AUGER
Authors: DANGER J. , LE FEVRE P. , MAGNAN H. , CHANDESRIS D. , BOURGEOIS S. , JUPILLE J. , EICKHOFF T. , DRUBE W.
Published: October 2002

Resonant spectroscopies offer a new opportunity to get more insight into excited electronic states by studying line shapes and intensities of decay processes. For photon excitations in the pre-K-edge region, the Ti KL 2,3 L 2,3 Auger spectra in TiO 2 show additional peaks when an electron is promoted in localized d-like states via a quadrupolar transition. This resonant process is used to unravel the respective contributions of quadrupolar and dipolar transitions to the absorption edge prepeaks.
MULTISITE EFFECTS ON THE CORE-LEVEL PHOTOEMISSION IN Sr2RuO4
Authors: OKADA KOZO
Published: October 2002

Multi-Ru-site effects on the photoemission from the Ru 3d core level in Sr 2 RuO 4 are discussed on the basis of numerical diagonalization calculations for large-size cluster models. It is shown that the electrons on the Ru 4d ions neighboring the core-hole site participate actively in the core-hole screening, which indicates the importance of so-called "nonlocal screening" in Sr 2 RuO 4. However, since it occurs via the Ru 4d(xy)– O 2pπ bonding, the photoemission intensity which corresponds to the nonlocal screening is not large, compared with the Cu 2p photoemission in high-Tc-related cuprates. From the spectral analysis, the Coulomb interaction strength between Ru 4d electrons is estimated to be comparable with the width of Ru dε bands. In other words, Sr 2 RuO 4 belongs to a category of strongly correlated electron systems.
HIGH-RESOLUTION ANGLE-RESOLVED PHOTOEMISSION STUDY OF η-MO4O11
Authors: FUJISAWA H. , KUMIGASHIRA H. , TAKAHASHI T. , KURITA R. , KOYANO M.
Published: October 2002

We have performed high-resolution angle-resolved photoemission spectroscopy (ARPES) on a quasi two-dimensional (2D) conductor η- Mo 4 O 11. The band dispersions near E F and the Fermi-surface topology determined by ARPES show a qualitatively good agreement with the band-structure calculation, although the observed width of Mo 4d bands forming the Fermi surface is two-to-three times larger in the calculation. We have clearly identified two nesting vectors in the ARPES-derived Fermi surface, which show a good agreement with the CDW wave vectors obtained from X-ray diffraction experiments. The present ARPES results indicate that the CDW instability in η- Mo 4 O 11 is driven by "the hidden 1D Fermi-surface nesting" due to the quasi 1D chains in the crystal.