bluuebunny/crossref_metadata_2025 huggingface dataset:
The Expressive Function of Constitutional Amendment Rules
Authors: Albert Richard
Published: March 2014

The current scholarly focus on informal constitutional amendment has obscured the continuing relevance of formal amendment rules. In this article, I return our attention to formal amendment in order to show that formal amendment rules—not formal amendments but formal amendment rules themselves—perform an underappreciated function: to express constitutional values. Drawing from national constitutions, in particular the Canadian, South African, German, and United States constitutions, I illustrate how constitutional designers may deploy formal amendment rules to create a formal constitutional hierarchy that reflects special political commitments. That formal amendment rules may express constitutional values is both a clarifying and a complicating contribution to their study. This thesis clarifies the study of formal amendment rules by showing that such rules may serve a function that scholars have yet to attribute to them; yet it complicates this study by indicating that the constitutional text alone cannot prove whether the constitutional values expressed in formal amendment rules represent authentic or inauthentic political commitments.
Assimilation or Cultural Difference? Palestinian Immigrants in Honduras
Authors: Gutiérrez Rivera Lirio
Published: March 2014

This article looks at Palestinian immigrants in contemporary Honduras. It questions the general assumption that Palestinians have successfully assimilated into predominantly mestizo societies. It shows that the Palestinian community has maintained various features and references, such as their religious affiliation and their activity in commerce and trade, that make them a culturally differentiated group. This article also explores why, against the recent backdrop of multiculturalism, the Palestinian immigrant community have not mobilized an ethnic identity in order to gain access to resources or demand collective recognition. Furthermore, it shows that Palestinian immigrants have benefitted from various macro and local political and economic factors and policies that contributed to the accumulation of different forms of capital throughout the 20th century.
La contracción de las redes de contrabando de migrantes en México
Authors: Izcara Palacios Simón Pedro
Published: March 2014

Tanto o discurso oficial quanto o acadêmico sustentam que o contrabando de migrantes na fronteira entre o México e os Estados Unidos da América é uma atividade cada vez mais complexa e lucrativa, que requer a operação de redes extensas e nexos com o crime organizado. Os resultados desta pesquisa, baseada em uma metodologia qualitativa que inclui entrevistas em profundidade com 115 contrabandistas de migrantes, descrevem um cenário diferente. Os coiotes devem compartilhar seu lucro com novos atores; como consequência, algumas redes de contrabando de migrantes estão se vendo obrigadas a despedir alguns de seus membros para diminuir os custos de operação, enquanto outras redes decidiram não empregar mais pessoas para fazer com que esse negócio continue sendo rentável.
Uso de tecnologías de la información y la comunicación en familias caleñas con migrantes en España
Authors: Ramírez Martínez Juan Pablo
Published: March 2014

The article presents the main results of a study aimed at establishing the role of communication practices in sustaining family and emotional ties between migrants and their families. Family communication is studied in transnational households through semistructured interviews that identify the means by which migrants communicate with home, observing the uses, frequencies and possibilities these technical supports offer, as well as the importance of certain topics related to the content of the communication, identifying communicative aspects that establish an everyday reality and continuity in family and emotional relationships.
El rol de la prensa escrita en la reproducción de la violencia en el conflicto entre Chile y Perú. Propuestas de paz desde la comunicación
Authors: Arévalo Salinas Alex Iván
Published: March 2014

The following article describes the role of the written press of Chile and Peru in the development of some conflictive relations between these countries. The analysis indicates that there are three discursive strategies to legitimize mutual rejection, such as the negative representation of otherness, the exaltation of competition for economic success, and the promotion of national identity based on the values attributed to the military of the Pacific War. The conclusions propose two measures to transform these discourses: the development of social publicity campaigns and the creation of a code of ethics that establishes recommendations for appropriate journalistic treatment of the relations between these countries.
Experiencia migrante y apropiaciones espaciales: una etnografía visual en las inmediaciones del Terminal Internacional de Arica (Chile)
Authors: Lube-Guizardi Menara , Heredia Orlando , Muñoz Arlene , Riquelme Grecia , Valdebenito Felipe
Published: March 2014

This essay presents a visual ethnography about the movements, spatial appropriations, and the migrant urban experience surrounding the International Bus Terminal of Arica (North of Chile). The Terminal, as it is popularly known, is a trans-bordered scenario, constituting one of the urban loci that articulate the national frontiers crossing between Chile, Peru and Bolivia. Inside the Terminal, and in its vicinity, we can observe spatial appropriations carried on by migrants and autochthones, which are involved in the commercial activities between national borders or in the migrant labor market so important to Arica’s economic reality.
Effects of magnetic nanoparticle films on the electrical characteristics of dc superconducting quantum interference devices
Authors: Okumura Takayuki , Ito Hiroshi , Yano Shun , Taniguchi Soya , Akaike Hiroyuki , Fujimaki Akira
Published: March 2014

We evaluated the effects of Fe3O4 magnetic nanoparticle (NP) films on the electrical characteristics of superconducting quantum interference devices (SQUIDs) at 4.2 K to enhance the performance of superconducting circuits. The NP films were formed directly on the SQUIDs. For SQUIDs with 5-nm-NP films, the SQUID inductance increased almost linearly with the NP film thickness, reaching 19.7% at an NP film thickness of 990 nm. An increase in NP size from 5 to 20 nm reduced that in the SQUID inductance. On the other hand, no clear effects on the current–voltage characteristics of SQUIDs were observed for 5- and 10-nm-NP films, while the critical currents of some SQUIDs with 20-nm-NP films were reduced.
Structural Analysis of a Series of Oxygen-coordinated Al(III) in Aluminosilicate Minerals by X-Ray Absorption and NMR Spectrometries
Authors: Ichihashi H. , Kurisaki T. , Yamaguchi T. , Yokoyama T. , Wakita H.
Published: March 2014

Al K X-ray Absorption Near-Edge Structure (XANES) spectra of a series of aluminosilicate minerals were analyzed by DV-Xα MO method. Aluminosilicate minerals in nature contain various oxygen-coordinated Al(III), e.g. four-, five- and six- (1:1), and six-fold. In this study, the Al K XANES spectra of anorthite [CaAl2Si2O8], andalusite [Al2SiO5] and kaolinite [Al2Si2O5(OH)4] were measured and analyzed in terms of the electron transition probabilities. Their coordination structures and bond characters were discussed. The results were also compared with those of NMR measurements.
Ab Initio Structural Study on Nb-doped Pb(Zr0.97Ti0.03)O3 Ceramic Material by Synchrotron X-Ray Diffraction
Authors: Liu Hongchao , Toraya Hideo
Published: March 2014

X-ray powder diffraction pattern of Nb-doped Pb(Zr0.97Ti0.03)O3 ceramic material was collected with synchrotron radiation source. Its crystal structure was investigated by ab initio crystal structure analysis based on the powder diffraction data. The result showed that this material is in orthorhombic symmetry and unit-cell parameters are a=5.86295(4)Å, b=11.74014(7)Å and c=8.20686(4)Å. Both the full profile fitting and structural analysis supported that the most appropriate space group is Pnnm, rather than the widely accepted Pbam or Pba2. The structural data revealed Zr displacement along z-axis and local disorder in the oxygen substructure.
X-Ray Absorption Spectroscopy Studies of La1-xSrxFeO3
Authors: Chang C. L. , Chern G. , Tai M. F. , Su Y. W. , Dong C. L. , Liu S. Y. , Hwang C. S. , Tseng P. K.
Published: March 2014

We report the Fe K-edge and La L
2,3-edge x-ray absorption spectroscopy (XAS) studies of a series of La1-xSrxFeO3 samples. The chemical shift and the pre-edge feature strength of Fe K-edge spectra show that both the Fe valence and its 3d holes increase with Sr concentration up to x=0.8 then saturate. Systematic variations in the whiteline intensity and the above-edge feature in the La L
2,3-edge XAS spectra with Sr concentration indicate that the local structure and the electronic state of La are both affected by Sr doping. The correlation between the Fe valence change and the structural variation are briefly discussed.
EXAFS Study of Coordination Structures of Gd-doped Ba2In2O5
Authors: Uchimoto Yoshiharu , Kinuhata Masanori , Yao Takeshi
Published: March 2014

Crystal structures of undoped and Gd-doped Ba2In2O5 were analyzed by EXAFS and the powder X-ray Rietveld method. Rietveld analysis indicated that Ba2In2O5 is belonging to orthorhombic Ibm2 space group and that Ba2(In1-xGdx)2O5 (X=0.20 and 0.30) is belonging to cubic Pm3m space group at room temperature.
Foulier transform of In K-edge EXAFS of Ba2(In1-xGdx)2O5 (X=0.00, 0.20, 0.30) showed a peak between 1.2 and 2.0 Å attributed to the nearest oxide ions around In3+ cation. The peak was back-Fourier transformed, and the structural parameters were refined by the least square fitting. It was indicated that the coordination number of In3+ cation decreased with increasing Gd3+ cation content. This result indicates that coordination number of Gd3+ cation is not 4 but 6 preferably.
Resonant Inelastic X-Ray Scattering from Strongly Correlated Copper Oxides
Authors: Hill John P. , Kao Chi-Chang , Zimmermann Martin v. , Hämäläinen Keijo , Huotari Simo , Berman Lonny E. , Caliebe Wolfgang A. L. , Hirota Kazuma , Matsubara M. , Kotani Akio , Peng Jian Lang , Greene Richard L. , Tsukada Ichiro , Masuda Takatsugu , Uchinokura Kunimitsu
Published: March 2014

We report resonant inelastic x-ray scattering from Nd2CuO4 and two other copper oxides, YBa2Cu3O7-δ and CuGeO3. In each case an excitation of ∼ 6 eV is observed when the incident photon energy is tuned through the Cu K-edge. Calculations for Nd2CuO4, based on the Anderson impurity model identify this as a charge transfer excitation to the antibonding state. For Nd2CuO4, the incident energy dependence of the inelastic intensity exhibits a single resonance at 8990 eV, corresponding to a 1s3d
9
4p
π intermediate state. The absence of a resonance associated with the 1s3d
10
L4p
π intermediate state is attributed to non-local effects. Preliminary results from CuGeO3, which exhibit two resonances support this conclusion.
The MEM Charge Density Study of Rb2CsC60, K2RbC60, and Li2CsC60 by Synchrotron Radiation Powder Method
Authors: Takata Masaki , Machida Naoki , Nishibori Eiji , Umeda Buntaro , Sakata Makoto , Tamgaki Katsumi , Kosaka Mayumi , Hirosawa Ichiro , Mizuki Junichiro
Published: March 2014

A charge density study of alkali metal doped fullerenes, Rb2CsC60, K2RbC60 and Li2CsC60, was carried out at room temperature by the Maximum Entropy Method (MEM) combined with the Rietveld analysis using synchrotron powder data. The MEM charge densities of the C60 molecules show distinct differences related to the superconducting properties. For both K2RbC60 and Rb2CsC60, which are superconductors at low temperature, the C60 molecules were in a merohedral disorder. On the other hand, the C60 molecules in Li2CsC60; non-superconductor even at very low temperature, were in an orientational disorder. In the interatomic region between the C60 molecules and doped metal atoms, any significant overlapped charge densities related to covalent bond were not found for all three materials. This is the clear evidence for that superconductivity of these materials and covalency of doped metals have no correlation at all. Instead, the charge deficiencies of the doped metal atoms which should be associated with charge transfer from the metal atoms to the C60 molecule seems to have a strong correlation to the superconducting transition temperature, Tc, i.e. the higher the Tc, the more the deficiencies.
Study of the High Frequency Dynamics in Glass-Forming Systems
Authors: Masciovecchio Claudio , Monaco Giulio , Ruocco Giancarlo , Sette Francesco
Published: March 2014

The dynamic structure factors of three glass-formers, o-terphenyl, glycerol and vitreous silica, have been measured at different temperatures T and exchanged momenta Q using inelastic x-ray scattering. We find propagating excitations at wavelengths approaching the interparticle separation region. We will show that these excitations are strongly related to the excess of vibrational states in glasses. Moreover, taking as example the measurements performed on o-terphenyl, we demonstrate that the temperature dependence of the dispersion curves allows the determination of the infinite frequency sound velocity C
∞ (T). The derived values of C
∞ (T) in the liquid phase can be used to discriminate among different phenomenological models previously proposed.
Cation Structure in Binary Potassium Borate Glasses
Authors: Handa Katsumi , Iwadate Yasuhiko , Umesaki Norimasa
Published: March 2014

XAFS studies of network modifying cations in alkali borate glasses have made an important contribution to our understanding of the structure of glass. Using the synchrotron XAFS facility, we have performed to determine the local structure in K2O-B2O3 glasses in order to elucidate the environment of B-O network modifying K+ ions. The average coordination number N

B-O
of oxygen around K+ cations and the mean distance r

B-O
for K-O correlations are found to be approximately 6 and 2.83∼2.86Å, respectively. The XAFS results are in good agreement with our X-ray diffraction and MD simulation results.
A Reverse Monte Carlo Study of Lead Metasilicate Glass
Authors: Suzuya Kentaro , Kohara Shinji , Ohno Hideo
Published: March 2014

Total structure factors from anomalous X-ray scattering (AXS) and neutron diffraction (ND) measurements on lead metasilicate (PbSiO3) glass have been analyzed by the reverse Monte Carlo (RMC) modelling technique to generate a three-dimensional structural model of the glass. The structure determined indicates an ordered distribution of Pb in the glass, suggesting that the intermediate-range order (IRO) is due to the presence of a ring-like structure made up of irregular PbO4 pyramids. This network-former-like role of the Pb ions may provide a crucial key to the understanding of the glass-forming ability of the PbO-SiO2 system especially up to high concentrations of PbO.
XAFS Studies of Alkaline-Earth Borate Glasses
Authors: Handa Katsumi , Ohtori Norikazu , Iwadate Yasuhiko , Umesaki Norimasa , Iwasaki Hirosi
Published: March 2014

The local structure obtained from calcium K-edge XAFS experiments in CaO-B2O3 glasses is described. The average coordination number of oxygen around Ca2+ ions and the mean distance for Ca-O are found to be approximately 6 and 2.40∼2.41Å, respectively. The Ca2+ ions have a disordered octahedral geometry and a strong preference to reside in vicinity of negatively charged non-bridging and bridging oxygen in the large cages of the B-O network structure. The XAFS results are in good agreement with MD simulation results.
X-Ray Diffraction Analysis of Molten Trivalent Halides
Authors: Okamoto Yoshihiro , Hayashi Hirokazu , Ogawa Toru
Published: March 2014

Molten structures of some trivalent halides were investigated by high-temperature X-ray diffraction method. Shortranged structure of the melts, in which cation tends to be surrounded by six halide ions, was precisely determined from radial distribution function G(r). A first sharp diffraction peak corresponding to a medium-ranged structural order was detected in those melts. In the present work, correlation between the medium-ranged structural order and dynamic properties is discussed in view of the molecular dynamics simulation technique.
Structure of K2O–TeO2 Glasses
Authors: Akagi R. , Handa K. , Ohtori N. , Hannon A. C. , Tatsumisago M. , Umesaki N.
Published: March 2014

The structure at room temperature and structural change from room temperature to the temperature above melting point (T

m
) of K2O-TeO2 glasses were studied by the use of XAFS spectroscopy, high-temperature Raman spectroscopy, high-temperature XRD and X-ray RDF (Radial Distribution Function). XAFS spectroscopy has indicated that K2O-TeO2 glasses consist of both TeO4 trigonal bipyramid (tbp) units and TeO3 trigonal pyramid (tp) units , and high-temperature Raman results have indicated that TeO4
tbp units convert to TeO3
tp units with the increase of temperature and by the addition of K2O in the K2O-TeO2 glasses. The high-temperature XRD and X-ray RDF results were in good agreement with the results of the high-temperature Raman spectroscopy. Furthermore, the XAFS spectroscopy has shown that potassium ions have a similar local structure in all K2O-TeO2 glasses studied.
Local Structure of Rare-earth Ions in Alkali Silicate Glasses Studied by Extended X-Ray Absorption Fine Structure
Authors: Yamaguchi Hirotaka , Takebe Hiromichi
Published: March 2014

Local structure of neodymium and erbium ions in alkali silicate glasses has been investigated by extended X-ray absorption fine structure (EXAFS). The coordination number and interatomic distance for the nearest neighbor oxygen ions change with the modifier alkali metal species. It is shown that these structural parameters vary as a function of the field strength of the alkali metal ions. The alkali metal ions are found to locate at the second nearest site of the rare-earth ions. In an erbium-doped potassium silicate glass, the erbium-potassium distance is determined to be 3.78 Å, which agrees with the calculated value by a molecular dynamics simulation of Cormier et al. [J. Non-Cryst. Solids 152 (1993) 225].
SAXS Study of Gelation, Aging and Drying of Silica-Polypropyleneglycol Hybrid Materials
Authors: Dahmouche K. , Santilli C. V. , Chaker J. A. , Pulcinelli S. H. , Craievich A. F.
Published: March 2014

New silica-polypropyleneglycol ormosils (organically modified silicates) with covalent bonds between the organic (polymer) and inorganic (silica) phases have been prepared by the sol-gel process. Their structural evolution during sol formation, sol-gel transition, gel aging and drying has been studied in situ by small-angle X-ray scattering (SAXS). The experimental SAXS curves corresponding to sols and gels exhibit features expected from fractal objects. Clusters of size around 55 Å with an initial fractal dimension D = 2.4 are formed in the sol. They are constituted of small primary silica particles chemically crosslinked at the end of the polymer chains. A strong liquid-like spatial correlation between the silica particles develops during drying due to the shrinkage of the polymeric network induced by water and ethanol evaporation. The continuous increase in SAXS intensity during drying, while the interparticle distance remains constant, is a consequence of the progressive growth of the dry fraction of the total volume. After drying, the gel structure consists of a rather compact arrangement of silica particles embedded in the polypropyleneglycol matrix.
Fermiology by Compton Scattering
Authors: Shiotani Nobuhiro
Published: March 2014

Recent results on the electron momentum density of simple metals are reviewed to illustrate how Compton scattering is unique and indispensable as a tool to study Fermiology of various materials. Reconstruction of the two- and the three-dimensional momentum density and occupation number density is also reviewed with presenting examples of Li, Li-Mg alloys and Cr.
Small-Angle X-Ray Scattering Analysis of Membrane Protein Porin
Authors: Watanabe Yasushi , Sano Yoh , Inoko Yoji
Published: March 2014

The native (intact) and denatured (unfolded) states of a trimeric integral membrane protein Porin were characterized by synchrotron radiation small-angle X-ray scattering. Native trimeric Porin in the presence of SDS showed a scattering curve with two peaks at q=1.5 and 2.4 nm-1. The scattering curve of denatured monomeric Porin had a single peak at q=1.6 nm-1 and was similar to a typical scattering pattern for the water-soluble protein polypeptide in SDS. The radius of gyration value of denatured monomeric Porin in SDS was much the same as that of its native trimer (ca. 4 nm). The patterns of Kratky plots at the native and denatured state were different from each other. This finding will be useful for the kinetic study in synchrotron radiation small-angle X-ray scattering experiments to understand the folding and assembly mechanism of the integral membrane protein.
Structure and Core Electron Absorption Spectra of Polyester Films
Authors: Ouchi Isuke , Nakai Ikuo , Kamada Masao , Tanaka Shin-ichiro , Gejyo Tatsuo , Hagiwara Tsuneo
Published: March 2014

Soft x-ray absorption spectra of oriented films of polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) of several tenth micron in thickness were measured by a transmission method. A similar resolution and the same dependence on the beam incident angle as obtained by a total electron yield method were observed in the oxygen K-edge region, but not in the carbon K-edge. IR spectra of the thin oriented sample films utilized in these measurements indicated their aromatic rings to be parallel to the film plane as found in the thick PET and PEN films. This fact conformed to the spectral change near the oxygen K-edge and gave a further support of the peak assignments made previously. The spectral behavior near the carbon K-edge was interpreted by the saturation effect which was due to the presence of greater number of carbon atoms in a repeat unit than oxygen atoms, and partially by strayed light effects.
Synchrotron X-Ray Scattering Study of the Strain Evolution in Thin AlN/Sapphire(0001) Films
Authors: Kang Hyon Choi , Seo Sun Hee , Noh Do Young
Published: March 2014

High-resolution synchrotron x-ray scattering measurements were used to study the strain relaxation of AlN/Sapphire (0001) films grown by radio frequency magnetron sputtering. Films thinner than ∼ 100 Å were highly strained, and grown as two-dimensional epitaxial layers. The exact condition for the extended domain matching was deduced. With increasing film thickness, the lattice strain was relieved, while columnar seeds start to nucleate on parts of the film. The columnar grains on the epitaxial layer, however, impeded the strain relaxation of the epitaxial layer underneath, which resulted in a non-uniform strain distribution in the film. The highly asymmetric AlN(0002) reflection of thick AlN films illustrates that the strain distribution is non-uniform.
XANES Analysis of Optical Activation Process of Er in Si:Er2O3 Thin Film: Electronic and Structural Modifications around Er
Authors: Ishii Masashi , Komuro Shuji , Morikawa Takitaro , Aoyagi Yoshinobu , Ishikawa Tetsuya , Ueki Tatzuo
Published: March 2014

Peak height and second-derivative analyses of Er LIII-edge X-ray absorption near edge structure (XANES) are performed to investigate the optical activation process of Er in Si:Er2O3 thin film produced by the laser ablation method. The as-ablated sample has a high resonant absorption peak, and the second-derivative analysis of the peak gives a singlet in contrast to the doublet for Er2O3 powder. This is explained by the concentration of the density of states (DOS) due to a higher order symmetry such as an ErO6 octahedron in the as-ablated sample. After annealing, a quasi-doublet is observed in the second-derivative spectrum, suggesting the distortion of the octahedral structure. The increment of photoluminescence intensity after annealing is considered to be caused by this symmetrical degradation.
X-Ray Diffraction Study of Barium Titanate Thin Films
Authors: Sakaue Kiyoshi , Takakura Yoshiyuki , Terauchi Hikaru , Awaji Naoki , Komiya Satoshi
Published: March 2014

Sychrotron diffraction study of barium titanate films grown by molecular beam epitaxy method were performed in grazing incidence geometry. Thin barium titanate film with 8 nm thick was psudomorphic nature. Upper part of the film with 40 nm showed that c-axis lay parallel to the substrate surface and in the middle of the film a-axis lay along the surface. The region, where c-axis lies parallel to the substrate, is quite possible to be 90° domain of BT film.
Conversion Electron/He Ion Yield XAFS of SrTiO3 Thin Films
Authors: Yanase Etsuya , Watanabe Iwao , Harada Makoto , Takahashi Masao , Dake Yoshinori , Hiroshima Yasushi
Published: March 2014

It is known that the dielectric constant of SrTiO3 thin film deposited on a thick substrate decreases with decreasing the thickness. This may be related with local atomic distortion in SrTiO3 thin film. In order to detect the atomic distortion, Sr and Ti K-edge XAFS spectra were measured with a total-conversion electron/He ion-yield (CEY/CIY) apparatus which is easy to build and to operate. We confirmed the validity of our fabricated CEY/CIY apparatus and applied it to XAFS measurement of SrTiO3 thin films. Fourier transforms of XAFS at different thicknesses suggested the local distortion induced by the internal stress in thin films.
In Situ Characterisation of Semiconducting Nanoparticles in Zeolites with XRD, XAFS and SAXS
Authors: Greaves G. N. , Alétru C. , Sankar G. , Catlow C. R. A. , Kempson V. , Colyer L.
Published: March 2014

In situ X-ray Diffraction (XRD), X-ray Absorption Fine Structure (XAFS) spectroscopy and Small Angle X-ray Scattering (SAXS) have been used in conjunction with Diffuse Optical Spectroscopy (DOS) to characterise cadmium oxide particles nucleated within cadmium exchanged sodium zeolite Y treated with sodium hydroxide. The zeolite structure is maintained up to 750°C at which point it collapses to an amorphous intermediate. At lower temperatures the synthesis of cadmium oxide can be followed from cadmium XAFS and SAXS. XAFS identifies the nanocrystalline nature of the product and uv-vis spectroscopy the associated effects of quantum confinement. Microstructural changes evident from SAXS are similar to those occurring when cadmium oxide is synthesised from a hydroxyl gel but nanocrystals are smaller with no increase below 200°C, pointing to incarceration in the zeolite network. Subsequent growth of cadmium oxide may be responsible for the eventual collapse of the zeolite structure at 750°C.
Temperature-Dependent High-Resolution Photoemission Study of Y1-xCaxTiO3
Authors: Arita Masashi , Takeda Yukiharu , Okamura Yoshihiro , Sato Hitoshi , Shimada Kenya , Mamiya Kazutoshi , Namatame Hirofumi , Taniguchi Masaki , Tsubota Masami , Iga Fumitoshi , Takabatake Toshiro
Published: March 2014

Temperature-dependent high-resolution photoemission spectroscopy has been performed on Y1-xCaxTiO3 (x=0.37, 0.39, 0.41) single crystals. Electrons in Ti 3d bands are strongly correlated and clear metal-insulator transition is observed in the photoemission spectra for x=0.39. The spectral shapes of O 2p and Ti 2p states are temperature dependent indicating strong coupling between electronic states and lattice distortion.
Local Distortions of Ideal Perovskite Structure in KNbO3 Revealed by EXAFS
Authors: Bugaev Lusegen A. , Zhuchkov Konstantin N. , Shuvaeva Victoria A. , Rusakova Elizaveta B.
Published: March 2014

The approach for extracting information on the directions and values of atomic displacements from the ideal positions in perovskite type compounds is proposed using EXAFS spectra. It is shown that reliable information can be obtained analysing the discrepancy factor between theoretical and experimental Fourier Transformants (FT) for different models of atomic displacements, generated using the value of averaged atomic displacement, provided by X-ray diffraction. By this approach, the rhombohedral local distortion in cubic phase of KNbO3 is revealed. In tetragonal phase of KNbO3 the minimum of discrepancy factor is obtained in assumption that Nb is shifted by 0.19 Å along [211] direction. These results are shown to be stable under the effects of atoms anharmonicity motion, simulated trough the cumulant expansion by variation of the C4-coeficient value. It is shown that strong difference in Im(FT) remains under all possible C4 values, which makes Im(FT) to be reliable probe for B atom displacement, independent of radial distribution function asymmetry.
Simulation Study of Si–L Total Electron Yield Spectra of Some LiF/Si/LiF Multilayer Using Trial Anisotropic Optical Constants
Authors: Ejima Takeo , Ouchi Katsumi , Watanabe Makoto
Published: March 2014

Simulation study has been made to explain the spectral feature of total electron yield (TEY) spectra of some LiF/Si/LiF multilayer around Si-L edge measured previously for various angles of incidence. The existing formula for the total electron yield has been extended. Optical constants used for the direction perpendicular to the Si layer are those of crystalline Si and those for the direction parallel to the layer is trial ones simulating those of porous Si. The simulated TEY spectra reproduced well the experimental results.
An Electron-Ion Coincidence Spectroscopy Study of Ion Desorption Induced by Core-Electron Transitions of Surfaces
Authors: Mase Kazuhiko , Tanaka Shin-ichiro
Published: March 2014

Ion desorption induced by core-electron transitions is studied for various surfaces by electron-ion coincidence spectroscopy combined with synchrotron radiation. In a study of F+ desorption from Si(100) terminated by fluorine using photoelectron photoion coincidence spectroscopy, the site-selective F+ desorption is directly verified; that is, F+ desorption is induced by Si 2p photoionizations at the ≡SiF, =SiF2, and –SiF3 sites. An Auger electron photoion coincidence study of a CaF2(111) film epitaxially grown on a Si(111) surface also presents direct evidence of F+ desorption, in this case induced by F 1s surface core exciton. These investigations demonstrate that electron-ion coincidence spectroscopy combined with synchrotron radiation is a powerful tool for studying ion desorption induced by core-electron excitations.
Electrochemical Interfaces of Porous Silicon and Ruthenium Dioxide
Authors: You Hoydoo , Chu Yong S. , Lister Tedd E. , Nagy Zoltan
Published: March 2014

Study of electrochemical interfaces of non-metallic electrodes with synchrotron x-ray scattering technique is reported. Our recent in situ investigation of porous silicon during anodic dissolution and of ruthenium dioxide single crystals under reduction/oxidation electrochemical potential cycles are given as examples. In both cases, we show that the structural aspects uncovered by the synchrotron x-ray scattering techniques suggest direct relations to their non-structural properties of importance; for the porous silicon, the relation between the luminescence and pore structures, and for the ruthenium oxide, the relation between the modification of surface structure and the energy storage mechanism.
Mössbauer Optics of Synchrotron Radiation at an Isotope Interface
Authors: Belyakov V. A. , Semenov S. V.
Published: March 2014

Coherent inelastic Mössbauer scattering (CMS) of synchrotron radiation (SR) at an isotope interface (plane interface between two regions differing only in the concentration of the Mössbauer isotope) is investigated theoretically. Main attention is paid to the CIMS component resulting from SR quanta absorption by Mössbauer nuclei accompanying by creation or annihilations of the phonons in sample and following recoilless reemission of Mössbauer quanta which results in the pumping of quanta from the frequency wide SR line to the narrow Mössbauer line. Formulas similar to the well known Fresnel formulas for the reflection and transmission of light at a dielectric interface are obtained for the CIMS at an isotope interface. A similar problem is solved for a plane-parallel sample containing Mössbauer isotope. It is shown that the found specific of CMS can be applied to the problem of Mössbauer filtering of SR.
Scanning Tunneling Microscopy for the Study of the Synchrotron-Radiation Stimulated Processes; Synchrotron-Radiation Stimulated Desorption of SiO2 Films on Si(111) Surface
Authors: Miyamae Takayuki , Urisu Tsuneo , Ucnida Hironaga , Munro Ian H.
Published: March 2014

We have constructed a scanning tunneling microscopy (STM) system for the study of synchrotron radiation (SR) stimulated photochemical reactions. In order to eliminate the vibration and acoustic noise, the entire UHV chamber is mounted on a high-performance air-suspended vibration isolation table and was also covered by the soundproof mat. The mechanisms for SR stimulated desorption of SiO2 thin films on the Si(111) surfaces have been investigated using the STM, low energy electron diffraction (LEED), and Auger electron spectroscopy. An atomically flat and clean Si(111)-(7×7) surface was obtained after two hours SR irradiation at a surface temperature of 700 °C. The STM topograph suggests that the desorption mechanism may be completely different between thermal and SR stimulated desorption of SiO2 film.
Angle-Resolved Photoemission Study of the Clean and Oxygen Covered ZrC(111) Surface
Authors: Edamoto Kazuyuki , Yamazaki Masahiro , Ozawa Ken-ichi , Otani Shigeki
Published: March 2014

Angle-resolved photoemission spectroscopy utilizing synchrotron radiation has been used to study the electronic structure of a ZrC(111) clean surface and the surface covered with oxygen. The spectra of the clean surface show a sharp peak at just below the Fermi level, and the peak is ascribed to the emission from a surface state formed through a charge redistribution around the surface. The polarization dependent measurements show that the surface state is derived from the 4d
z

2 orbital of the surface Zr atom at the Γ̄ point. Oxygen adsorbs dissociatively forming a (1×1) overlayer at the saturation coverage. As the surface is covered with oxygen, the peak from the surface state is quenched and O 2p
z
and 2p
x,y
induced bonding states are formed at 5.3 and 6.0 eV, respectively, at the Γ̄ point. The two-dimensional band structure of the O 2p induced states suggests that the O 2p
x
,2p
y
and 2p
z
states should have nearly the same contribution to the chemisorption bonding on the ZrC(111) surface.
Depth Profile of Delta-doped Semiconductors by X-Ray Reflection Technique
Authors: Jiang Xiaoming , Jia Quanjie , Jiang Zuimin , Iida Atsuo
Published: March 2014

Delta-doping is one of the methods to realize high concentration doping in semiconductors, by which the doped atoms are confined in the thin layer in semiconductor crystals. Sb and Er delta doping layers in silicon crystals were grown at different temperatures by silicon molecular beam epitaxy (MBE). An oxygen ambient was also used in the Er delta doping process. Synchrotron radiation X-ray reflection technique was employed to measure the dopant depth distribution. Results showed that the growth temperature should be below 300°C for obtaining narrow Sb or Er delta doping in order to avoid the surface segregation of Sb or Er atoms. Thermal stability of such delta doped structure was also studied by this technique, no significant change was observed in Sb delta doped Si crystal after annealing at 500°C for 30 min. Besides, suppressing effect of surface segregation of dopant Er by oxygen was investigated. With the oxygen ambient, narrow Er delta doping was realized at growth temperature of 400°C, which was 100°C higher than that in the normal MBE epitaxy.
Temperature Controled Photoelectron Spectroscopic Investigation of Volatile Species on PbS(100) Surface
Authors: Laajalehto Kari , Kartio Ilkka , Heinonen Markku , Laiho Taina
Published: March 2014

A special sample precooling technique has been utilised to preserve thin layers of volatile chemical species on the sample surface in ultra high vacuum conditions for investigation with conventional and synchrotron excited photoelectron spectroscopy. The precooling system has been constructed for the Scienta 300 electron spectrometer at the beam line 51 at MAX I synchrotron laboratory in Lund (Sweden) and it will be transferred to beam line 411 at the new MAX II storage ring. The spectrometer also includes a possibility for continuous temperature control of the sample during the measurement at temperature range 70 K – 450 K. In this work, temperature controlled measuring technique has been applied in a study of electrochemically treated PbS (100) surface. The measured sulfur 2p core level spectra clearly reveal a layer structure of elemental sulfur and metal polysulfides formed during anodic oxidation of PbS in acidic aqueous solution. Similar measuring technique can also be applied, e.g., in studies of adsorption layers on various substrates.
Specific Aspects of X-Ray Diffraction on Statistically Distributed QDs in Perfect Crystal Matrix
Authors: Pavlov Konstantin , Faleev Nikolai , Tabuchi Masao , Takeda Yoshikazu
Published: March 2014

Crystalline (InAs-GaAs)/GaAs (001) multilayer periodic structures containing InAs quantum dots (QDs) have been studied by SR-CTR (Synchrotron Radiation - Crystal Truncation Rod) and RSM (Reciprocal Space Mapping) methods. The appearance of a lateral long-range order in InAs-GaAs QDs has been demonstrated. A qualitative model of investigated structures has been suggested, within which the static Debye-Waller factor has been obtained. Using a new statistical approach considering semidynamical X-ray diffraction allows both the CTR and RSM data to be simulated. The principal parameters of the investigated structures have been determined by means of a fitting procedure.
X-Ray Investigation on the Change of Crystallographic Orientation in Epitaxial Permalloy Induced by Mo Island Edges
Authors: Lee Chih-Hao , Huang J. C. A. , Hu Y. M. , Shih M. C.
Published: March 2014

Epitaxial permalloy thin films were prepared on the sapphire substrates via Mo buffer layer. The structure of epitaxial permalloy film is strongly related to the thickness of the buffer layer. Different preferred orientations has been observed as the thickness of the Mo buffer layer increased from 0 to 20 nm. With the in-plane permalloy[0-11] azimuth always locked on the Al2O3 [0001] direction, the permalloy(111) is the preferred orientation in plane normal direction deposition without Mo layer. The preferred orientation changes to (220) when the Mo layer thickness increases to more than 0.4 nm, and shifts to (211) when the Mo thickness is larger 1 nm. The variation of epitaxial orientation is attributed to the stabilization of permalloy on Mo island edges. As the Mo buffer thickness larger than 10 nm, the permalloy film is developed into a fee twin structure with ID disordered stacking parallel to the underlying Al2O3 [11-20] direction.
CTR and DCXRD Studies of Lateral Ordering of Quantum Dots in Multilayer Periodic Structures
Authors: Faleev Nikolai , Pavlov Konstantin , Tabuchi Masao , Takeda Yoshikazu
Published: March 2014

Containing an array of vertically coupled InAs quantum dots (QDs) in GaAs matrix, multilayer periodic InAs-GaAs structures grown by molecular beam epitaxy, were investigated by SR-CTR (synchrotron radiation-crystal truncation rods) and double-crystal X-ray diffraction (DCXRD). X-ray diffraction is very sensitive to the formation of vertically coupled QDs array, which changes spatial distribution of the scattered radiation. The appreciable elongation of superstructural and substrate spots in lateral directions is explained by occurrence of an additional long-range lateral ordering of scattering objects and quasi-periodic deformation relief in the top GaAs layer. Perfect coherently-connected InAs and GaAs clusters are introduced as a novel qualitative structural model of scattering layers. Based on this model the main features of spatial distribution of diffracted intensity have been explained.
Study of Pt/C X-Ray Multilayer Structure as a Function of Layer Perid Using X-Ray Scattering
Authors: Lodha Gyanendra , Paul Amitash , Vitta Satish , Gupta Ajay , Nandedkar Rajendra , Yamashita Koujun , Kunieda Hideyo , Tawara Yozuru , Tamura Keisuke , Haga Kazutoshi , Okajima Takashi
Published: March 2014

Pt/C x-ray multilayer, with varying period lengths d, ranging from 4.7 nm to 3.5 nm were made by dc magnetron sputtering under identical deposition conditions. The Pt layer thickness in all the cases was maintained at a nominal value of 0.37d and a total of 20 layer periods were deposited in each case. Since the morphology in the interface plane and along the growth direction is important for imaging applications, the dependence of this on the layer period has been investigated using x-ray scattering. The grazing incidence x-ray scattering technique has been used to study both the specular and diffuse scattering behaviour of these multilayer structures. The interface roughness was determined from the specular reflectivity measured over a large momentum transfer range using both 0.154 nm and 0.834 nm wavelength x-rays. The interface roughness was found to vary from ∼ 0.32 nm to 0.40 nm with decreasing period. The diffuse component of scattering on the other hand was found to decrease with a decrease in layer period. The atomic ordering in the individual layers studied using high angle x-ray diffraction shows clearly the presence of crystallinity in the Pt layers, independent of the layer period.
CTR Scattering Derived from Dynamical Theory of Diffraction
Authors: Kashihara Yasuharu , Kimura Shigeru
Published: March 2014

“X-ray Crystal Truncation Rods Scattering” is interpreted by the diffraction far from the Bragg peaks obtained from the dynamical theory of diffraction. In the Ewald construction that is used in the kinematical theory, the intensity of the Bragg reflection obtained from the dynamical theory is distributed in a rod shape that is elongated through each Bragg point in the direction perpendicular to the crystal surface. The intensities, therefore, are represented as a function of the distance between the observation point in reciprocal space and the Bragg point. We calculate the intensity around the 111 reciprocal lattice point of Si(001) for the various diffraction geometries – the symmetric diffraction geometry, the constant incident geometry, and the constant exit angle geometry.
Ordered Structure in Buried Oxide Layers of SOI Wafers
Authors: Shimura Takayoshi , Hosoi Takuji , Ejiri Riho , Umeno Masataka
Published: March 2014

We have investigated the existence of ordered structure in buried oxide layers of SOI (silicon on insulator) wafers. Two kinds of SOI wafers, bonded and SIMOX wafers, were examined by x-ray diffraction technique. As the results, the diffraction streaks perpendicular to the interfaces were found at the middle of the reciprocal lattice points of Si for the SIMOX wafer, while no clear diffraction evidence indicating some structural property was observed for the bonded wafer. This means that there exists an ordered structure in the buried oxide layer of SIMOX wafers, having epitaxial relationship with the Si substrate.
X-Ray Diffraction Studies of the InSb(001) Surface
Authors: Jones Nigel , Norris Colin , Nicklin Christopher L. , Johnson Andrew D. , Bennett Stephen L.
Published: March 2014

The (001) surface of the III-V alloy semiconductors exhibits many reconstructions with large unit meshes. The appearance of a given reconstruction depends on the processing conditions and, in particular on the stoichiometry at the surface. A surface X-ray diffraction study of the atomic structure of the Sb-rich c(4×4) and the In-rich c(8×2) surfaces is described which allows for the first time, a detailed atomic model of these important reconstructions to be derived. The basic units consist of groups of Sb dimers and rows of In atoms on top of an Sb terminated bulk. The local bonding is similar to that found in rhombahedral Sb and tetragonal In bulk structures. The results explain why the Sb rich surface is used as a starting point for the growth and are relevant to other III-V (001) surfaces.
XANES and XPS Analyses of Silicon Irradiated by Deuterium Ions
Authors: Yoshida Tomoko , Tanabe Tetsuo , Yoshida Hisao , Yazawa Yoshiteru , Hara Takanobu , Sakai Mikio , Yamamoto Hiroyuki , Baba Yuji
Published: March 2014

XANES and X-ray photoelectron spectra (XPS) using synchrotron radiation as a X-ray source were applied for analysis of silicon crystalline irradiated by 5 keV deuterium ions. Si K-edge XANES spectra recorded either by a photocurrent or electron yield modes clearly showed a new absorption peak in addition to the absorption due to surface SiO2. In Si Is XPS spectra, on the contrary, no clear peak or shoulder was detected except SiO2 species. Taking into account that Si K-edge XANES reflects the electron transition from Si 1s to np (empty bound state), the new absorption peak is very likely caused by the generation of localized electronic bond between Si and D in the vicinity of the damaged region in the irradiated Si.
Electronic and Structural Analysis of 6H-SiC(0001̄)3×3 Reconstructed Surface
Authors: Sasaki Hiroshi , Jikimoto Tamotsu , Kinoshita Akimasa , Hirai Masaaki , Kusaka Masahiko , Iwami Motohiro , Nakata Toshitake
Published: March 2014

The 6H-SiC(0001̄) C 3×3 reconstructed surface was studied by PES using synchrotron radiation, LEED and AES. This surface with contamination free was obtained by ex-situ surface treatment and annealing at 900°C without Si flux in the UHV. The p-p height ratio of AES signals, Si (LVV) / C (KLL), was measured as a function of annealing temperature for (0001̄) surfaces to show a clear decrease with increasing temperature above 900°C. Discussion was given for the relation of this ratio with reconstructed surfaces. It was found that the photoemission spectra in the valence band region had the structure located at 0.9 eV below Fermi level. The signal should be originated from a surface state.
Photoabsorption and MXCD in Photoemission Microscopy for Characterization of Advanced Materials
Authors: Fecher Gerhard H. , Hwu Yeukuang
Published: March 2014

We used imaging spectromicroscopy to characterise micro-patterned thin films of magnetic materials like FeNi alloys on Silicon. To investigate devices built from complex materials we applied element-sensitive photoelectron emission microscopy (PEEM). Information about the chemical composition of the imaged sample can be obtained by PEEM via tuning the photon energy to X-ray absorption edges. One aim of our work was to observe oxygen related defects and changes in the composition effecting the physical properties of the materials. The use of circularly polarised photons allows us to image magnetic domains by making use of the magnetic circular dichroism (MXCD).
Combined Chemical Microanalysis Using SAM and X-PEEM
Authors: Grahneis Werner , Ziethen Chistian , Fecher Gerhard H. , Schönhense Gerd
Published: March 2014

Both, PEEM (Photoemission Microscopy) and SAM (Scanning Auger Microprobe) are surface sensitive techniques providing spatially resolved chemical analysis. We compare these techniques and present results on thin High Temperature Superconductor films.
The X-PEEM makes use of tuneable monochromatised soft X-rays from a synchrotron radiation source to excite electrons from core levels. A higher secondary electron yield is observed when tuning the source above one of the characteristic absorption edges. These true secondaries are detected with the electron microscope in parallel imaging mode. Therefore, PEEM gives besides the imaging additional information on the chemical bonding and its local order making use of NEXAFS and EXAFS spectroscopies.