Techniques for inelastic X‐ray scattering with μeV‐resolution

A new spectroscopic technique is introduced that allows tuning of a eVwide beam of synchrotron radiation over a range of a few meV. It relies on nuclear resonant scattering that is subject to the Doppler effect in high speed rotary motion. Two mechanisms are discussed how to extract the resonantly scattered radiation out of the broad band of synchrotron radiation: (a) grazing incidence reflection from a rotating disk in combination with a polarization filtering technique and (b) deflection of resonantly scattered radition via the recently discovered Nuclear Lighthouse Effect. Implications for inelastic Xray scattering and elastic nuclear resonant scattering are discussed.     

The study of orbital ordering with resonant x‐ray scattering

Japan has nearly 50 years of history in synchrotron radiation (SR) research and has realized the importance of synchrotron radiation in science advancement since the very beginning. As a result, many SR facilities have been constructed. Today, there are eight SR facilities in operation and three facilities under construction in Japan. Figure 1 shows the location of these facilities with their opening years. Japan has built the world's largest storage ring with circumference of 1.4 km (SPring-8) and the world's smallest ring with circumference of 3 m (Ritsumeikan SRC).     

Self—assembly behaviour of amphiphilic diblock copolymer in selective solvents studied by synchrotron small—angle x—ray scattering

The aggregation behaviour of styrene-vinyl benzoic acid (PS_m-b-PVBA_n) amphiphilic diblock copolymers in selective solvents with different m and n was investigated by synchrotron small-angle x-ray scattering (SAXS). We have carried out a detailed analysis of scattering intensity, dimension, shape and microstructure of the diblock copolymers of narrow distribution in water, methanol, ethanol and isopropanol selective solvents, respectively. We have found that the aggregation behaviour of the copolymer depends on the nature of the solvent and the micelle forms flat disc objects with the ratio of radius ω=0.4. The average radius gyration R_g of the copolymer decreases as solvents change from isopropanol to ethanol and to methanol, and increases with increasing pH in aqueous solution, but decreases with the addition of CoCl_2 in ethanol solvent. The scattering intensity of diblock copolymer micelle follows I(h)∝h^{-α} in different selective solutions, suggesting that the PS_m-b-PVBA_n coils have self-similar structure behaviour or a fractal structure in the selective solvents. All of these revealed that the aggregation behaviour of the diblock copolymer changes dramatically with experimental condition in the selective solvent. The increase of mass fractal dimension (D_m) from 2.12 to 2.47 indicates that the copolymer chain changes from a swollen coil to a rather compact disc in the course of changing solvents, decreasing surface fractal dimension (D_s) from 2.98 to 2.58 indicates that the copolymer micelle change from a rather rough surface to a smooth form in the course of increasing pH in aqueous solutions, and increasing D_m and D_s from 2.29 to 2.35 and 2.70 to 2.90, respectively, indicates the shrinkage of copolymer micelle to a rather compact and rough disc form by adding CoCl_2 in ethanol solvents.     

Spectrophotometric and 27‐Al NMR Characterization of Aluminum(III) Complexes with l‐Histidine

Abstract

The complex formation between l‐histidine (HHis) and aluminum(III) ion in water solutions was studied by UV spectrophotometric and 27‐Al NMR measurements at 298 K. UV spectra were measured on solutions in which the total concentration of histidine was from 15.0 to 50.0 mmol/dm³ and the concentration ratio of histidine to aluminum was varied from 3∶1 to 10∶1 in the pH range between 4.2 and 6.0. The spectra were taken in the wavelength interval 240–340 nm. Nonlinear least‐squares treatment of the spectrophotometric data indicates the formation of the complexes Al(HHis)³⁺, Al(His)²⁺, Al(HHis)His²⁺, and Al₂(OH)His⁴⁺ with the overall formation constants β_p,q,r: log β_1,1,1=11.90±0.04, log β_1,1,0=7.25±0.08, log β_1,2,1=20.1±0.1, and log β_2,1,1=5.92±0.12 (p, q, r are stoichiometric indices for metal, ligand, and proton, respectively). ²⁷Al‐NMR spectra were taken on solutions with the concentration of aluminum 50 mmol/dm³ and that of histidine 250 mmol/dm³. In the pH interval 5.0–6.1, two resonances at 9.5 ppm and 12.0 ppm were assigned to Al(HHis)²⁺ and Al(HHis)(His)²⁺ (or Al(OH)(HHis)₂ ²⁺), respectively.     

Structural Characterization of RF‐Sputtered a‐C:N Thin Films by Raman,IR, and X‐ray Reflectometry Spectroscopies

Abstract

Amorphous carbon nitride thin films (a‐C:N) were deposited from a carbon target, at room temperature onto silicon substrates, by reactive RF sputtering in a gas mixture of argon and nitrogen. The structural properties of these films have been studied by Raman, infrared (IR), and X‐ray reflectometry spectroscopies. Both the IR and Raman spectra of the a‐C:N films reveal the presence of C–C, C?C, C?N, and C≡N bonding types. The Raman spectra analysis shows, an increase of the C≡N triple bonds content when the concentration of nitrogen C(N₂) in the gas mixture is increased. The Raman intensities ratio between the disorder (D) and graphitic (G) bands increases with C(N₂) suggesting an increased disorder with the incorporation of nitrogen in the carbon matrix. The effect of C(N₂) on the density of a‐C:N films was also investigated by X‐ray reflectometry measurement. The increase of the nitrogen concentration C(N₂) was found to have a significant effect on the density of the films: as C(N₂) increases from 0 to 100%, the density of the a‐C:N films decreases slightly from 1.81 to 1.62 g/cm³. The low values of density of the a‐C:N films were related (i) to the absence of C–N single bonds, (ii) to the increase of disorder introduced by the incorporation of nitrogen in the carbon matrix, and (iii) to the presence of the bands around 2350 cm^?1 and 3400 cm^?1 associated with the C–O bond stretching modes and the O–H vibration, respectively, suggesting a high atmospheric contamination by oxygen and water. The presence of these bands suggests the porous character of the studied samples.     

Third-order optical nonlinearities of Zn_(1-x)Mg_xO thin films

Materials with large optical nonlinearities have receivedincreased attention in the past years because they arecrucial for the development of components for all-opticalsignal processing, and have many potential applicationsin electro-optic and integrated optical devices, nonlinearoptical switching devices and real-time coherent opticalsignal processors[1-3]. ZnO, as a representatively wideband gap semiconductor, triggers research interestingon optical nonlinear-response in recent years, owning…     

Achievement of soft－X－ray laser with nearly saturated intensity and minimum divergence angle～1 mrad

Ａｃｈｉｅｖｅｍｅｎｔ ｏｆ ｓｏｆｔ－Ｘ－ｒａｙ ｌａｓｅｒ ｗｉｔｈ ｎｅａｒｌｙ ｓａｔｕｒａｔｅｄ ｉｎｔｅｎｓｉｔｙ ａｎｄ ｍｉｎｉｍｕｍ ｄｉｖｅｒｇｅｎｃｅ ａｎｇｌｅ～１ｍｒａｄ￥ＷＡＮＧＳｈｉｊｉ；ＧＵＹｕａｎ；ＺＨＯＵＧｕａｎｌ...     

Deposition of ZnO thin films on (100) γ-LiAlO_2 substrate

The resurgence in the study of ZnO continues. The now ready availability of good-quality single crystals and films[1,2] and discovery of lasing action in the materials[3] have generated new life in an old material. A direct semi- conductor with a gap energy of 3.3 eV[4], ZnO is in the position of being able to offer a challenge to GaN in the blue laser market[5]. The advantages of ZnO are the high quality of the material and the large exciton bind- ing energy (60 meV). The large exciton bi…     

Hall effect of FeTe and Fe(Se1–xTex) thin films

The Hall effect is investigated in thin-film samples of iron–chalcogenide superconductors in detail. The Hall coefficient (R_H) of FeTe and Fe(Se_1–xTe_x) exhibits a similar positive value around 300 K, indicating that the high-temperature normal state is dominated by hole-channel transport. FeTe exhibits a sign reversal from positive to negative across the transition to the low-temperature antiferromagnetic state, indicating the occurrence of drastic reconstruction in the band structure. The mobility analysis using the carrier density theoretically calculated reveals that the mobility of holes is strongly suppressed to zero, and hence the electric transport looks to be dominated by electrons. The Se substitution to Te suppresses the antiferromagnetic long-range order and induces superconductivity instead. The similar mobility analysis for Fe(Se_0.4Te_0.6) and Fe(Se_0.5Te_0.5) thin films shows that the mobility of electrons increases with decreasing temperature even in the paramagnetic state, and keeps sufficiently high values down to the superconducting transition temperature. From the comparison between FeTe and Fe(Se_1–xTe_x), it is suggested that the coexistence of ‘itinerant’ carriers both in electron and hole channels is indispensable for the occurrence of superconductivity.     

Growth of thin films of TiN on MgO(100) monitored by high-pressure RHEED

Reflection high-energy electron diffraction (RHEED) operated at high pressure has been used to monitor the initial growth of titanium nitride (TiN) thin films on single-crystal (100) MgO substrates by pulsed laser deposition (PLD). This is the first RHEED study where the growth of TiN films is produced by PLD directly from a TiN target. At the initial stage of the growth (average thickness ∼2.4 nm) the formation of islands is observed. During the continuous growth the islands merge into a smooth surface as indicated by the RHEED, atomic force microscopy and field emission scanning electron microscopy. These observations are in good agreement with the three-dimensional Volmer–Weber growth type, by which three-dimensional crystallites are formed and later cause a continuous surface roughening. This leads to an exponential decrease in the intensity of the specular spot in the RHEED pattern as well.     

Diffraction of X rays at a Bragg angle of π/2 (Back reflection) with consideration of multiwave effects

The energy dependence of the back reflectivity in the dynamical diffraction of x rays at a Bragg angle of π/2 (back diffraction) in perfect crystals of cubic symmetry (silicon) is investigated theoretically. In this case strict backscattering is realized only under the conditions of multiple diffraction. The features of the influence of multiple diffraction on back reflection in the energy range near the nuclear resonance radiation energy of 14.41 keV for ⁵⁷Fe nuclei, specifically in the six-wave case, including the silicon (1,9,9) reflection (with an energy of 14.57 keV), which can be investigated experimentally with high energy resolution (1 meV) using synchrotron radiation and a monochromator developed for nuclear resonant absorption, are thoroughly studied. It is shown that the back reflectivity observed under the conditions of multiple diffraction has several maxima on the plot of its energy dependence with a value at each maximum smaller than half, in contrast to two-wave diffraction, where there is one maximum with a value close to unity. Zh. éksp. Teor. Fiz. 116, 940–952 (September 1999)     

Crystallisation of magnetron sputtered amorphous Si1− x C x films (x = 1/3) studied by grazing incidence X-ray diffractometry

The crystallisation of amorphous Si_{1? x} C _x films (x = 1/3) produced via magnetron sputtering on silicon substrates was investigated. Grazing incidence X-ray diffractometry was used to analyse the crystalline precipitates obtained after annealing at temperatures between 1200°C and 1350°C. After annealing times of 15 h at 1200°C and 15 h at 1350°C, crystallisation of SiC is complete. The average crystallite size, d, was determined using the Scherrer equation. The rate constants for the initial growth of the crystallites were determined by straight line fits in the d ? t diagrams (t being the annealing time), which obey the Arrhenius law. The activation enthalpy of 4.0 ± 0.7 eV is, within error limits, the same as that found for the growth of silicon carbide crystallites in magnetron sputtered Si_{1? x} C _x films (x = 1/2).     

Preparation and characterization of biodegradable poly(ε-caprolactone)-based gel polymer electrolyte films

Biodegradable polymer electrolyte films based on poly(ε-caprolactone) (PCL) in conjunction with lithium tetrafluoroborate (LiBF₄) salt and 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF₄) ionic liquid were prepared by solution cast technique. The structural, morphological, thermal, and electrical properties of these films were examined using X-ray diffraction (XRD), optical microscopy (OM), differential scanning calorimetry (DSC), and impedance spectroscopy. The XRD and OM results reveal that the pure PCL possesses a semi-crystalline nature and its degree of crystallinity decreases with the addition of LiBF₄ salt and EMIMBF₄ ionic liquid. DSC analysis indicates that the melting temperature and enthalpy are apparently lower for the 40 wt% EMIMBF₄ gel polymer electrolyte as compared with the others. The ambient temperature electrical conductivity increases with increasing EMIMBF₄ concentration and reaches a high value of ～2.83?×?10^?4 S cm^?1 for the 85 PCL:15 LiBF₄ + 40 wt% EMIMBF₄ gel polymer electrolyte. The dielectric constant and ionic conductivity follow the same trend with increasing EMIMBF₄ concentration. The dominant conducting species in the 40 wt% EMIMBF₄ gel polymer electrolyte determined by Wagner’s polarization technique are ions. The ionic conductivity of this polymer electrolyte (～2.83?×?10^?4 S cm^?1) should be high enough for practical applications.     

Micro—structural analysis of YBa2Cu3O7—x thin films grown on different substrates by X—ray techniques

YBa2Cu3Ox(YBCO) thin films grown on different substrates with and/or without Eu2CuO4(ECO) buffer layer were investigated by X-ray wide angle diffraction,reflection,diffuse scattering and topography.Theresults show that for the yttria stabilized ZrO2(YSZ) substrate,the presence of an ECO buffer layer improves the crystalline quality of the YBCO film,while a negative effect is observed for the SrTiO3(STO) substrate.The lateral correlation length for a sample grown on a YSZ substrate with ECO buffer Layer is much greater than grown on an STO subetrate.The STO substrate used has mosaic structure.2001 Elsevier Science B.V.All rights reserved.     

Synthesis and Characterization of Novel Poly(1‐Naphthylamine)‐Montmorillonite Nanocomposites Intercalated by Emulsion Polymerization

Nanocomposites of montmorillonite (MMT) with poly(1‐naphthylamine) (PNA) is investigated for the first time by emulsion polymerization using three different oxidants. Polymerization of PNA was confirmed by Fourier transformation infrared (FT‐IR) as well as UV‐visible spectra. The in situ intercalative polymerization of PNA within MMT layers was confirmed by FT‐IR, X‐ray diffraction, conductivity; scanning electron microscopy (SEM) as well as transmission electron microscopy studies. X‐ray diffraction revealed intercalated as well as exfoliated structures of PNA/MMT nanocomposites, which were compared with the reported polyaniline‐MMT nanocomposites. It was found that the increase in the concentration of PNA in the interlayer galleries of MMT led to destruction of the layered clay structure resulting in exfoliation of the nanocomposite. Conductivity of the nanocomposites was found to be in the range of 10^?3 to 10^?2 S cm^?1 which was found to be higher than the ones reported for polyaniline‐clay nanocomposites as well as PEOA‐OMMT nanocomposites at similar concentrations of intercalated species. The morphology of PNA/MMT nanocomposites was found to be governed by the nature of the oxidant used.     

Effect of 90° domain walls on the low-field permittivity of PbZr(0.2)Ti(0.8)O3 thin films

We report on the contribution of 90° ferroelastic domain walls in strain-engineered PbZr(0.2)Ti(0.8)O(3) thin films to the room-temperature permittivity. Using a combination of phenomenological Ginzburg-Landau-Devonshire polydomain thin-film models and epitaxial thin-film growth and characterization, the extrinsic or domain wall contribution to the low-field, reversible dielectric response is evaluated as a function of increasing domain wall density. Using epitaxial thin-film strain we have engineered a set of samples that possess a known quantity of 90° domain walls that act as a model system with which to probe the contribution from these ferroelastic domain walls. We observe a strong enhancement of the permittivity with increasing domain wall density that matches the predictions of the phenomenological models. Additionally, we report experimentally measured bounds to domain wall stiffness in such PbZr(0.2)Ti(0.8)O(3) thin films as a function of domain wall density and frequency.     

Study of solid-state reactions and order-disorder transitions in Pd/α-Fe(001) thin films

The formation of the hard-magnetic ordered L1₀-FePd phase in thin bilayer Pd/α-Fe(001) films has been experimentally studied. Solid-state reactions initiated by thermal heating in bilayer Pd/α-Fe(001) films with a thickness of 50–60 nm (the atomic ratio Pd: Fe ≈ 50: 50) separated from the substrate have been studied using the in situ electron diffraction methods. It has been shown that the solid-state reaction between the palladium and iron layers in Pd/α-Fe(001) starts at 400°C with the formation of the disordered Fe-Pd phase. At 480°C, the ordered L1₀-FePd phase is formed. The order-disorder phase transition has been studied. It has been established that the transition of the ordered L1₀-FePd phase to the disordered FePd phase starts at 725°C. At 740°C, only the disordered FePd phase is present over the whole volume of the film. The observed temperature of the order-disorder phase transition is shifted from the equilibrium value by 35°C to higher temperatures. This effect is assumingly associated with the higher concentration of palladium atoms at the boundaries of the Fe-Pd crystal grains owing to the grain-boundary adsorption.     

Near-infrared lateral photovoltaic effect of epitaxial LaTiO--_(3+δ) films under high pressure

A lateral photovoltaic effect(LPE) is discovered in an La TiO_(3+δ)film epitaxially grown on a(100) Sr TiO_3 substrate. Under the illumination of a continuous 808 nm laser beam that is focused on the La TiO_(3+δ)film through the Sr TO3 substrate, the open-circuit photovoltage depends linearly on the illuminated position. The sensitivity of the LPE can be modified by the bias current. The La TiO_(3+δ)film shows a stable photoelectric property under the high pressure, up to 9 MPa. These results indicate that the La TiO_(3+δ)films can give rise to a potentially photoelectronic device for near-infrared position-sensitive detection in high-pressure environments.