J. Mizuki

Pseudomorphic growth of Pd monolayer on Au(111) electrode surface

Abstract The surface structure of a Pd layer electrochemically deposited onto Au(111) from PdCl 2− 4 solution has been studied by surface X-ray diffraction. By combining the measurements of the specular and non-specular rod profiles, both in-plane and out-of-plane structures have been determined. On the Au(111) electrode surface, Pd occupies the cubic closest packing site and forms a pseudomorphic smooth monolayer. The formation of the stable Pd overlayer is explained by the lifting of the surface reconstruction of the Au substrate. The Pdue5f8Au bond length at the Pd/Au(111) interface has been found to be 2.82xa0A, which is close to the sum of the atomic radii of Pd and Au in each bulk.

Structure and protective performance of atmospheric corrosion product of Fe–Cr alloy film analyzed by Mössbauer spectroscopy and with synchrotron radiation X-rays

Abstract The structure of atmospheric corrosion product of Fe–5 mass%Cr alloy film has been examined by using synchrotron radiation X-rays and γ-rays for Mossbauer spectroscopy. The relationship between the position of Cr 3+ in the atomic arrangement of the rust crystal and the protective performance of the rust layer is discussed. It was found that the rust layer of the Fe–Cr alloy film contains a large amount of ultrafine Cr–goethite. By analyzing the X-ray absorption fine structure at Cr K-edge of the rust layer, we can conclude that Cr 3+ is positioned in the double chains of vacant sites in the network of FeO 3 (OH) 3 octahedra in the goethite crystal. This Cr 3+ site might explain the protective performance, owing to dense aggregation of fine crystals with cation selectivity, of the Cr–goethite.

Momentum Dependence of Charge Excitations in the Electron-Doped Superconductor Nd1:85Ce0:15CuO4: A Resonant Inelastic X-Ray Scattering Study

We report a resonant inelastic x-ray scattering (RIXS) study of charge excitations in the electron-doped high-T(c) superconductor Nd1.85 Ce0.15 CuO4. The intraband and interband excitations across the Fermi energy are separated for the first time by tuning the experimental conditions properly to measure charge excitations at low energy. A dispersion relation with q-dependent width emerges clearly in the intraband excitation, while the intensity of the interband excitation is concentrated around 2 eV near the zone center. The experimental results are consistent with theoretical calculation of the RIXS spectra based on the Hubbard model.

A novel spectroelectrochemical cell for in situ surface X-ray scattering measurements of single crystal disk electrodes

A newly designed spectroelectrochemical cell was constructed for surface X-ray scattering (SXS) to study single crystal electrodes. Electrochemical characteristics of a specific face of a single crystal electrode can be investigated in the meniscus mode, and SXS measurement can be easily carried out using the spectroelectrochemical cell. The usefulness of the present cell was demonstrated by studying the electrochemical deposition of thin Pd layers on Au(111) and Au(100) that require precise amounts of Pd deposits.

Stacking-fault-induced intermediate structure in bismuth titanate

We observed an intermediate structure during the recrystallization process from the amorphous state of Bi4Ti3O12 prepared by rapid quenching. The intermediate structure which appears during the recrystallization process consists of two phases; one is pyrochlore Bi2Ti2O7 phase and the other is a stacking-fault-induced structure under the excessive Bi condition. The microstructure of the stacking-fault-induced structure was investigated by synchrotron x-ray diffraction. In the case of a large number of Bi2O2, some are inserted between the pseudoperovskite layers of Bi4Ti3O12, and a nonstoichiometric Bi2WO6-like structure is stabilized.

Mott gap excitations in twin-free YBa2Cu3O7-delta (Tc=93 K) studied by resonant inelastic x-ray scattering.

Mott gap excitations in the high-Tc superconductor of the optimal doped YBa2Cu3O7-d (Tc = 93 K) have been studied by the resonant inelastic x-ray scattering method. Anisotropic spectra in the ab-plane are observed in a twin-free crystal. The excitation from the one-dimensional CuO chain is enhanced at 2 eV near the zone boundary of the b* direction, while the excitation from the CuO2 plane is broad at 1.5-4 eV and almost independent of the momentum transfer. Theoretical calculation based on the one-dimensional and two-dimensional Hubbard model reproduces the observed spectra by taking the different parameters of the on-site Coulomb energy. The fact of the Mott gap of the CuO chain site is much smaller than that of CuO2 plane site is observed for the first time.

In situ monitoring of internal strain and height of InAs nanoislands grown on GaAs(001)

A monitoring technique for molecular beam epitaxial growth of InAs∕GaAs(001) nanoislands is presented. With the help of synchrotron radiation, x-ray diffraction intensity mapping in reciprocal space has been measured during growth. The internal strain distribution and height of the Stranski-Krastanov islands were monitored at a temporal resolution of 9.6s. The relaxation process of internal strain inside the Stranski-Krastanov islands displayed significant dependence on the growth temperature.

An inelastic X-ray scattering spectrometer for materials science on BL11XU at SPring-8

Abstract An inelastic X-ray scattering spectrometer on the beamline BL11XU at the SPring-8 is described. The typical energy resolution and energy transfer are 0.1–1xa0eV and ∼30xa0eV, respectively. The main aim of this spectrometer is the measurement of electronic excitations, such as charge-transfer excitation and interband transition, especially using resonant X-ray scattering. As a test experiment, the resonant X-ray scattering spectra of LaMnO 3 including Mn Kβ 5 emission are given.

Coverage of the Cd Underpotential Deposited Layer Formed on an Au(111) Substrate Effect of the Electrolytic Conditions

The surface-normal structure of a Cd layer formed on an Au(111) substrate using underpotential deposition (UPD) in a sulfuric acid solution has been investigated by specular X-ray reflectivity measurements. The measurements were carried out for the Cd UPD layers which were formed at the first and second UPD potential in electrolytic solutions of I mM CdSO 4 with 10 mM and 100 mM H 2 SO 4 . In all cases, a Cd atomic layer is positioned on the Au(111) surface, which is similar to the reconstructed structure, and also a sulfuric acid anion layer is positioned on the Cd atomic layer. Contrary to results of the previous literature, the Cd coverage of the UPD layer depends not on the UPD potential but on the concentration of H 2 SO 4 . The coverage of the Cd atoms increases from approximately 0.50 to approximately 0.60 monolayer as the concentration of H 2 SO 4 increases from 10 to 100 mM, and the coverage of the sulfuric acid anions is approximately half the Cd coverage.

Theory and experiment of orbital excitations in correlated oxides

Orbital excitations in orbital-ordered transition metal oxides are investigated theoretically and experimentally. Characteristic differences in the collective orbital excitations, termed orbital waves, between the eg and t2g systems are clarified. As a probe to detect the orbital excitations, the scattering processes for the Raman scattering and the resonant and non-resonant inelastic x-ray scatterings are proposed and their scattering cross-sections are calculated. The orbital excitations in hole-doped and undoped manganites are examined experimentally by using resonant inelastic x-ray scattering. The obtained experimental results are compared with the theoretical calculations.