T. Nagatomi

Catalysis of Nickel Ferrite for Photocatalytic Water Oxidation Using [Ru(bpy)3]2+ and S2O82–

Single or mixed oxides of iron and nickel have been examined as catalysts in photocatalytic water oxidation using [Ru(bpy)(3)](2+) as a photosensitizer and S(2)O(8)(2-) as a sacrificial oxidant. The catalytic activity of nickel ferrite (NiFe(2)O(4)) is comparable to that of a catalyst containing Ir, Ru, or Co in terms of O(2) yield and O(2) evolution rate under ambient reaction conditions. NiFe(2)O(4) also possesses robustness and ferromagnetic properties, which are beneficial for easy recovery from the solution after reaction. Water oxidation catalysis achieved by a composite of earth-abundant elements will contribute to a new approach to the design of catalysts for artificial photosynthesis.

Quantitative measurement of surface potential and amount of charging on insulator surface under electron beam irradiation

Surface potential and the amount of charging on an insulator surface under electron beam irradiation have been quantitatively measured. For these measurements, a special sample holder was developed. The surface potential was measured using a secondary electron method. The measurement of the surface potential revealed that the sample behaves as a resistor, enabling the present technique to be applied for mapping microarea resistance. The results of measuring the amount of charging revealed that the amounts of charging obtained with different beam currents are the same in spite of different surface potentials. This strongly suggests that the charging phenomenon depends on the distribution of the charge trapping sites.

Energy Loss Functions For Electron Energy Loss Spectroscopy

Losses to surface excitations affect experimental data in several different kinds of spectroscopies and have been considered in detail by various workers. We discuss and compare calculations using commonly assumed response functions. The boundary (begrenzung) effect, originating in the orthogonality of surface and bulk eigenmodes, manifests interesting interference in the loss functions. The variation of static electron density in the selvage of a metal is known to affect the dispersion of surface excitations. The effect of this structure on energy loss spectra is studied. Analytical forms of the kind studied can be employed in practical data analysis if parameterized to correspond with more rigorous, but time-consuming, numerical results such as those found from density functional methods.

Determination of effective energy loss functions and x-ray photoelectron spectroscopy source functions for Si 2p photoelectrons from clean Si(111), oxygen-adsorbed Si(111) and SiO2 surfaces

Effective energy loss functions for Si 2p photoelectrons were determined for the thermally cleaned Si(111), oxygen-adsorbed Si(111) and SiO2 surfaces by the analysis of the reflection electron energy loss spectroscopy (REELS) spectra using the extended Landau theory. The background subtraction of the Si 2p x-ray photoelectron spectroscopy (XPS) spectra using these effective energy loss functions has enabled the XPS source functions to be derived with considerable effectiveness. This result has indicated that the effective energy loss functions derived for the clean Si(111) surface are significantly affected by the oxygen adsorption and the XPS source functions from the clean and oxygen-adsorbed Si(111) surfaces show a small hump due to the chemical shift by the oxygen adsorption appearing at the tail of the lower kinetic energy side of the Si 2p peak from the oxygen-adsorbed Si surface. On the SiO2 surface, the analysis of the REELS spectrum has yielded the effective energy loss function reflecting the fi...

Hard x-ray phase contrast imaging using a tabletop Talbot–Lau interferometer with multiline embedded x-ray targets

We demonstrate hard x-ray phase contrast imaging (XPCI) using a tabletop Talbot-Lau interferometer in which the x-ray source and source grating are replaced with an x-ray source with multiline metal targets embedded in a diamond substrate. This source realizes an array of linear x-ray sources of a few micrometers width without fabrication difficulty because of the shallow penetration depth of electrons irradiated to the metal targets. This enhances the coherence of x rays from each linear source and allows XPCI within 45 cm source-detector distance under 1.2 W input power for 8 keV x rays.

Monte Carlo simulation of background in AES: a comparison with experiment

Monte Carlo simulations of the energy distribution of backscattered electrons including cascade secondary electrons have been carried out. This calculation yields the background observed in direct mode by AES. We found that, based on a dielectric model of electron inelastic scattering and secondary excitation, the simulation describes very well the background of the experimental EN(E) spectra for Si, Cu, Ag and Au measured with a novel cylindrical mirror analyzer which has been developed by Goto for providing standard AES spectra. The results reveal that the Monte Carlo simulation has potentiality for providing an intimate insight into more accurate theoretical background for the quantitative AES study and for establishing the data base of standard spectra.

Effective energy-loss functions for oxygen-adsorbed amorphous silicon surfaces

Effective energy-loss functions were derived for oxygen-adsorbed amorphous silicon surfaces from a reflection electron energy-loss spectroscopy analysis based on the extended Landau theory. This study has revealed that the intensity of the surface-plasmon-loss peak for a clean surface decreases and its peak position shifts towards the lower-energy losses as oxygen exposure proceeds (⩽1000 L). To understand the above behavior of the surface-plasmon-loss peak, the distribution of the energy losses was calculated using the hydrodynamic model. The decrease and shift of the surface-plasmon-loss peak has been described with considerable success by assuming that the quasifree static electron density in the vicinity of the silicon surface decreases as oxygen adsorption proceeds owing to oxygen’s high electron affinity.

Surface Structure of Sc-O/W(100) System used as Schottky Emitter at High Temperature

The surface characterization of the Sc–O/W(100) system was performed by low-energy electron diffraction, Auger electron spectroscopy and work function measurement at 1500 K, the operating temperature of the Sc–O/W(100) emitter. For this, a sample holder with a heater was newly developed. In addition, the differential measurement method was applied to low-energy electron diffraction. The present results reveal that the p(1×1)-Sc–O/W(100) surface having a work function of 3.2 eV is formed by heating at 1700 K.

Initial Stage of Oxidation of Si(001)-2 * 1 Surface Studied by X-Ray Photoelectron Spectroscopy.

The surface composition of a Si(001)-2 ×1 reconstructed surface after various O2 exposures and the oxidation process in an atomic scale based on the experiments using X-ray photoelectron spectroscopy have been investigated. We have demonstrated that the initial oxidation process is explained by our modified random bonding layer-by-layer mechanism. The suboxide contents (Si1+:Si2+:Si3+) change from 1:0:0, to 2:1:0 to 3:2:1 with increasing O2 exposure. The total suboxide saturates to SiO5/6 which is an intermediate state of the layer-by-layer oxidation, and to a metastable state prior to the nucleation of the two-dimensional SiO2 islands. The ratio of the bridging oxygen atoms to the on-top oxygen atoms is approximately 4:1. The portion of oxygen at the on-top site decreases with increasing O2 exposure. The oxygen atoms preferentially insert into the back bond of the dimer down-atom.

Effects of Wall Charge on Firing Voltage and Statistical Delay Time in Alternating-Current Plasma Display Panels

The effects of wall charge on firing voltage, Vf, and the statistical delay time of discharge, ts, in plasma display panels were investigated. Vf, i.e., the ion-induced secondary electron emission, is independent of both the polarity and amount of wall charge. In contrast, ts, i.e., the exoelectron emission, strongly depends on the wall charge and is smaller for a high positive wall charge, revealing the coexistence of trapped electrons and holes in the surface region. Positive charging of the MgO surface of the cathode side is effective to improve the response of the address discharge.