[en] Polycrystalline Fe-8.75at. % Si alloys were investigated at room temperature by various surface spectroscopies, i.e., Auger electron spectroscopy (AES) (including Ar⁺ depth profiling), electron energy loss spectroscopy (EELS), and x-ray induced photoelectron spectroscopy (XPS), during the initial oxidation stages under very low oxygen pressure. Experiments performed include (1) scraping to see if the surface concentration of Si on the alloy is inherently different from that of the bulk, (2) AES, EELS, and XPS monitoring during both initial oxidation of pure Fe and Fe-Si, and Ar⁺ or Xe⁺ etching back to the clean surfaces to determine the relative distribution of Si in the oxide and alloy, and (3) various comparative experiments to identify oxidation states across a thin oxide layer. Fe-6.85at. % Si (110) and (111) single crystal surfaces, and a (110) surface of pure Fe were investigated at room temperature by AES and LEED during the initial oxidation stages under very low oxygen pressures, and by Ar⁺ AES depth profiling the oxidized surfaces back to the clean surface. Experiments performed include (1) determination of the best annealing condition for each crystal to provide the cleanest single plane surface, (2) AES monitoring during both initial oxidation of pure Fe and Fe-Si (110), the close-packed plane of bcc crystals, and Ar⁺ etching back to the clean surfaces to determine the relative distribution of Si in the oxide and alloy, and (3) repetition on Fe-Si (111) to see the effects of different crystallographic orientations on the initial oxidation behavior. 126 refs., 36 figs., 6 tabs

[en] Metamaterials (MMs), which are not existing in nature, but artificially-engineered materials for controlling electromagnetic wave. MMs have attracted more and more research attentions, since they have shown greatly novel properties such as left-handed behavior, negative refractive index, classical analog of electromagnetically-induced transparency, and extraordinary transmission. Among MMs, MM perfect absorbers (MMPAs), which are useful to enhance the efficiency in capturing solar energy and applied to various application areas, have been rapidly developed. In general, the structure of MMPAs is very simple, which consist of three layers: patterned conductor layer, which is used for minimizing the reflection by impedance matching, dielectric layer and continuous conductor layer for blocking the transmission. In addition, the unit-cell size of general MM absorbers is only 1/3−1/5 of the working wavelength of incident electromagnetic wave. Nevertheless, the properties of general MMPAs are in problems of the absorption only at specific frequency, the narrow absorption band, the polarization sensitivity and so on. In this review paper, the introduction of recent researches in the field of MMPAs operating in different frequency ranges is presented. Moreover, the researches on the improved electromagnetic properties are discussed, which comprise multi-band, broadband, tunable, polarization-insensitive, and wide-incident-angle MMPAs. The perspectives and the future works for the further investigations and the various real applications of MMPAs are also presented.

[en] Published in summary form only

[en] We studied the correlation between the microstructures and the optical diffraction properties in femtosecond-laser-induced gratings of an amorphous Co₂MnSi (a-Co₂MnSi) film. The a-Co₂MnSi thin film was deposited on a glass substrate by using magnetron sputtering, and the crystallization of the a-Co₂MnSi film was performed using two-beam interference of near-infrared femtosecond laser pulses. For the femtosecond-laser-interference crystallization using two 120-μJ laser beams, the diffraction intensity slowly increased with the laser shot count until it reached a maximum intensity around 25900 laser shots; then, the diffraction intensity gradually decreased. From the cross-sectional and the plan-view transmission-electron-microscopy images of the laser-crystallized Co₂MnSi regions, the crystallization reached deeper into the sample film under an optimized fluence condition. Meanwhile, a lower fluence beam resulted in a partially crystallized film, and a higher fluence beam made a partially damaged film. The femtosecond-laser-induced gratings consisted of alternating semicrystalline-Co₂MnSi and polycrystalline-Co₂MnSi bands with a period of about 2-μm.

[en] We analyzed the surface of an extruded Al-Mg-Si model chamber for SPring-8 by SEM and AES from the points of view of outgassing and desorption loads. Three typical surfaces were subject to the analysis: the ordinary surfaces before and after the cleaning process to understand their characteristics and extraordinary corrosion specks to figure out the nature and origin of unexpected specks. The top 30-60 A of the ordinary oxide overlayer was found to be Mg oxide-rich regardless of cleaning and understood to be due to the segregation or evaporation of Mg during extrusion. On the other hand, a lack of Mg oxide was observed on the corrosion specks all the way and resulted only in a porous and extremely thick (∼690 A) Al oxide. This result indicates an important role of the top Mg oxide-rich layer in the retardation of further oxidation of Al. These specks are interpreted to grow by chemical and atmospheric attack after the top oxide was removed at cleaning under the conditions of shake-up during the high-temperature procedure.(author)

[en] The report describes major features of the accumulation ring designed for the large-scale synchrotron orbit radiation facilities which are being designed by the Joint Study Team for Synchrotron Orbit Radiation established under the Institute of Physical and Chemical Research and the Japan Atomic Energy Research Institute. The vacuum in the accumulation ring should be lnTorr or below in the electron-accumulated state to ensure a beam lifetime of about 20 hours. To achieve this vacuum, an Al alloy (A6063T6) extruded in an Ar+0₂ atmosphere is adopted as material for the vacuum chambers (straight chamber, bending chamber). Non-evaporation type getter (NEG) pumps and distributed ion pumps (DIP) are provided for the straight and bending chambers, respectively. Three types of pumps (centralized NEG pump, sputter ion pump, titanium sublimation pump) are provided for the crotch absorbers, which are to be directly irradiated with synchrotron radiations. The report briefly outlines the beam lifetime in the accumulation ring, some features of the vaccum chambers, thermal output and degassing rate associated with synchrotron radiation, and characteristics of the various pumps. (N.K.)

[en] The electronic structures, the magnetic moments and the optical conductivity spectra of the Co_1-xAl_x (x=0.5, 0.4375, and 0.375) alloys were calculated using the tight-binding linearized-muffin-tin-orbital method. The supercell method was employed to calculate the properties of the alloys with the off-stoichiometric concentrations. The calculated magnetic moments were in reasonable agreement with the experimental results. The inclusion of corrections for both the real and the imaginary parts of the self-energy markedly improved the agreement between the experimental and calculated the optical conductivity spectra

[en] The structural dependences of the galvanomagnetic properties of Co-Al and Fe-Al alloy films were investigated in this study. Ordered and disordered alloy films with thickness of 150 nm were prepared by using the flash evaporation technique on the heated and cooled substrates, respectively. The temperature dependence of resistance was measured in the range of 2 ∼ 300 K range with and without a magnetic field of 0.5 T. The influence of the order-disorder structural transition on the temperature dependence of the resistance is discussed in connection with the results for the magnetic properties and is analyzed in the framework of the partial localization of the electronic states and variable-range hopping conductivity

[en] By employing an orthogonal linear-polarization combination, (+45 .deg. ,-45 .deg. ), we prepared a surface relief grating (SRG) and a birefringence grating (BG) on an azo polymer film. Atomic force microscopy (AFM) showed that the SRG height gradually increased, and the height was 56.5 nm at an input fluence of 63 J/cm². All the diffraction orders from the gratings were measured simultaneously, and the BG characteristics were analyzed from the s and the p components of the first-order diffraction beam and the measured SRG height. The BG showed an abrupt increase in the beginning of writing, but decreased shortly later, and became smaller than the SRG at a few minutes after writing. The phase shift between the two gratings was determined to be π, which is crucial for determining the SRG formation mechanism.

[en] In this research, we investigated the microstructures, the photoluminescence (PL) and the nonlinear optical properties of semiconductor nanocomposites consisting of ZnO nanorods and CdS nanodots. The ZnO nanorods and the CdS nanodot-adsorbed ZnO nanorods were grown in an aqueous solution of Zn(NO₃)₂ and hexamethyltetramine (HMT) by using chemical bath deposition. The room-temperature PL spectra under 325-nm continuous wave excitation showed an UV emission band with a peak at 3.25 eV and a band width of 160 meV, while the PL spectra at a low temperature of 10 K exhibited multiple bands with enhanced PL intensities. These results are thought to be related to the near-band-edge emission that originates from exciton transitions. From femtosecond Z-scan measurements at a wavelength of 800 nm, the ZnO nanorods exhibit nonlinear absorption due to three-photon absorption, and the CdS nanodot adsorbed ZnO nanorods show the saturable absorption due to the exciton bleaching effect of the CdS nanodots.