[en] The performance of a new monochromator using holographically-ruled toroidal blank gratings has been evaluated at the Tantalus-I synchrotron radiation facility. Two gratings, optimized for 80-320 Angstroem and 320-1280 Angstroem respectively, are mounted on a common scan axis and can be exchanged with a flip mechanism. The monochromator is characterized by high flux from 10-150 eV and by its simplicity of operation. Measurements of photon flux, resolution, and polarization are summarized. (orig.)

No abstract available

No abstract available

No abstract available

[en] Investigation of the initial oxidation and interface formation of cubic silicon carbide for the silicon rich β-SiC(100) 3?2 surface reconstruction by high resolution synchrotron radiation-based soft x-ray photoemission spectroscopy is described. The surface is exposed to low doses of molecular oxygen ranging from 1 up to 10 000 L, at surface temperatures from 25 to 500 deg C. Significant formation of SiO₂ is found for the surface at room temperature, with the rate of oxidation increasing with temperature. Valence band data and Si 2p core level spectra show that even at low exposures, significant oxidation is taking place, with a surface reactivity to oxygen much larger than for silicon surfaces. The oxidation products, which are grown at very low temperatures (≤ 500 ^oC) include SiO₂ as a dominant feature but also substoichiometric oxides Si⁺¹, Si⁺², Si⁺³, and significant amounts of mixed oxide products involving C atoms (Si-O-C)

[en] As a spectroscope technique, x-ray absorption near-edge structure (XANES) of core-levels using synchrotron radiation is a wide-spread use for the determination of the molecular composition of solid surfaces. A common detection method measures the yield of secondary electrons, which is proportional to the x-ray absorption coefficient for sufficiently high photon energy. In the experiments reported here, the authors show how the secondary electrons emitted as a result of photoabsorption can be used to generate a magnified image of the sample surface, with fundamental spatial limits determined by the deBroglie wavelength of the emitted electrons. Contrast in the secondary electron spatial distribution contains both typographical and chemical information about the sample surface. The use of tunable synchrotron radiation enables separation of these contributions to the microscopic image, and to spatially resolve surface chemical composition

[en] The performance of a monochromator using holographic-ruled toroidal gratings has been evaluated at the Tantalus-I Synchrotron Radiation Center. The initial design criteria are given, and the flux in the 10-150 eV photon energy range is compared with other UV monochromators. Measurements of photon flux, resolution and polarization are reported. (orig.)

[en] Microscopy and x-ray emission analysis have been performed on Y--Ba--Cu--O superconductors as a function of temperature using a scanning electron microscope equipped with a low-temperature stage. The samples exhibit a superconducting phase transition above liquid nitrogen temperature as determined by resistivity measurements and a demonstrated Meissner effect. Strong contrast changes in the micrographs due to the superconducting phase transition are found, which have been used to identify normal and superconducting regions of the sample. These samples are found to consist of particles with superconducting shells surrounding a nonsuperconducting core

[en] Experimental surface core-level shifts (SCLSs) aid in understanding the roles of altered electronic and screening properties at reconstructed semiconductor surfaces. Because of unresolved theoretical issues, the assignment of SCLSs has often remained controversial even though the surface geometry has been completely determined with traditional probes. Angular- and energy-dependent x-ray photoelectron diffraction (XPD) of each chemically resolved surface core-level electron can be used to discriminate the structure around each chemically shifted species. However, this technique requires tunability, high energy resolution to separate the SCLSs from the bulk core-levels, and high photon flux in order to gather large amounts of data in a reasonable time. Using the newly commissioned spectromicroscopy beamline 7.0 at the Advanced Light Source, the authors have acquired chemically-resolved XPD data for Si(111) 7x7 for several photon energies, and by examination of forward-focusing peaks they can draw tentative conclusions about the atomic origins of each core-level shifted peak

No abstract available