Core-level photoelectron diffraction provides element-specific atomic structure information. Forward focusing peaks (FFPs) indicate the directions of atoms surrounding a photoelectron emitter atom. When a core level is excited by circularly polarized light, angular momentum of light is transferred to an emitted photoelectron, which can be confirmed by the parallax shift measurement of FFP direction. Here I report the new observation and quantitative analysis of the angular momentum transfer from light to Auger electrons, and compare them with the photoelectron cases. Angularmomentum-polarized Cu LMM Auger electrons at the L absorption threshold, where the excited core electron is trapped at the conduction band, were detected. By setting an analyzer at the corresponding position in the FFP direction, the Auger electron with a specific angular momentum can be selectively detected. In the case of magnetic materials, circular dichroism in the X-ray absorption intensity was observed together with angular momentum transfer (parallax shift) effect.
Recent results on grazing-incidence small-angle scattering have been introduced with emphasis on the use of tender X-rays. Merit of using longer wavelength to understand depth dependence of nanostructures in thin films are presented, along with some drawbacks in using long wavelength. Applications on semiconductor nanodots and micro-phase separated block copolymer thin films are shown. Use of resonant scattering in the tender X-ray region gives opportunity for contrast matching GISAXS experiments, which may reduce complicated situation of dynamical effect upon analysis.
Angle-resolved photoemission spectroscopy (ARPES) is a powerful experimental tool for revealing the electronic band structure of solids. Excellent characteristics of synchrotron radiation light enable us to achieve specialized ARPES measurements. In order to perform such experiments, we have constructed a new beamline BL-2 MUSASHI (Multiple Undulator beamline for Spectroscopic Analysis of Surface and Hetero-Interface) at Photon Factory, KEK. As examples of the specialized ARPES measurements by utilizing the advantage of this beamline, we introduce recent ARPES results on ( 1 ) three-dimensional electronic structures with changing the photon energy, ( 2 ) bulk electronic structures using high energy soft x rays, and ( 3 ) orbital-selective electronic structures by polarization dependent ARPES measurements.
All the stainless steels have specific “native passive films” formed on the surfaces. Previously, we have elucidated that the passive film on SUS304, typical 18Cr stainless steel, consists of a Cr(IV) oxyhydroxide (-O-Cr-OH-) network structure and Cr2O3deposited near the film/SUS interface: This dense passive film prevents bulk Fe-components from dissolving into the surface-adsorbed water. In this paper, we give explanations for the passive film on the SUS440C (18Cr-1C) surface, comparing with the case of SUS304 (18Cr-8Ni). As a result, due to the carbon components in SUS440C, fragmentation of Cr oxyhydroxide is promoted in the passive film. Therefore, the corrosion resistance of SUS440C becomes less than that of SUS304. Additionally, we report an interesting structural change of the SUS304 passive film observed by using in-situ total reflection X-ray absorption spectroscopy.
For the Cu2ZnSnS4 (CZTS) photovoltaic (PV) cells with a common structure of the window-layer (WL)/buffer-layer (BL)/absorbing-layer (AL), the band offset and band slope were measured by hard x-ray photoelectron spectroscopy. In view of the efficient transport of photo-excited free-electrons from CZTS-ALs to WLs via CdS-BLs, the conversion efficiency of the PV cells would be significantly affected by the band offset at BLs/ALs interface and the band slope in BLs. For the CZTS PV cells with a relatively high conversion efficiency of 9.4%, the conduction band offset at CdS-BLs/CZTS-ALs interface was estimated to be 0.1±0.1 eV with a cliff-type, and the band slope in CdS-BLs was estimated to be 0.5±0.1 eV (downward slope to WLs) in the case of ZnO:Ga-WL. Absence of CB barrier at BLs/ALs interface and larger downward band slope in BLs to WLs are essential for higher conversion efficiency of the CZTS PV cells.
Storage ring based synchrotron radiation light source generates photons of high flux and high brightness simultaneously. Many storage ring light sources are under user operation in the world now. Recently developed fourth generation light sources have higher brightness by about one hundred times than those of ordinary third generation light sources. In this paper, I show the basics of synchrotron radiation, beam physics and finally the lattice design of fourth generation light sources.