Soft X-ray beamline BL1N2 at Aichi Synchrotron Radiation Center and its industrial use.

BL1N2 is a soft X-ray XAFS (X-ray absorption fine structure) beamline that is well suited for industrial use. User service started in 2015. The beamline is a grazing optical system with a pre-mirror, an inlet slit, two mirrors for three gratings, an outlet slit and a post-mirror. Light of 150 eV to 2000 eV is available, and K-edge measurements of elements from B to Si are covered. The O K-edge is most often measured; transition metals such as Ni and Cu at their L-edges and lanthanoids at their M-edges are also often measured. Here, basic information about BL1N2, the effect of ageing by synchrotron radiation to remove mirror contamination, and a compatible sample handling system and transfer vessels to allow a one-stop service at three soft X-ray beamlines at AichiSR are described.

Surface EXAFS via differential electron yield.

Surface-sensitive analysis via extended X-ray absorption fine-structure (EXAFS) spectroscopy is demonstrated using a thickness-defined SiO2 (12.4 nm)/Si sample. The proposed method exploits the differential electron yield (DEY) method wherein Auger electrons escaping from a sample surface are detected by an electron analyzer. The DEY method removes local intensity changes in the EXAFS spectra caused by photoelectrons crossing the Auger peak during X-ray energy sweeps, enabling EXAFS analysis through Fourier transformation of wide-energy-range spectral oscillations. The Si K-edge DEY X-ray absorption near-edge structure (XANES) spectrum appears to comprise high amounts of SiO2 and low Si content, suggesting an analysis depth, as expressed using the inelastic mean free path of electrons in general electron spectroscopy, of approximately 4.2 nm. The first nearest neighbor (Si-O) distance derived from the Fourier transform of the Si K-edge DEY-EXAFS oscillation is 1.63 Å. This value is within the reported values of bulk SiO2, showing that DEY can be used to detect a surface layer of 12.4 nm thickness with an analysis depth of approximately 4.2 nm and enable `surface EXAFS' analysis using Fourier transformation.

Effective nitrogen doping into TiO2 (N-TiO2) for visible light response photocatalysis.

The thickness-controlled TiO2 thin films are fabricated by the pulsed laser deposition (PLD) method. These samples function as photocatalysts under UV light irradiation and the reaction rate depends on the TiO2 thickness, i.e., with an increase of thickness, it increases to the maximum, followed by decreasing to be constant. Such variation of the reaction rate is fundamentally explained by the competitive production and annihilation processes of photogenerated electrons and holes in TiO2 films, and the optimum TiO2 thickness is estimated to be ca. 10nm. We also tried to dope nitrogen into the effective depth region (ca. 10nm) of TiO2 by an ion implantation technique. The nitrogen doped TiO2 enhanced photocatalytic activity under visible-light irradiation. XANES and XPS analyses indicated two types of chemical state of nitrogen, one photo-catalytically active N substituting the O sites and the other inactive NOx (1⩽x⩽2) species. In the valence band XPS spectrum of the high active sample, the additional electronic states were observed just above the valence band edge of a TiO2. The electronic state would be originated from the substituting nitrogen and be responsible for the band gap narrowing, i.e., visible light response of TiO2 photocatalysts.