Since early 1970s, when Stern, Lytle and Sayers proposed the analytical method of X-ray absorption spectra, XAFS has been developing year by year both in theories and experimental techniques. Especially the advent of synchrotron radiation in the same years widened the applicability of XAFS to develop new techniques, such as surface XAFS, dispersive XAFS and imaging XAFS, etc. The third generation SR has further improved the XAFS method toward higher spatial, temporal and energy resolutions. It has also opened new routes related to XAFS, such as X-ray fluorescence spectroscopy (XFS), X-ray Raman scattering (XRS) and anomalous X-ray scattering (AXS). History of XAFS from 1970s to the present is briefly reviewed and the prospect in the future is also addressed.
Application of X-ray Absorption Spectroscopy (XAS) to observation of various reactions is reviewed. XAS is a unique tool for studying the local structure around a selected element at atomic scale. XAS can be applied to materials such as crystals, amorphous systems, and liquids, which are situated in various conditions (in gas, at high temperature, with an applied stress,…). Thus XAS is one of the most powerful techniques to investigate the structure change of materials during reactions and understand the mechanism. In this paper, some of typical examples-redox of catalyst, corrosion of steel, heterogeneous reduction of oxides-are shown and their key points are discussed.
Soft X-ray absorption spectroscopy is a broadly used method to investigate the chemical and electronic states of matter. One of the active areas of modern research in soft X-ray analysis is to improve the versatility of the sample environment for in-situ and operando analyses. In the present article, the basics of in-situ and operando analyses using soft X-rays will be introduced with recent topics obtained at SPring-8.
Near-edge X-ray absorption fine structure (NEXAFS) measurements are performed at the beamlines BL 10 and 12 of Saga Light Source (SAGA-LS). NEXAFS spectra are available using the total fluorescence yield (TFY) mode and the conventional total electron yield (TEY) mode at the beamline BL12. The fluorescence yield is obtained by a newly-constructed compact detecter using microchannel plates (MCPs). The simultaneous measurements of the NEXAFS spectra by TFY and TEY modes can reveal the information of the surface and bulk of the sample. In addition, the compact vessel for the transfer of the sample into the equipment without exposure to the atmosphere is available. To preserve the highly clean surface of the sample, the vessel with a battery-driven ion pump is also developed.
Scanning transmission x-ray microscopy (STXM) is a unique measurement technique to perform nanoscale x-ray spectroscopy. In this review, we briefly introduce soft x-ray spectroscopy and microscopy technique, and also describe recent results on magnetic imaging and nanoscale x-ray circular dichroism spectroscopy on magnetic materials using STXM.
The national standards of pressure and vacuum in Japan have been developed, maintained and provided at the National Metrology Institute of Japan (NMIJ). The standards consist of several instruments such as mercury column manometer, pressure balances, static expansion system, and orifice method (continuous expansion method), etc. to cover a wide pressure range from 10−9 Pa to 109 Pa. These standards are disseminated domestically to the users through the calibration chain. The Japanese traceability chain is maintained by NMIJ, accredited calibration laboratories and the accreditation body so as to guarantee the reliability of the pressure and vacuum measurements for users. In this article, how the vacuum standards are developed from the pressure standard is explained then how they are maintained and disseminated are described.
We investigate flaked particles instantaneously generated in mass-production plasma etching equipment. Particles flaking off from films deposited on the ground electrode are detected by using laser light scattering system. Not only the number of particles but also the size of them obviously increases when micro-arc discharge occurs around a wafer and floating potential (inner wall potential) changes instantaneously. The results of this study provide evidence that electric field stress acts as impulsive force due to rapidly changing floating potential, causing dramatically breaking of deposited film and many large particles.