The use of medium-sized highly brilliant soft X-ray synchrotron radiation (SR) enables analyses with much better spatial, energy and time resolution, resulting in visualizing surface/interface electronic structure in nano regions. In order to improve performances of electronic, magnetic and energy devices, it is required to characterize and control electronic structures. In the world, several SR rings with the emittance of less than 1 nmrad are being constructed, aiming at revolutionary progress of surface/interface sciences using soft X-rays. Although we have constructed the University of Tokyo Outstation at SPring-8 for soft X-ray surface/interface sciences, medium-sized highly brilliant SR ring is strongly required for further development in this field. In this article, nano-region photoelectron spectroscopy for graphene FET and ReRAM, soft X-ray emission spectroscopy for fuel cells and Li ion batteries, and time-resolved photoelectron spectroscopy for photocatalysts are introduced, and future prospects of soft X-ray surface/interface sciences are discussed.
Future plans for synchrotron radiation research are described after a broad overview of progress in Japanese synchrotron radiation science. In particular a recent plan of high brilliance light source, which is proposed to Master Plan 2014 of Science Council of Japan by the Japanese Society for Synchrotron Radiation Research, is reported in detail. Lastly, the perspectives in materials and life sciences using synchrotron radiation will be mentioned.
Since there has been a strong requirement in Japan for a new medium size synchrotron radiation facility that provides high brilliant photons in the soft X-ray region, the SLiT-J project is proposed by 7 national universities in Tohoku area. In addition to the synchrotron radiation characteristics, the manuscript describes a basic concept of designing the storage ring, expected performance of the SLiT-J and future prospects of the project.
Progress of spectroscopic studies in soft-X-ray regime is discussed. From the first utilization of ES (Electron Synchrotron) in University of Tokyo, synchrotron radiation spectroscopy, especially in vacuum ultraviolet and soft-X-ray region plays important rolls for the study of condensed matters. Not only the advanced synchrotron light source but also new detection methods have given us a lot of advantages in investigations especially in surface science. Recent trend in spectroscopy is combination with microscopy and time-resolved measurements. These show us the frontiers in intrinsic nature of matters.
Si-based electronics has reached an ultimate fabrication level (22 nm design rule), which makes further progress hardly achieved. Therefore, 2D atomic layers including graphene have been extensively studied as next-generation device materials to supplement device functions which Si-based electronics cannot serve. Unfortunately, however, there is a gap between material electronic properties and device performances in the researches on 2D atomic layers. We demonstrate soft x-ray operando spectromicroscopies, photoemission electron microscopy (PEEM) and 3D scanning photoelectron microscopy (3D nano-ESCA), in SPring-8 to bridge the gap in graphene research. The complementary use of these operando spectromicroscopies enables us to probe both valence band and conduction bands of graphene channels under operation, resulting in revealing the effects of the interfaces with contact metal and oxide. The significance of the operando spectromicroscopy is now recognized, resulting in the adoption as a major research target in NEDO academic-industrial alliance project.
A novel experimental technique, time-resolved wavelength-dispersive soft X-ray imaging spectroscopy, is proposed in order to achieve real-time and real-space resolved spectroscopy for the observation of irreversible and inhomogeneous surface chemical reactions. By combining the wavelength-dispersed soft X rays, in which the X-ray wavelength (photon energy) changes as a function of position on the sample, with the photoelectron emission microscope, the soft X-ray absorption spectra are separately obtained at different positions on the sample without scanning the X-ray monochromator. Therefore, the real-time resolved measurement of site-selective soft X-ray absorption spectroscopy is realized in one event without repeating the chemical reaction. It is expected that the spatial distribution of different chemical species is traced during the surface chemical reaction, which is essential to understand the reaction mechanism.
Live cell imaging is important to understand the cell function such as membrane dynamics. Scanning probe microscopy (SPM) is used for evaluation of cell surface topography with nano-scale, but in most cases the measurement induced cell damage when probe contact with the cell surface. Scanning Ion Conductance Microscopy (SICM) uses ion current as a feedback signal for nanopipette probe-sample distance control. SICM allows non-contact live cell imaging and high-resolution characterization of dynamic changes of cell surface. Furthermore, SICM can combine with other analytical tool as distance control technique.