Research and development of a new material is usually conducted by the following processes. First, physical, chemical, electrical and magnetic properties of newly synthesized materials are measured. In the next step, we analyze the structure of the materials, which includes electrical structure, state of electrons around atoms, crystal structure, and atomic coordination. Results of those measurements and analysis are fed back to the synthetic process in order to obtain materials with more valuable properties. By repetition of synthesis and analysis, we aim to develope new materials suitable for our purpose. Recent drastic progress of computer technology enables us to predict the material properties of the structure by computer simulations. From this point of view, knowledge of material structure is of great importance in materials research.

X-rays interact with electrons around atoms in materials. The interaction generates many phenomena such as transparent, diffraction, scattering, absorption, fluorescence and photoelectron. Analyses of such phenomena gives us information about electron state, binding energy of electrons, symmetry of structure and atomic coordination of materials. Thus, we can obtain structural information of materials using X-rays as probes.
X-rays have both characters of particle and wave. X-rays as a particle can strike out electrons captured around atoms inside of materials, which is called photoelectron. We can determine binding energy of the electron by measuring the kinetic energy of the photoelectrons. Further, by analyzing energy distribution, we can reveal the state of the electron or chemical bonding in materials. On the other hand, X-rays as a wave occurs diffraction. We can determine atomic coordination (crystal structure) of crystalline materials by measuring the direction and intensity of the diffracted X-rays.

Synchrotron X-rays have many advantages compared to conventional X-rays.

1. Low divergence
2. High energy resolution
3. High intensity and brilliance
4. Tunability of X-ray energy
5. Controllability of polarization
6. Pulsed X-ray

X-rays with low divergence and high-energy resolution enables us to investigate the material structure more precisely. Further, investigation of nano-size materials requires X-rays with high intensity and brilliance. If X-ray energy can be varied according to the purpose of experiments, we can expand the range of binding energy measured by photoelectron electron experiments and atoms used for fluorescence analysis. Controllability of polarization is convenient for investigating the magnetic character of materials. Moreover, pulsation of synchrotron radiation can be applied for time-resolved experiments.
There are many synchrotron radiation facilities in the world and SPring-8 is a 3rd generation synchrotron radiation ring with the highest acceleration energy. At SPring-8, structures of semi-conductors, metals, inorganic or organic materials, proteins, etc. are investigated by applying the advanced features of synchrotron X-rays. At present, synchrotron radiation is an indispensable tool for research of new materials.

National Institute for Materials Science has constructed a beamline at SPring-8 (BL15XU), in order to conduct advanced analysis of synthesized materials. At present, analysis of electron structure, band structure, chemical bonding state, atomic coordination and crystal structure of materials are conducted by means of hard X-ray photoelectron spectroscopy, high-resolution powder diffraction and thin-film/surface diffraction. For these purposes, BL15XU has prepared the following 3 apparatuses.

1. High resolution powder diffractometer
2. Hard X-ray photoelectron spectrometer
3. 8-axis thin film diffractometer

Details of these apparatuses are given in each web page. BL15XU can provide X-rays with an energy range from 2.2 to 36 keV. The energy range from 6 to 20 keV X-rays are most frequently used for experiments. In future, we plan to analyze one sample by both photoelectron spectroscopy and X-ray diffraction in order to understand electron and crystal structure of materials at once. Further, we plan to develope structure analysis by applying polarization or pulsation of synchrotron X-rays.