An introduction to the use of synchrotron radiation and an overview of the main facilities throughout the world are presented. The fundamentals, such as its generation and advantages, are described briefly. “Photon Factory”, the synchrotron radiation facility in Tsukuba, is described as one example.
In this paper, a brief introduction of bulk and surface Extended X-ray Absorption Fine Structure (EXAFS) and a review of the recent developments in the field of Surface EXAFS are presented. Results for S K-edge SEXAFS of c (2×2) S/Ni (110) obtained recently at Photon Factory are discussed. Finally, several new techniques related to EXAFS are introduced.
In this review, the current theoretical methods for the interpretation of XANES are discussed, and some applications of XANES to surface science are illustrated. For theoretical problems, we discuss the cluster size to be included in the calculations, polarization dependence, multiple scatterings and many-body effects. For the applications to surface science, two examples are given. One is the measurement of the surface XANES under nonvacuum conditions, the other is the bond-length determination from intramolecular multiple scattering.
Surface and adsorbate structural studies by Synchrotron Radiation (SR) in the hν=10-200eV range are reviewed. It is stressed that the continuum of clean, polarized intense radiation from synchrotron has made it possible to do measurements that are not possible with conventional light sources available in the laboratory. In this sense, SR adds a new dimension to photoelectron spectroscopy.
In electron-and photon-stimulated desorption (ESD/PSD), beams of energetic electrons or photons incident on a surface containing terminal bulk atoms or an adsorbed monolayer of molecules or atoms will cause electronic excitations at the surface. In the present paper we review mechanisms of ESD/PSD, as well as examples of the benefits of electron- and photon-stimulated desorption to study molecules at surfaces. Moreover, ESD ion angular distribution (ESDIAD) and angular resolved PSD (ARPSD) are also surveyed for characterizing the geometry of srufacemolecules. A schematic bonding model of adsorbed H2O molecules interacting with electronegative adsorbate (oxygen) and electropositive adsorbate (sodium) and the experimental results of ESDIAD are discussed. The ESD/PSD of polyatomic molecules are also included. The provable resulting explosion of ESD/PSD containing desorption of neutrals and negative ions is discussed.
Principles of crystal structure analysis are briefly stated from the standpoint that an amplitude of the diffracted rays represents a Fourier coefficient of the electron density distribution in the specimen. The descriptions of an anisotropic distribution of 3d electrons around the transition metals in complex compounds and minerals are presented as the most prominent examples of the precise analyses using conventional X-ray sources. Effects of the anomalous scattering are discussed and the way to distinguish the atoms of neighbouring atomic numbers is explained with the reason for its being effectively utilized at the Photon Factory. Some processes, especially for handling the data from the synchrotron radiation source, are mentioned.
A conventional X-ray diffraction can be utilized for the determination of the structure of interfaces. Since X-rays do not interact strongly with the material they are probing, there are some difficulties with X-ray diffraction in two-dimensional physical systems. In recent years, two approaches have been developed. One is to deposit layers on powdered adsorbents while the other is to use grazing incidence scattering. The method is contrasted to electron diffraction to show why it offers unique advantages for certain classes of problems such as the phase transitions of physisorbed layers, the crystallography of clean reconstructed surfaces and the structures of solid-solid, solid-liquid and liquid-gas interfaces. The application of the method, as well as the principle and the instrumentation is described.
This paper shows the present status of experimental apparatus and the results from synchrotron radiation (SR) X-ray topography at Photon Factory in KEK. The real time observation by using X-ray TV can be achieved at SR X-ray topography, so the main purpose of these experiments is to get information on dynamic behavior ; for example melting and growth processes, phase transitions and etc. The typical experiments for such subjects are described. Recently, monochromatic X-ray topography was tested by using wiggler beam line, and it was confirmed that the real time observation could be also achieved and that the sample heating from the radiation of X-ray beam was negligibly small at monochromatic X-ray topography.
The use of synchrotron radiation in the gas phase is quite useful for understanding photochemical primary processes in vacuum UV region because of the continuous character of the light intensity against the wavelength in the whole region. In the present paper photochemical primary processes associated with the use of synchrotron radiation are reviewed. In addition, we present some experimental results on the photochemical reactions of molecular clusters. The advantages of the use of a supersonic molecular beam combined with synctrotron radiation are demonstrated.
Photon with the energy of 1eV has the infrared wave length. However, it corresponds to the thermal energy of about 11600°K. Therefore, photo-chemistry can induce chemical reactions with very high activation energy. Moreover, the radicals or ions of a single sort are induced as a result of irradiation of light source with a single wave length. Therefore, the induced chemical reaction is specified even with impure materials. The measurement for the identification of a radicals or ions concerned in the reaction is also another merit of the photo-reactions. In this paper, photo-assisted chemical reactions are explained and the molecular layer epitaxy, which made the crystal growth accurate in the order of single atomic dimensions, is explained, followed by the effect of ultra-violet light irradiations. These methods are also valuable to clarify surface adsorbed phenomena and also its reactions. Some experimental results are explained.
Fundamental aspects and present status of synchrotron radiation lithography (SRL) are described. The resolution is limited mainly by Fresnel diffraction and the penetration range of photoelectrons within the resist layer. Wavelength dependences of these factors indicate that the optimum resolution of 0.10.2μm can be obtained at the wavelength of 610Å. Throughput attainable with SRL in a step and repeat regime is evaluated on the basis of exposure field size which affords overlay accuracy of 1/4 of the minimum linewidth. The result shows that reasonable throughput in sub half micrometer pattern replication is possible by use of resists with moderate sensitivity in the order of 100mJ/cm2 or less if X-ray flux is as high as that produced by a normal storage ring with energy of 800MeV and current of 500mA. Discussions on requirements for compact storage ring, enlargement of exposure field, temperature rise in masks due to high flux irradiation, and factors affecting the overlay accuracy, together with some experimental results are also presented.
Applications of synchrotron radiations to metals research are reviewed regarding structure and surface analysis. Synchrotron radiations have great advantages in structure analysis especially by X-ray topography, EXAFS and time-resolution experiments. Dynamic in situ observations by X-ray topography have provided interesting information on the progress of recrystallization and grain boundary migration in metals. Observations of substructures and magnetic domains by the present authors are also included. EXAFS gives the atomic configurations in metallic glasses and that of alloying elements of crystalline metals. Laser annealing of silicon and crystallization of metallic glasses can be followed by the time-resolution experiments. Interesting results obtained recently by the techniques for surface analysis such as surface EXAFS, XRF, UPS, XPS and AES are presented, and the authors' study on high sensitive analysis by AES is described. Synchrotron radiations are expected to expand their applications as sophisticated and effective means for internal and surface analysis in the field of metals and materials science.
Recent studies on the surface structure of several supported bimetallic catalysts by use of EXAFS spectroscopy are reviewed. EXAFS spectroscopy is a very powerful technique for investigating the structure of the supported bimetallic catalysts because it provides direct information on the metal-metal interactions. It is revealed that there exist various kinds of metal-metal interactions in the bimetallic systems. In RuCu/SiO2, copper atoms are dominantly located at the surface of the bimetallic particle, while, in PdAu/SiO2, the surface composition of the bimetallic particle is equal to the bulk. (That is, the alloy particles are formed.) Other types of metal-metal interactions are also discussed. Our recent EXAFS studies clearly revealed that the direct Rh0-Fe3+ bondings are present in the RhFe/SiO2 catalyst, and that in the RhCo/γ-Al2O3 system the cationic cobalt atoms are again directly bonded with the cationic rhodium atoms. In these systems, it is very important to characterize not only metal-metal but metal-support interactions in order to understand the relation between the surface structure and the catalytic properties.
A brief survey is made of the application of synchrotron radiation to biological studies. Then, as examples, X-ray diffraction studies of early processes of muscle contraction are described, where early processes include Ca2+ release from sarcoplasmic reticulum, structural change of the thin filament and change of distribution of myosin heads.
The activity of the Working Group of Mineralogy at Photon Factory was reported, and the earliest results of the following items were briefly presented : x-ray toaograahy of a cube-shaped diamond, reinvestigation of the lilianite structure, examination of single crystal, diffraction data collection from micro-size specimens using a four-circle diffractometer., the absolute orientation of hemimorphite, cation ordering in the structure of Cu9As4Se13, modulation in α-Al2O3 crystallite formed in the process of dehydration of diaspore, RDF study employing anomalous scattering effect, cation distribution in pentlandite at high temperature, a trial of high temperature high pressure single crystal x-ray study using high temperature diamond anvill cell on SOR beam, superstructure of tetrataenite from the Saint-Severan meteorite, diffuse scattering from β-PbF2, measurement of diffuse streaks scattered by fine segregates of β-MnO2, and others.
An overview is given for spectroscopic studies of organic polymers using synchrotron radiation, such as (1) absorption and reflection spectroscopy, (2) photoelectron spectroscopy, (3) photochemistry and photodesorption, and (4) fluorescence spectroscopy. Following the classification of electronic excitations in organic polymers and some details of sample preparation, examples of the above items are given for both valence and inner-shell excitations. Importance is stressed for new developments such as (1) site-selectivity of inner-shell excitations, (2) feasibility of probing the intramolecular energy-band dispersion relation in a single polymer chain by angle-resolved photoelectron spectroscopy, and (3) possible use of soft X-ray fluorescence for a detailed study of the valence electronic structures.