We introduce our laser excited ultrahigh resolution photoemission spectrometer constructed at ISSP. Using a newly developed laser system and an analyzer, we have achieved an energy resolution of 360 μeV that is the highest one in the world. This system has many advantages, high intensity, bulk sensitivity, etc. No differences were observed in the photoemission spectra of Nb samples with and without surface treatment. Many advantages of laser and its high-energy resolution and bulk sensitivity demonstrate the potential of photoemission spectroscopy.
The continuous miniaturization and increasing complexity of the materials used in modern technology requires to have access to chemical composition, electronic structure, magnetization, and fluctuations in these properties at sub-micron and nanometer scales. X-ray photoemission electron microscopy (XPEEM) can provide this information. The recent years have seen a strong increase in XPEEM activities worldwide. This paper reviews the present situation and future developments of XPEEM in combination with synchrotron radiation. In particular, the role of energy filtering, aberration correction, and temporal resolution is discussed.
We have developed a laser-based photoemission microspectrometer which achieved an energy resolution of < 30 meV and a lateral resolution of 0.3 μm. The light source was fs-coherent radiation at a wavelength of 140 nm (8.9 eV). The images based on the intensity of the Shockley-surface-state feature clearly showed that many crystalline grains with (111) surfaces were formed on a polycrystalline copper plate. The high-energy-resolution spectroscopy allows detailed insights on the nm-scale morphology. Another feature of the spectrometer is the measurement of unoccupied states by employing time-resolved two-photon photoemission. Surface images based on the unoccupied image-potential state were successfully measured. We have applied the spectrometer to copper phthalocyanine films grown on a polycrystalline copper substrate. The results demonstrate that a large inhomegeneity exists in the interface electronic structure.
Recently, we have realized hard X-ray photoemission spectroscopy (HX-PES) using high-brilliance synchrotron radiation at SPring-8. High energy (6 and 8 keV) photon excitation enables us to probe photoelectrons with larger escape depth compared to conventional PES. This allows us to conduct a study of intrinsic electronic structure of bulk and embedded interface of materials. A specially designed apparatus including X-ray optics achieves both high energy resolution and high throughput. We report the characteristics and performance of HX-PES, and also the application to study of the electronic structure of new functional materials and strongly correlated electron materials.
By measuring the very low energy photoelectron spectra of Cu single crystal surfaces with a high resolution, we have observed the energy loss structure due to image charge interaction. The structure appears as a spike at zero-kinetic-energy in the Cu(001) spectra. We have proposed that the requirement for appearing the energy loss structure is the absence of unoccupied states at the vacuum level of the Γ‾ point to which zero kinetic energy electrons can return. This result demonstrates that the very low energy photoelectron spectroscopy is a useful tool in analyzing the electron dynamics just outside of the solid surface.
The direct visualization of atomic arrangements is essential for understanding the nature of materials. The rotation of forward focusing peaks in photoelectron intensity angular distribution (PIAD) patterns excited by circularly-polarized light with the left and right helicities are found to be the same as the parallax in stereo-view. Moreover, this method is element selective since the photoelectrons from different core levels are used as a probe. Taking advantage of this phenomenon of PIAD circular dichroism, the three-dimensional atomic arrangement image of crystals and thin films were realized.
We have developed a scanning tunneling microscope (STM) combined with a synchrotron-radiation light source (SR-STM) aiming at elemental analysis in a spatial resolution of STM. Using SR-STM atomically resolved STM images under the irradiation and also X-ray adsorption spectra clearly showing an adsorption edge of a substrate were successfully obtained by detecting photo-emitted electrons with the STM tip. In order to focus the probing area of the photo-induced current, a glass-coated metal tip sharpened with focused ion beam was used as a probe. The present situation and prospects of the instrument are discussed in this review.
Studies on the formation of ordered structures by oscillatory electrodeposition can be divided into two groups; one is treating with the formation of layered structures and the other the formation of dendrites. In part I, we surveyed recent studies on the former group. Here we review on the latter group. The formation of dendrites is reported in various fields such as vacuum deposition and crystallization under super-cooling or super-saturation conditions, as well as the electrodeposition, and explained either in terms of diffusion-limited-aggregation (DLA) or Mullins-Sekerka (MS) instability mechanisms. Recently, we have found that oscillatory electrodeposition of tin (Sn) under current-controlled conditions produces dendrites with a highly ordered latticework structure lying vertical to the electrode surface. This result cannot be explained by the DLA or MS-instability model alone. A combination with another proper mechanism, i.e., an autocatalytic passivation mechanism, has to be taken into account. The generality of the model has been confirmed in the systems of zinc (Zn) and lead (Pb) electrodeposition. The mechanism is quite unique and indicates high potential of producing ordered micro- or nano-structures that can never be produced by other methods.
It was found that the key points of time reduction of bobsleigh were to reduce friction resistance between the runner and ice, and to improve the start technique, from the results of bobsleigh's dynamic analysis. Then, the authors designed and manufactured a new bobsleigh runner based on elastic-plastic contact analysis, which realized minimum contact area between the runner and ice within the shape that prevents ploughing term in friction force. The developed bobsleigh runner based on the analysis was named as “Nagano Special”. Additionally, the authors suggested a new start technique called “Keri-Nori”, which was quite different from the conventional start technique of the Japanese bobsleigh team, and verified its benefit. By using the newly developed bobsleigh runner “Nagano Special” and the new start technique “Keri-Nori”, the Japanese bobsleigh team took the 4th place among the world 44 teams in the international official tryout held on February 1998 just before Nagano Olympic Games.