Osamu Yamazaki

Rectangular-apertured micro-Fresnel lens arrays fabricated by electron-beam lithography.

Rectangular-apertured micro-Fresnel lens arrays are proposed. These lens arrays have been fabricated by an electron-beam writing system specially developed for the fabrication of microoptical devices. It is experimentally demonstrated that the lens arrays showed uniform focusing characteristics, and that each lens exhibited a diffraction-limited focusing characteristic with efficiency of 74%.

Study of the density of the d-state and structure transformation of Pt fine particles dispersed on carbon electrodes by in situ X-ray absorption spectroscopy

Abstract The structure and density of the d-state of Pt fine particles on a carbon electrode were investigated in H 2 SO 4 and NaOH solutions by in situ X-ray absorption fine structure spectroscopy. The applied potential was changed between −0.2 V and 1.3 V vs. Ag/AgCl for 0.26 M H 2 SO 4 solution. The total density of the unoccupied d-state h T increased according to the potential and was always larger in the negative sweep than in the positive sweep. Around 0.0 V vs. Ag/AgCl in H 2 SO 4 , h T agreed in both sweep directions, that is, a kind of hysteresis was observed in this voltammogram. The coordination number and the disorder factor were determined for the first Pt-Pt shell. The disorder of the structure of the particles (decreasing N and increasing σ) increased in the course of the positive sweep and disappeared at the hydrogen region after reversal of the sweep. The relation of the structural change to the hysteresis of the d-density is discussed with respect to cyclic voltammograms of Pt.

Computer‐controlled electron‐beam writing system for thin film micro‐optics

A computer‐controlled electron‐beam writing system has been developed. The system has various functions for fabricating thin film micro‐optical devices. The ability of 0.1‐μm patterning, smooth circular and elliptic scanning of an electron beam, and excellent blazing characteristics have been demonstrated. The system has been confirmed to be an efficient means for fabricating micro‐optical devices.

Thickness Dependence of Superconductivity in As-Sputtered Er-Ba-Cu-O Thin Films

Thin films of Er-Ba-Cu-O system with various thickness have been prepared on R-plane of sapphire by rf-magnetron sputtering. As-sputtered films thicker than 0.15 µm showed superconductivity. As the thickness of the films increased, the transition width decreased and the critical current density increased. As-sputtered film with 1-µm thickness exhibited superconducting transition at onset temperature of 91 K and the zero-ρ state was observed below 80 K.

Hydrogen absorption and Li inclusion in a Pd cathode in LiOH solution

Abstract The amount of electrochemically absorbed hydrogen and lithium in a Pd cathode during electrolysis was measured quantitatively in LiOH solution. The electrode potential was also measured by the current interruption method. Inclusion of Li in Pd was found even at the potential of −0.22 V vs. RHE. This potential is far more positive than the reported UPD potential. Since Li was detected up to a depth of 200 nm, this phenomenon is not a simple UPD. The deposition of Li onto Pd and the formation of PdLi alloy are likely to occur at a much more positive potential than expected. The [ H ] [ Pd ] ratio decreased gradually after 50 h electrolysis at a current density greater than 5 mA cm−2.

Properties of High Tc Superconducting Quantum Interference Device Microscope with High µ-Metal Needle

A new type of superconducting interference device (SQUID) microscope was designed and fabricated. A direct-coupled SQUID magnetometer with a high µ-metal needle was used and the substrate was machined to create a dimple for the needle at the center of the pick-up loop. One end of the needle penetrated through the superconducting pick-up loop in a vacuum; the needle was fixed in the vacuum window with the other end at room temperature in the outside atmosphere. As a demonstration, a laser printed output was scanned by the microscope. Line bars with a line width of 100 µm and a spacing between lines of 200 µm were clearly imaged.

Windowless High-Tc Superconducting Quantum Interference Device Microscope

A high-Tc superconducting quantum interference device (SQUID) microscope with a sample chamber isolated by a shutter gate was designed and constructed for imaging samples at both room temperature and 77 K. According to our scheme, the separation of the sample from the SQUID can be less than several micrometers, in principle. We have successfully imaged a trapped flux in a YBa2Cu3O7-y thin-film ring at 77 K.

Preparation of (Pb, La)TiO3?PbTiO3 Thin Films with Superlattice Structure

(Pb, La)TiO3–PbTiO3 thin films with superlattice structure have been successfully grown on sapphire substrates. Each layer of epitaxial perovskite structure was alternately deposited by computer-controlled multi-target co-sputtering system. The minimum modulation wavelength was about 100 A and interdiffusion significantly occurred when thickness of periodic layer was less than 100 A.

Electrochromic Effects of Li‐W‐O Films under Ultraviolet Light Exposure

Electrochromic effects of WO/sub 3/ films have been extensively studied. In these electrochromic films, the injection of both I-group ions and electrons form a tungsten bronze (color center) structure (M/sub x/WO/sub 3/, x=0-1, M is H, Li, or Na). It is known that an intervalence electron transfer between W/sup +6/ and W/sup +5/ causes blue coloration in these films. Previously, the authors reported a new fabrication method and the properties of double-layered Li-W-O films. The WO/sub 3/ films exhibit photochromic effects as well as electrochromic effects. In this paper they describe the electrochromic effects of the double-layered Li-W-O films under UV light.

Novel spectroelectrochemical cell for in-situ XAFS spectroscopy on gas generating electrodes

The recent advance of the in-situ spectroscopic methods in electrochemistry has greatly promoted the understanding of the electrode/ electrolyte interface. Among them x-ray absorption spectroscopies have contributed to the elucidation of the structure and electronic state of the electrode surface [l-41. Yet it has been difficult to apply these spectroscopic methods to some electrodes during electrolysis because of gas evolution on the surface. This difficulty appears not only in x-ray methods but also in any spectroscopy and scanning tunneling microscopy. The in-situ characterization of such electrodes has been restricted mainly to conventional electrochemical methods. In order to extend the potential window where spectroscopy can be applied, developing a spectroelectrochemical cell in the gas evolving region is indispensable. Spectra are disturbed by bubbles of generating gas sticking to the surface. This is because the transmission coefficient of the photon in gas phase is generally much larger than that in the solution and the state of the bubble on the surface is mobile. Gas generation at the surface, growth into bubbles and desorption from the surface may occur at any time. Lu and Stern have reported on a powder sample that the error of extended x-ray absorption fine structure (EXAFS) oscillation, x(k), reaches up to 10% when 400 mesh was used for selecting FeSi, powder [5]. This implies that the EXAFS spectra with good signal/noise ratio are possible if the size of the gas bubble is restricted. Therefore, it is necessary to remove the bubbles from the system before they grow. In this article we propose