Masaru Hayashi

Structural modulation and superconducting properties in Bi2-xPbxSr2CaCu2O8+d and Bi2-yPbySr2YCu2O8+d

Abstract Changes in the structural modulation and the superconducting properties were examined in Bi 2- x Pb x Sr 2 CaCu 2 O 8+ d and Bi 2- y Pb y Sr 2 YCu 2 O 8+ d systems. In both systems, the b -axis decreased and the periodicity of the structur al modulation along the b -axis increased with increasing Pb content, and the structural modulation disappeared in a high Pb concentration region. These changes in structural modulation were explained by the decrease in additional oxygen in the Bi-O layer. Besides this relaxation of the structural modulation, the superconducting transition became sharper, and a slight increase in T c was observed in the Bi 2- x Pb x Sr 2 CaCu 2 O 8+ d system.

Bulk and Wire Type Y–Ba–Cu Oxide Superconductor

We have fabricated the bulk Y–Ba–Cu oxide, various types of wire conductors and coils, and especially studied the critical current density Jc. Large Jcs were obtained at 77K and OT: 725A/cm2 for the non sheath wire, 560A/cm2 for the Ag sheathed wire. However, the Jc(77K) drastically decreased by a factor of hundred in a magnetic field lower than 1T while Jc(4.2K) little changed up to 12T. Based on the magnetic field dependence of Jc, for example, 2T of upper critical field Bc2(77K) and 47 to 80T of Bc2(4.2K) were obtained for the wire conductor.

Determination of Ultratrace Amounts of Metallic and Chloride Ion Impurities in Organic Materials for Microelectronics Devices After a Microwave Digestion Method

A digestion method was developed for the determination of ultratrace concentrations of sodium, potassium, magnesium, calcium and chloride ions. Using ETAAS and ion chromatography, the digestion method was applied successfully to the determination of ultratrace concentrations of these elements in organic materials for microelectronics devices such as photoresists, epoxy resins, and liquid crystals. Very low contamination levels were maintained throughout the procedure. The blank levels were 0.05 ng for sodium, 0.02 ng for potassium, 0.03 ng for magnesium and calcium, and 20 ng for chloride ion. The method is very effective in measuring the impurity distributions of organic materials whilst preventing their contamination from the surrounding environment and from the reagents used in the procedure.

Evaluation of a mirror-polishing technique for fluorocarbon polymer surfaces for reduction of contamination from containers used in ultratrace analysis.

A mirror-polishing technique for fluorocarbon polymer surfaces using high-precision diamond cutting tools was developed. The goal of this technique was the reduction of ultratrace elemental analysis contamination levels of containers fabricated from such mirror-polished materials. Remarkably smooth inner surfaces with degrees of flatness of 0.1 μm peak-to-valley (PTV) for containers fabricated from mirror-polished PTFE materials were obtained, in contrast to degrees of surface flatness of more than 30 μm PTV for commercially available PTFE containers. (Here, PTV denotes the difference between the highest peak and deepest valley in a scanned area of 10 × 10 μm.) Extractable impurity levels for mirror-polished PTFE container surfaces were reduced by more than 1 order of magnitude relative to those of unpolished PTFE containers. The surface conditions of the PTFE containers were observed by atomic force and scanning electron microscopy. The microphotographs so obtained suggest that the degree of surface smoothness of the containers is proportional to their ultratrace metallic contamination levels.

Oxygen Deficiency and Cu Valence States of Superconducting Y-Ba-Cu Oxide

The oxygen deficiency, Cu valence states and superconducting properties were analized on Y0.4Ba0.6CuO3-x. The critical temperature and the normal-state resistivity varied depending on the change of CuIII/CuII ratio and/or the oxygen deficiency caused by the sintering atmospheres.

Determination of ultratrace metallic impurities in fluorocarbon polymers by electrothermal atomic absorption spectrometry after decomposition with a combustion system

A combustion system method for determining ultra-trace impurities in fluorocarbon polymers was developed. 200 mg polytetrafluoroethylene (PTFE) material samples were inserted into a quartz combustion system and decomposed for 30 min in air. Sodium-, potassium-, calcium-, copper-, and iron-concentrations in the raw PTFE materials ranged between 2–96, 1–35, 4–18, <1 and 12–97 ng g−1, respectively, with blank levels of 0.3, 0.2, 0.4, 0.2, and 0.5 ng/analysis, respectively. The impurity profiles of the fluorocarbon polymers indicated that the polymers were contaminated as a result of the polymer processing procedures. The technique reported herein gives low blank concentrations and is a rapid and safe analytical method for fluorocarbon polymers.

Determination of impurities in strontium titanate ceramics by inductively coupled plasma mass spectrometry

The determination of impurities in SrTiO3 by ICPMS was investigated. The sample was decomposed with hydrochloric and hydrofluoric acids in a PTFE pressure vessel. The internal standard method using Au was selected to eliminate an ion count suppression by the Sr and Ti matrix. Impurities at sub μg/ml level in SrTiO3 were determined. The detection limits were in the range of 0.008 to 0.01 μg/g.

Evaluation of Ultratrace Metallic Impurities in Thin Copper Layers, Barrier Metals and Silicon Wafers for Copper Metallization Technology

An analytical method for the determination of ultratrace concentrations of metals in several semiconductor-related materials for copper metallization technology such as thin Cu layers, barrier metals and silicon wafers has been developed. Using this method, the concentration of Cu impurities in Si wafers resulting from diffusion of Cu from Cu metallization layers through barrier layers of TiN, TiSiN, or WSiN was found to be less than 1012 atoms/cm3.

Determination of Surface Impurities on a Gallium Arsenide Wafer by Inductively Coupled Plasma Mass Spectrometry

The surface impurities on a GaAs wafer were determined by inductively coupled plasma mass spectrometry to clarify the diffusion behavior which affected the layer construction. The sample was etched by hydrofluoric acid in a PTFE vessel at room temperature. Depth analysis of the wafer was performed by repeated etching as impurities were thought to exist near the wafer surface. Copper was difficult to dissolve by hydrofluoric acid due to an ionization tendency compared to the hydrogen ion. The method used in this study was demonstrated to be effective for determining surface impurities on a GaAs wafer for an impurity level of 1011 atoms/cm2 and for analyzing depth profiles from the surface.