Recent situation of industrial implementation of Cat-CVD technology in Japan

Efforts of industrial application of Cat-CVD technology are surveyed. Recent movement of industrial implementation is also reviewed by showing examples in Japanese industry. Cat-CVD technology is originally developed as a new tool for fabricating semiconductor devices, however, recently, use of the technology is attempted in various fields such as chemical, mechanical and bio-technical engineering. It is shown that Cat-CVD has high feasibility as a fundamental technology of modern industries.     

Self-routing planar network for guided-wave optical switching systems

An N*N self-routing planar network suitable for fabricating optical space switches on lithium niobate substrate is presented. The network has O(N/sup 2/) cross points, good modularity and expandability. It also has no waveguide crossovers and no differential attenuation between any of the input and output pairs. A self-routing control can be applied to this network, which is indispensable for ATM switching systems.<>     

Valence Band Structure of ZnO (1010) Surface by Cluster Calculation

Discrete variational (DV) Xα cluster method has been employed in calculating electronic structures of ZnO. Electronic structures of the bulk and the non-polar surface model clusters are calculated with inclusion of electrostatic potentials in the bulk and near the surface, and the electronic origins of experimental spectra and chemical bonds at the surface are examined in detail. The valence band structure constructed by Zn-3d and O-2p bands is much influenced by electrostatic potentials in ZnO. It is found that the reduction of an electrostatic potential near the surface gives rise to the difference of the valence band structures between in the bulk and at the surface. The calculated density of states at the non-polar surface of ZnO, where the Zn-3d and O-2p bands are more widely separated than in the bulk, is in good agreement with the experimental UPS. In addition, a Zn-O bond at the surface is found to show stronger covalency than that in the bulk, as a result of the change of the valence band structure due to the effect of the electrostatic potential.     

SOLUBILITY IN ORGANIC DILUENTS AND EXTRACTION BEHAVIOR OF CALIX[4]ARENE CARBOXYLATES WITH DIFFERENT ALKYL CHAINS

ABSTRACT

Two types of alkylcalix[4]arene carboxylates with different alkyl chains, together with three types with the same alkyl chains were synthesized to investigate their solubility in four different organic diluents. The solubility was found to be enhanced by using the calixarene compounds with longer alkyl chains and by using mixtures of compounds with different alkyl chains. The order of solubility in the different organic diluents was found to be:

chloroform > toluene ? EXXSOL D80 ≈ hexane.

The stoichiometry of the copper complex with the compounds having the same alkyl chains was also determined and the maximum loading capacity of copper with each extractant was estimated.     

Comparison of platinum with IrO2–Ta2O5 system for the stannous ion consumption in methane sulfonic acid baths with and without catechol

The stannous ion consumption in methane sulfonic acid (MSA) baths with and without catechol was quantitatively evaluated using platinum and IrO₂–Ta₂O₅/Ti anodes. The stannous ion is consumed at the same rate with both anodes, accompanied by the generation of tin sludge on the anode surfaces in the bath without catechol, while these undesirable phenomena are significantly suppressed in the bath containing catechol. Spectroscopic measurements indicate that stannous ion and catechol form a complex at the mole ratio of 1:2, thus preventing the oxidation of stannous ions. This complexation effect is independent of the anode material at low current density, but depends on the anode material at high current density. The stannous ion consumption at high current density is sufficiently inhibited only with the IrO₂–Ta₂O₅/Ti anode due to the low oxygen evolution potential. Voltammetric measurements also suggest that the continuous oxidation of stannous ion in the catechol-containing bath is simultaneous with oxygen evolution.     

Application of finite fourier transformation for the solution of the diffusion equation

Application of the finite Fourier transformation is discussed for the solution of the diffusion equation in one dimension, two dimensional x-y and triangular geometries. It can be shown that the equation by the Nodal Green's function method in Cartesian coordinate can be derived as a special case of the finite Fourier transformation method.     

Effect of microstructures on dielectric breakdown strength of sintered reaction-bonded silicon nitride ceramics

Silicon nitride (Si₃N₄) was prepared from silicon by a sintered reaction-bonded silicon nitride method using yttria and magnesia as sintering additives. Post-sintering (PS) of nitrided compacts was carried out at 1850°C under a nitrogen pressure of 1 MPa. Effect of PS time on microstructure and dielectric breakdown strength (DBS) of the prepared Si₃N₄ ceramics was evaluated. The DBS was measured using specimens with four different thicknesses (0.30, 0.20, 0.10, and 0.05 mm) in order to examine the thickness dependence. The porosity of the sintered Si₃N₄ decreased by prolonging the PS time, and the full density could be achieved at the PS time of over 6 h. After full densification, rod-like β-Si₃N₄ grains grew up, and their maximum grain size increased from 45.1 to 154.7 μm by prolonging the PS time from 6 to 48 h. The DBS of the thick Si₃N₄ substrates (0.30 mm) showed little variation from 35.4 to 47.0 kV/mm, regardless of the PS time. On the other hand, that of the thin ones (0.05 mm) dramatically decreased from 99.5 to 9.8 kV/mm with increased the PS time from 6 to 48 h. Because the DBS sharply decreased at the thin substrate sintered for longer time in which some large-elongated grains might span the substrate thickness-wise throughout, it was inferred that the interface between β-Si₃N₄ grains and grain boundary phase/intergranular glassy films might be a path of the dielectric breakdown.