Kazutami Kawamura

Properties of hydrophone with porous piezoelectric ceramics

We constructed a hydrophone using porous piezoelectric ceramics and conducted a detailed investigation into hydrophone sensitivity under higher pressure and its acceleration sensitivity as vibrational noise. At a pressure of 7.85 MPa, the hydrophone sensitivity of the porous piezoelectric ceramic hydrophone was some 20 dB higher than that of the piesoelectric ceramic hydrophones. The difference in acceleration sensitivity between the porous piezoelectric ceramics and the piezoelectric ceramics was extremely minor. The hydrophone sensitivity is sufficiently high to allow us to consider vibrational noise as negligible.

High‐corrosion‐resistant magneto‐optical recording media using TbFeCoTi films

The effects of adding Ti to TbFe and TbFeCo films with and without protective layers were studied. The addition of Ti improved the corrosion resistance of the films. The transmittance of TbFeCo films was reduced by a factor of 10 by the substitution of 5% Ti for Fe, and by a factor of 100 by the substitution of 10% Ti for Fe. Pit formations in TbFeCo during aging in a corrosive condition and immersion in a NaCl solution were almost completely eliminated by the substitution of 5% Ti for Fe. The Kerr rotation angle (θk) decreased slightly in TbFeCo by the substitution of 10% Ti for Fe, while improving the corrosion resistance.

High luminance white EL devices using SrS:Ce,Eu,K films deposited in a H2 atmosphere

Abstract White EL devices were fabricated using SrS:Ce, Eu, K phosphor films deposited in a reducing atmosphere of H 2 . The highest luminance of 1700 cd/m 2 was obtained under 1 kHz sinusoidal voltage drive. This value is 2.3 times larger than that of the devices without atmosphere of H 2 . Compared to phosphor films prepared without an atmosphere of H 2 gas, the residual oxygen concentration in the films had decreased by one half, additionally, the X-ray diffraction pattern showed a preferential (200) orientation.

New, deep UV resist (LMR) for lift‐off technique

A new, deep UV resist, LMR (low molecular weight resist) has been developed. LMR is a quinone–diazide ester of a novolak resin whose molecular weight is about 1000. It has strong absorption in the deep UV region (12 μm−1 at 250 nm). LMR is negative working upon irradiation with deep UV light and forms an overhung structure with a single development step. The sensitivity of LMR is 30 mJ/cm2 and 0.3 μm wide spaces are clearly resolved. By use of LMR, a simple and reliable lift‐off process is realized. Submicron wide metal patterns having a thickness twice that of the resist can be formed by this process.

Improvements in corrosion resistance of Tb‐Fe thin films

Electrochemical corrosion of Tb‐Fe films was studied by immersion in a NaCl solution. The corrosion resistance was improved by adding Al, Cr, Hf, Mo, and/or Ti to Tb‐Fe. The improvement mechanism, which was studied by transmittance change measuring, microscopic observation, and electron probe microanalysis, is the concentration of the additive metals and formation of passive states by the metals.

New trilevel and bilevel resist systems using silyl ethers of novolak and low molecular weight resist

A new intermediate layer material, silyl ether of novolak (Si–novolak), and a new Si containing resist, silyl ether of a naphthoquinone diazide ester of novolak, Si–LMR (low molecular weight resist), have been developed for trilevel and bilevel resist systems, respectively. Si–novolak has high O2‐reactive ion etching (RIE) resistivity and high solubility in nonpolar solvents, such as xylene and chlorobenzene, which cause no damage to the film of novolak. When novolak and Si–novolak are employed as the bottom and intermediate layer materials, respectively, both layers can be formed by successive coatings without baking the bottom layer. Si–novolak is easily hardened by deep UV light. Therefore, a trilevel resist can be formed by one deep UV blanket exposure and one baking step, besides coating steps. The triresist system, LMR/Si–novolak/novolak, provides 0.5 μm resist patterns with steep profiles and good line control over topography. Si–LMR is a negative deep UV resist and its sensitivity is 100 mJ/cm2. T...

Properties of porous PZT ceramics for hydorophone applications

Porous PZT ceramics were produced by lamination of green sheet mixed PZT ceramics and spherical carbon, and firing. The relationship between its porosity and piezoelectric properties or hydrophone sensitivity were investigated. At the porosity 50%, the piezoelectric voltage coefficient (gh) of the porous ceramics increased by one order or more when compared to the value at the porosity 0%, and the hydrophone sensitivity was improved more than 10 dB.

High Tc Superconductivity of Y-Ba-Cu-O Ceramics

The superconductivity and structure was studied in Y-Ba-Cu-O ceramics. BaCO3, Y2O3, CuO were mixed at a composition of YBa2Cu3O6.5, calcined at 900°C for 5 h, and sintered under various conditions. The critical temperature was 90 K for the ceramic sintered at 950°C for 10 h. The structure was analyzed with scanning electron microscope, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy.

MAGNETO-OPTICAL MEMORY MEDIA USING BATION PROTECTIVE FILMS

A new protective and enhancing film for magneto‐optical memory media—BaTiON has been developed. The values of refractive index and extinction coefficient of the film were 2.75 and 0, respectively. Calculations give maximum Kerr rotation angles of 1.4 deg for three‐layer‐type media and more than 10 deg for reflective‐layer‐type media when such a film is used to enhance the rotation. The magneto‐optical memory media using the film showed excellent recording characteristics.

Formation of thick and narrow-spacing metal patterns by lift-off technique using negative photoresists, LMR and LMR-UV

Abstract We already reported a negative resist, LMR, for deep uv (230–280 nm) lithography. It gives overhung profiles by simple development. We have further developed a new developer which enables LMR to be workable with light in a wider spectral range. 2.0 um thick Au patterns having 0.75 um metal-metal spacings are achieved by lift-off technique with this developer. LMR-UV has been developed for uv (350–450 nm) lithography. It is a negative working resist and forms overhung profiles in a similar manner to LMR.