Tetsuro Fukui

Film Thickness Dependence of Ferroelectric Properties of (111)-Oriented Epitaxial Bi(Mg1/2Ti1/2)O3 Films

The origin of the ferroelectricity of Bi(Mg1/2Ti1/2)O3 films was investigated. Epitaxial Bi(Mg1/2Ti1/2)O3 films with film thicknesses of 50 to 800 nm were grown on (111)cSrRuO3/(111)SrTiO3 substrates by pulsed laser deposition. A Bi(Mg1/2Ti1/2)O3 film was not strongly clamped from the substrate and identified to have rhombohedral symmetry with a = 0.398 nm and α= 89.8°, which was independent of film thickness within 100 to 800 nm. The relative dielectric constant, remanent polarization, and coercive field of the Bi(Mg1/2Ti1/2)O3 films at room temperature were almost constant at about 250, 60 µC/cm2, and 240 kV/cm, respectively, for film thicknesses above 200 nm. These data suggest that Bi(Mg1/2Ti1/2)O3 films are ferroelectric.

Relaxor Characteristics of BaTiO3-Bi(Mg1/2Ti1/2)O3 Ceramics

Relaxor characteristics of (1-x)BaTiO3-xBi(Mg1/2Ti1/2)O3 (x=0.1–0.7) ceramics were investigated. Microstructural observation showed second phases and no domain structure for the sample with x=0.6. Deviation from the Curie-Weiss behavior was found in temperature dependence of the inverse permittivity for all the samples. The stronger dielectric dispersion was found for x=0.6 and 0.7 and they were described by the Vogel-Fulcher relationship. The temperature dependence of the remanent polarization and coercive field indicated the freezing temperature was 100~150°C for x=0.6. The strong dielectric dispersion of x=0.6 is believed to be induced by the structural disorder due to the second phases.

Microstructure and Piezoelectric Properties of BaTiO3-Bi(Mg1/2Ti1/2)O3-BiFeO3 Ceramics

Barium titanate (BaTiO3, BT)-bismuth magnesium titanate (Bi (Mg1/2Ti1/2)O3, BMT)-bismuth ferrite (BiFeO3, BF) solid solution ceramics were prepared using a conventional solidstate synthesis, and their piezoelectric properties and microstructure were investigated. Strain electric field curves of the 0.3BT-0.1BMT-0.6BF ceramics with a single perovskite phase were ferroelectric butterfly-like curves. A strain maximum / electric field maximum (Smax/Emax) was 330 pm/V. Transmission electron microscopy revealed ferroelectric-like domain structure in the 0.3BT-0.1BMT-0.6BF ceramics.

Growth of (111) one-axis-oriented bi(Mg1/2Ti1/2) O3films on (100)Si substrates

Films of a high-pressure perovskite phase, Bi(Mg1/2Ti1/2)O3, were prepared on (111)c-oriented SuRuO3-coated (111)Pt/TiO2/SiO2/(100)Si substrates. The perovskite Bi(Mg1/2Ti1/2)O3 films had a (111) one-axis orientation, because their constituent grains were epitaxially grown on (111)c-oriented perovskite SrRuO3 ones. The remanent polarization and piezoelectric constant measured at an applied electric field of 600 kV/cm were about 30 µC/cm2 and 40 pm/V, respectively. A remarkable phase transition was not observed from room temperature to 350 °C in a (111) one-axis-oriented Bi(Mg1/2Ti1/2)O3 film, suggesting that the Curie temperature of this film is above 350 °C.

10/sup 5/ times biasing current improvement in an electron wave interference device with vertical superlattices

Summary form only given. The authors have fabricated a novel WBT (washboard transistor) with an (AlAs)/sub 1/4/ (GaAs)/sub 3/4/ vertical superlattice. The vertical superlattice (FLS) has a 10-nm-order periodicity perpendicular to the growth direction. The FLS improves the WBTs biasing current by about 10/sup 5/ times compared to the previous WBT with a 500-nm grating gate. The modulation-doped AlGaAs/GaAs heterojunction structure with FLSs is grown on [001]-oriented semi-insulating GaAs substrate with a misorientation angle of 1.0 degrees toward the [110] direction. The electron concentration is about 10/sup 3/ larger than that of the previous WBT, resulting from periodicity reduction from 500 to 16.2 nm. >

New Write-once Optical Media Using Azulenium Dye

New write-once optical media comprising the azulenium dye film are reported. Azulenium dyes having strong absorbance in the near infrared range are synthesized and studied about their optical and thermal properties. The dye film made by a spin-coating process, has a sufficient absorbance and reflectance at a wave length of 830nm. The new media, comprising the dye film have high recording sensitivity and a sharp threshold in recording characteristics.