Takayuki Watanabe

The ferroelectricity of Bi4Ti3O12 (BIT), (Bi3.2La0.8)Ti3O12 (BLT), Bi4(Ti2.97V0.03)O12 (BTV), and (Bi3.2La0.8)(Ti2.97V0.03)O12 (BLTV) films prepared at 600 °C by metalorganic chemical vapor deposition was compared. For the BIT, BLT, BTV films deposited on (111)Pt/TiO2/SiO2/Si substrates, the ferroelectricity was not obtained even though the films consisted of a single phase. On the other hand, the BLTV films exhibited clear ferroelectricity. Furthermore, the degree of squareness of the hysteresi

The dynamic responses of a spherical bubble in an acoustic standing wave field are studied numerically. The equations of motion in the translational and the radial directions are solved simultaneously. It is shown that a bubble which is larger than the resonance size moves to a node of the pressure field and its radial oscillations become small. A sufficiently small bubble is shown to move to an antinode and radially oscillates under the maximum pressure amplitude. It is found using Poincaré map

Nonlinear carrier relaxation/recombination dynamics and the resultant stimulated terahertz (THz) photon emission with excitation of surface plasmon polaritons (SPPs) in photoexcited monolayer graphene has been experimentally studied using an optical pump/THz probe and an optical probe measurement. We observed the spatial distribution of the THz probe pulse intensities under linear polarization of optical pump and THz probe pulses. It was clearly observed that an intense THz probe pulse was detec

a- and b-axis-oriented epitaxial Bi4Ti3O12 films were prepared on (101)TiO2 (rutile) substrates at 630 °C by metalorganic chemical vapor deposition and their perfect epitaxial growths were confirmed by several x-ray diffraction measurements. As the bottom electrode, (101)-oriented conductive materials with the same rutile-type structure as the TiO2, RuO2, and IrO2, were epitaxially grown on (101)TiO2, (012)Al2O3, and (110)Al2O3 substrates. Finally, a- and b-axis-oriented Bi4Ti3O12-based material

This article describes the current progress in thin bismuth layer-structured ferroelectric films (BLSFs) including SrBi2Ta2O9 and (Bi,La)4Ti3O12, particularly those developed in the last ten years. BLSF thin films can be applied to ferroelectric random access memories because of their durable fatigue-free properties and lead-free composition. We will briefly introduce epitaxial thin films grown on a variety of substrates. Because of the difficulty in growing single crystals of sufficient size to

The site engineering approach based on site-selective substitutions was utilized to improve the ferroelectric properties in Bi4Ti3O12 thin film. Thin films of (Bi4−xNdx)(Ti3−yVy)O12 with both A- and B-sites substitutions were deposited on (111)Pt/Ti/SiO2/Si substrates at 600 °C by metalorganic chemical vapor deposition. Although the films substituted for the A site by Nd, (Bi4−xNdx)Ti3O12, showed no significant improvement in ferroelectricity, additional substitution for the B site by V contribu

This paper reviews recent advances in the design and performance of our original InP- and GaAs-based plasmonic high-electron-mobility transistors (HEMTs) for ultrahighly-sensitive terahertz (THz) sensing and imaging. First, the fundamental theory of plasmonic THz detection is briefly described. Second, single-gate HEMTs with parasitic antennae are introduced as a basic core device structure, and their detection characteristics and sub-THz imaging potentialities are investigated. Third, dual-grat