Akira Nishiwaki

Electric and thermoelectric properties of electrodeposited bismuth telluride (Bi2Te3) films

We investigated the relationships among the deposition potential, the electric properties, and the thermoelectric properties of Bi2Te3 films electrodeposited from a solution containing 1.00mM TeO2 and 0.86mM Bi-EDTA complex. From the results of the Hall-effect measurements, the films formed at >−0.27V vs Ag∕AgCl were Te-rich n-Bi2Te3, and the carrier concentration increased with more negative deposition potential. The films formed at <−0.35V were Bi-rich p-Bi2Te3, and the carrier concentration showed a constant value. A depth profile showed that all the electrodeposited films were composed of two layers, and that an n-type layer containing a large excess of Te existed near the substrate surface. From the Seebeck coefficient measurements, the electrical type of all the films was n type, and the maximum Seebeck coefficient (−70±10μVK−1) was observed for the film deposited at −0.20V. The electrical type obtained by the Seebeck coefficient measurements was completely different from the electrical type determi...

Applications of TiO2 film for environmental purification deposited by controlled electron beam-excited plasma

Abstract Taking advantage of the remarkable features of controlled electron beam-excited plasma (EBEP), the composition and the thickness of TiO 2 film could be directly controlled by the EBEP accelerating voltage V A and discharge current I D , respectively. Experiments were conducted on the dissolving effect on NO x (NO, NO 2 ) gas using glass beads coated with a TiO 2 film deposited by EBEP. With a bead sample size of 20 g and an NO gas flow rate of 100 ml/min, the NO dissolvable amount was approximately 10 −4 mol/m 2 for 120 min. Using a glass plate, glass beads and zeolites coated with TiO 2 film, the experiments succeeded in dissolving water-soluble ink and in obtaining a hydrophilic effect.

Epitaxial growth and characterization of stoichiometric LiNbO3 films prepared by the sol-gel method

After stoichiometric LiNbO3 thick films were deposited on z-cut LiNbO3 substrates using the sol-gel method from a precursor solution containing various polyvinyl alcohol (PVA) concentrations, their characteristics were investigated. The film thickness increased linearly with the increase in PVA and precursor concentrations. The orientation relationships between films and substrates were determined by x-ray diffraction, Raman spectroscopy, and transmission electron microscopy, and the results showed that (006) oriented LiNbO3 epitaxial layers with parallel epitaxial relationships could be grown on a z-cut LiNbO3 substrate. The refractive indexes of the films were n0=2.28±0.02 and ne=2.19±0.02 at a wavelength of 632.8nm, and their transmission loss was 0.50±0.04dB∕cm.

Preparation and Characterization of Ti Doped LiNbO3 Films Grown by the Sol-gel Method

Crack-free and very smooth Ti-doped LiNbO3 (LN) films were obtained on z-cut LN substrates by the sol-gel method using solutions containing the LN precursor and a large amount of polyvinyl alcohol (PVA). Titanium (Ti) ions were added to the precursor solutions to prepare optical waveguide films on LN wafers using our sol-gel method. The characteristics of the films containing various Ti concentrations were investigated. The refractive indexes of the films prepared from the sol containing 1.5 mol % Ti ions were no=2.307 and ne=2.257. The average transmission loss for the films was about 0.5 dB/cm in the TM mode at a wavelength of 632.8 nm.

Dimensional Measurement at a Point on the Diffusing Surface by Using Speckle Pattern Interferometry

A collimated light beam from a He-Ne Laser, is transformed into two beams by using a concave lens and a beam-splitter cube, in a Twyman-Green-type interferometer. When a diffusing surface is placed at the focal point of one of the two beams, a diverging spherical wave front containing large-sized speckle patterns is scattered. If a smooth surface reference mirror is placed in the vicinity of the focal point of the other beam, the reflected beams have essentially the same shaped wave front. The two beams can be combined to form concentric interference fringes, which are fairly regular. By observing the concentric fringes flowing out or sinking in, it is shown that the normal component of the displacement of the diffused surface can be measured with an accuracy of a fraction of a half wavelength.