Keishi Nishio

Preparation and properties of electrochromic iridium oxide thin film by sol-gel process

Abstract We established a method for preparation of iridium oxide thin film by the sol-gel dip-coating process where iridium chloride was used as a starting material. The coating solution was prepared by reacting iridium chloride, ethanol and acetic acid. Iridium oxide coating was formed at 2.0 cm/min withdrawing rate. The coating films heat treated at 300°C did not contain impurities. Iridium oxide crystallized at temperatures above 450°C. Both crystalline and amorphous iridium oxide thin films showed electrochromism. The change in transmittance of the crystalline Ir2O3 film is larger than that of the amorphous Ir2O3 under the same experimental conditions. The transmittance of the crystalline thin film (film thickness 200 nm, measured at 400 nm) decreased 13.0% on application of 3 V for 1 s.

Preparation and electrical properties of ITO thin films by dip-coating process

Indium tin oxide (ITO) thin films were prepared on quartz glass substrates by a dip-coating process. The starting solution was prepared by mixing indium chloride dissolved in acetylacetone and tin chloride dissolved in ethanol. The ITO thin films containing 0 ∼ 20 mol% SnO2 were successfully prepared by heat-treatment at above 400 °C. Chemical stability of sol were investigated by using a FTIR spectrometer. The electrical resistivity of the thin films decreased with increasing heat-treatment temperature, that is carrier concentration increased, and mobility decreased with increasing SnO2 content. The ITO thin films containing 12 mol% SnO2 showed the minimum resistivity of ρ=1.2 × 10−3 (Ω cm). It also showed high carrier concentration of N=1.2 × 1020(cm−3) and mobility μH=7.0(cm2 V−1 s−1).

Preparation of highly oriented thin film exhibiting transparent conduction by the sol-gel process

Highly oriented thin films exhibiting transparent conduction aluminium-doped ZnO (AZO), were prepared by a spin-coating method. The effects of the solvents on the preparation and electrical properties of the thin films were examined. The thin films were formed on quartz glass substrates by spin-coating into a selected solution and calcining at 700 °C for 5 h. The thin films had a resistivity of ρ (Ω cm)=1.5 after heat treatment in an air atmosphere, and 1.5 × 10−3 Ω cm in a reducing atmosphere, and a transmission of about 85% in the visible light region. The differences in the high orientation and the conductivities were attributed to a chelate formation in the aluminium-doped ZnO due to the solvent effect.

Photosensitivity in phosphate glass doped with Ag+ upon exposure to near-ultraviolet femtosecond laser pulses

We report on a photosensitivity in soda-alumino-phosphate glass doped with silver ions Ag+ upon exposure to near-ultraviolet femtosecond laser pulses. The photosensitivity, i.e., formation of color centers such as Ag0 and Ag2+ in the glass is found to be associated with intensity-dependent nonlinear optical process induced by extremely high irradiance up to ∼TW/cm2 of the femtosecond pulses. We demonstrate a bright orange fluorescence from the induced color centers inside the glass, that should be applicable to a functional optical device.

Investigation of glass formation and color properties in the P2O5–TeO2–ZnO system

Abstract The compositional dependence of glass-forming tendency and thermal properties was investigated for the P2O5–TeO2–ZnO system with the aid of an automatic sample preparation system including a batch-preparing apparatus and a multi-sample casting machine. The samples exhibited a variety of colors, such as transparent, yellow, wine red and brown depending on composition. Analyses with scanning electron microscopy and X-ray photoelectron spectroscopy revealed that the reddish coloration results from a colloidal suspension of nanometer-sized elemental Te particles.

Transport properties of LaTiO3/SrTiO3 heterostructures

Resistivity measurements show that SrTiO3/LaTiO3/SrTiO3 heterostructures remain metallic even for single unit cell LaTiO3 layers. Hall resistances of all heterostructures are nonlinear functions of the applied field. The Hall data is analyzed in terms of a two-layer model, indicating that a low-mobility layer exists at the LaTiO3/SrTiO3 interface, while carriers with mobilities approaching 10 000 cm2/V s are present deep in the SrTiO3 substrate.

Structural Analysis and Properties of Organic-Inorganic Hybrid Ionic Conductor Prepared by Sol-Gel Process

Organic-inorganic hybrid lithium ion conductors were prepared by the sol-gel process. The hybrid ion conductor will be used as the electrolyte for Li based high-energy density batteries. The hybrid ion conductor was prepared from a mixture of tetramethyl orthosilicate (TMOS), polyethylene glycol 200 (PEG200), lithium perchlorate (LiClO4) and water. A wet gel was prepared at room temperature. The gels dried at 80°C under vacuum did not contain water. The dried hybrid ion conductor gel had homogeneity and high transparency. Ionic conductivity of the hybrid sample was measured by the complex impedance method and it increased with increasing PEG200 content. The dried hybrid gel that contained no LiClO4 did not show ion conduction. Conductivity on the order of 10−5 S·cm−1 at room temperature was obtained. Structural characterization was done by Fourier Transform Infrared Spectra (FTIR) and NMR measurement of 13C and 1H, and the thermal stability and glass transition properties were studied by DSC. Glass transition temperature decreased with increasing PEG200 content and increased with increasing [Li]/[O] ratio (the oxygen considered is from the polyethylene glycol). Existence of the Si–O–(C2H4O)n–bond and the C–OH bond in the framework of the organic and inorganic phases was confirmed. TMOS and PEG200 were hydrolyzed and condensed. The organic and inorganic phases were chemically bonded and the microstructure of the hybrid matrix was shaped as comb. The comb shape leads to high ionic conduction.

Propagation of surface plasmon polariton in nanometre-sized metal-clad optical waveguides.

Using a local anodic‐oxidation method with a probe tip of a scanning near‐field optical microscope (SNOM) as the electrode, we have fabricated an oxide core with subwavelength dimensions on metal. The propagation of the surface plasmon polariton (SPP), which is excited at the interface between the oxide core and the metal clad, has been investigated using the same SNOM. Altering the wavelength of input light from 532 nm to 830 nm, the propagation length of the SPP extends from 2 µm to 6 µm. We carried out a simulation of the SPP propagation, and obtained a similar wavelength dependence.

Preparation and Properties of Highly Oriented Sr0.3Ba0.7Nb2O6 Thin Films by a Sol-Gel Process

We succeeded in the preparation of epitaxial or highly oriented strontium-barium niobate (Sr0.3Ba0.7Nb2O6) thin film by a sol-gel process. A homogeneous coating solution was prepared with Sr and Ba acetates and Nb(OEt)5 as raw materials, and acetic acid and diethylene glycol monomethyl ether as solvents. Sr0.3Ba0.7Nb2O6 film sintered at 900°C on MgO(1 0 0) was oriented with c-axis perpendicular to the substrate surface. Sr0.3Ba0.7Nb2O6 film sintered at 700°C on SrTiO3(1 0 0) was an epitaxial and oriented with c-axis in parallel to the substrate surface. Transmittance of Sr0.3Ba0.7Nb2O6 film (film thickness: 144 nm) was more than 60% at the range from 400 to 800 nm. Refractive index was 2.33 at 633 nm. Dielectric constant and dielectric loss of the Sr0.3Ba0.7Nb2O6 thin films prepared on polycrystal Pt substrates were 600 and 0.06 at room temperature and 1 kHz, respectively. The curie temperature (Tc) of polycrystalline Sr0.3Ba0.7Nb2O6 thin films was about 200°C. At room temperature and 50 kHz, remanent polarization (Pr) and coercive field (Ec) of the polycrystalline thin films were 1.79 μC/cm2 and 2.69 kV/cm, respectively.

Synthesis and Properties of Highly Conductive Thin Films as Buffer Layer from Sol-Gel Process

We prepared epitaxial growth SrRuO3 thin film on LaAlO3 (001) (LAO) single crystal substrate and highly oriented BaTiO3 ferroelectric thin film on the epitaxial SrRuO3 thin film. A homogeneous precursor solution for preparing SrRuO3 thin film was prepared with Sr(O—i—C3H7)2 and Ru(NO)(NO3)3 as starting materials, and 2-methoxy ethanol as solvents. The as-coated thin films were heat treated at temperatures from 723 to 1273 K for 1 h in air. SrRuO3 grew epitaxially on LAO(001) substrate, which were confirmed by XRD theta-2theta method and XRD pole figure analysis. The crystallographic relationship of the film and substrate was SrRuO3(001) parallel to LAO(001) and SrRuO3[110] parallel to LAO[100]. A homogeneous precursor solution for preparing BaTiO3 thin film was prepared with Ti[O—n—(CH2)3CH3]4 and Ba(OCOCH3)2 as starting materials, and acetic acid, 2-methoxy ethanol. SrRuO3 coated LAO substrates were coated by spin-coating method with the coating solution. The as-coated thin films were heat treated at temperatures from 973 to 1173 K in air. It was confirmed that the thin films were growing orientated for c-axis by measurement of XRD theta-2theta method.