Papers by Author: Kaori Nishizawa

Abstract: A novel photoresponsive zirconia (ZrO2) precursor solution was prepared using zirconium tetra-n-butoxide, 4-(phenylazo)benzoic acid and ethyleneglycol monomethylether. Two kinds of ZrO2 films were prepared using the photoresponsive ZrO2 precursor solution and by dip-coating while applying an electric field to the substrates: one was the film prepared with ultraviolet (UV) irradiation to the solution and as-deposited films; the other was the film prepared without UV irradiation. It was found that the surface roughness of films was greatly changed by UV irradiation. Furthermore, the photocatalytic activity of the rough film was greater than that of the smooth film.

Abstract: Nanoscale TiO2 is widely used in consumer products like sunscreen and cosmetics. The establishment of damage evaluation test method was attempted to examine the potential neurotoxicity of nanoscale TiO2 to human body skin in vitro model. The emergence amounts of carbon dioxide, which was expected one of the generation products from the skin according to the titania photocatalyst nanoparticles activity under UV / visible light radiation, were identified and measured by the gas analyzer. It was found that it could evaluate the degrees of damage to skin with the photocatalysts activity by using the new evaluation test method considered.

Abstract: A new photochromic ZrO2 precursor solution was prepared using zirconium tetra-n-butoxide, 4-(phenylazo)benzoic acid and ethyleneglycol monomethylether. The density functional theory (DFT) calculation has identified that the structure of the synthesized precursor molecule changed by UV irradiation. The two kinds of thin films were prepared using the photosensitive ZrO2 precursor solution without and with UV irradiation. The surface morphology of thin films changed by UV irradiation. It was found that the surface morphology of thin films is controlled by the difference of precursor structure introduced by UV irradiation.

Abstract: Y0.5Yb0.5MnO3 ferroelectrics/HfO2 stacking layers were successfully constructed on Si(100) substrates through the chemical solution deposition. The degree of c-axis orientation and microstructure of Y0.5Yb0.5MnO3 ferroelectrics was improved by the control of concentration of precursor solutions. Capacitance of Pt/Y0.5Yb0.5MnO3/HfO2/Si structure was almost constant over 104 s on the retention property.

Abstract: To fabricate porous and thick alumina films, we prepared an aqueous alumina hydroxide sol containing trehalose. The alumina films were deposited by dip-coating technique on glass substrates and heating at 500 °C. The maximum thickness of the film obtained by one-run dip-coating using the sol containing trehalose was over 1000 nm. The film was an aggregate of alumina particles with a diameter of 20-40 nm and pores were interstices between the particles. The porosity of alumina film can be controlled in the range of 48-65 % by changing trehalose concentration in the dip-coating solution.

Abstract: A new photochromic ZrO2 precursor solution was prepared using zirconium tetra-n-butoxide, 4-(phenylazo)benzoic acid and ethyleneglycol monomethylether. The ZrO2 precursor solution was irradiated with ultraviolet light (UV) at room temperature. After that, UV-irradiated precursor solution was irradiated with visible light (Vis) at room temperature. UV-Vis spectra were measured before irradiation, after UV irradiation and Vis irradiation. Changes of UV-Vis spectra indicated that the new ZrO2 precursor including 4-(phenylazo)benzoic acid shows photochromism. The phenomena have synchronized with reversible photoisomerization of 4-(phenylazo)benzoic acid in the precursor. In addition, the difference of peak position originated from Zr-O CT transition between before UV irradiation and after UV irradiation increased with increasing the concentration of 4-(phenylazo)benzoic acid. Furthermore, the optimized structure of the new ZrO2 precursor was derived by density functional theory (DFT) calculation.

Abstract: To obtain porous alumina films, the precursor sol was prepared by hydrolysis of Al isopropoxide and then mixing with poly(ethylene glycol) (PEG). The porous alumina films were fabricated by dip-coating technique on glass substrates and heating at 500 °C. The film was composed of nano sized particles (30-50 nm). The maximum thickness of the film prepared by one-run dip-coating was ca. 1000 nm. The film had humidity-sensitive electrical resistance at room temperature.

Abstract: BaTiO3 films with thickness of ~1 2m were prepared by chemical solution deposition on LaNiO3/Pt/TiOx/SiO2/Si substrate with a thin highly (100)-oriented and high crystallinity BaTiO3 thin film (~140 nm) as a buffer layer. The BaTiO3 films prepared by using a 0.5 mol/L solution have high crystallinity and still show (100) preferred orientation. The electrical properties of the (100)-oriented BaTiO3 films prepared by this process have been studied. A dielectric constant of ~910 and a loss tangent of ~3.5% (1 kHz) were obtained. The remanent polarization (2 Pr) and coercive field (2 Ec) are 4.0 μC/cm2 and 35 kV/cm, respectively.

Abstract: The Y0.5Yb0.5MnO3 ferroelectrics/HfO2 stacking layer was constructed on Si(100) substrate through the chemical solution deposition. The HfO2 insulating layer crystallized on Si(100) substrates consisted of uniform grains and had smooth surface. The Y0.5Yb0.5MnO3 film prepared on the HfO2 insulator layer had preferred orientation along c-axis. The Y0.5Yb0.5MnO3 film consisted of uniform grains and had smooth surface. The clockwise C-V hysteresis induced by ferroelectric polarization switching was observed in the MFIS structure. The memory window of the MFIS structure was about 2 V and the retention time was over 105 s.

Abstract: A chemical solution deposition process for preparation of highly (100)-oriented Ba(Zr0.05Ti0.95)O3 films was developed. The orientation degree of Ba(Zr0.05Ti0.95)O3 thin films prepared by this process can reach up to 99.1%. The electrical properties of the (100)-oriented films prepared by this process have been studied. The Ba(Zr0.05Ti0.95)O3 films with a thickness of about 270 nm show a dielectric constant of ∼740 and a loss tangent of ∼3%. The remanent polarization (2Pr) and coercive field (2Ec) are 3.2 μC/cm2 and 34 kV/cm, respectively.