Papers by Author: Kazuyuki Suzuki

Abstract: The HfO2 films were prepared on the ITO/polyimide substrate using alkoxy-derived precursor solutions at low temperature. The HfO2 films prepared by UV-assisted process using the precursor solution modified with diethanolamine had smooth surface and RMS roughness values of HfO2 film were 1.2nm. The electrical properties of HfO2 films were improved by optimization of preparation condition. The leakage current density at 1V was below 10-5A/cm2. The dielectric constant was about 20. The loss tangent was below 0.1.

Abstract: The HfO2 films prepared from alkoxy-derived precursor solution chemically modified with diethanolamine. The effects of UV irradiation on the HfO2 films were investigated. The UV irradiation using low pressure mercury lamp (LPML) was effective for the organics decomposition in the film and densification. The uniform and smooth HfO2 films were obtained. The refractive index of HfO2 films was enhanced.

Abstract: Various BaTiO3 thin films were fabricated at 650oC by using different conditions such as the heating rate and alkoxy-derived gel-film thickness. In this study, the spin-coating and calcination step were repeated several times to control the gel-films thickness. And then the one-sintering was carried out with various heating rates. BaTiO3 films with perovskite phase were obtained by using the heating rate of 100oC/sec and the surface morphology became rough with increase of gel-film thickness. We considered that the change of root mean square (rms) roughness and cross-sectional profiles by various heating rates was caused by densification.

Abstract: HfO2 precursor solutions were prepared by modification of alkoxide for patterning of HfO2 films. The HfO2 dots were patterned on Si substrate by inkjet printing method. The electrical properties of HfO2 films prepared by inkjet printing method were almost same as the properties of the HfO2 films prepared by spin-coating method. Additionally, the HfO2 nanostructures were successfully patterned by nanoimprint method using the chemically-modified alkoxy-derived precursor solution.

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.