Tetsu Yonezawa

Room temperature deposition of a TiO2 thin film from aqueous peroxotitanate solution

A transparent, high purity, amorphous titanium dioxide thin film composed of densely packed nanometer-sized grains has been successfully deposited on a glass substrate at room temperature from an aqueous peroxotitanate solution using a simple, inexpensive, reproducible, and environmentally friendly method. The as-deposited thin film was 117 nm thick and composed of closely packed particles of 10–15 nm in diameter, but they aggregated into large grains of 50–100 nm in diameter. The aqueous peroxotitanate solution was obtained by dissolving metatitanic acid (H2TiO3) in a mixture of concentrated H2O2 and NH3·H2O. An anatase TiO2 thin film was obtained by heating the as-deposited thin film at 500 °C for 1 h in air. A chemical composition of TiO1.4(O2)0.5(OH)0.2·1.34H2O is proposed for the as-deposited thin film, based on XPS, FT-IR and TG-DTA data. Band gap energies of 3.20 eV for indirect transition and 3.63 eV for direct transition were obtained for the anatase TiO2 film.

Practical preparation of anionic mercapto ligand-stabilized gold nanoparticles and their immobilization

Abstract Gold nanoparticles stabilized by a water-soluble mercapto ligand (sodium 3-mercaptopropionate) were produced by a modified citrate reduction of HAuCl 4 . No rigorous cleanliness is needed and the reductant is decomposed to CO 2 . Stable aqueous dispersions of gold nanoparticles without any precipitation for several months could be obtained. The particle size can be controlled by the stabilizer/gold ratios. These gold nanoparticles were incorporated successfully into the interlayers of cast films of cationic bilayers by immersion of the film in gold nanoparticle dispersions.

Preparation of SrTiO3 thin films by the liquid phase deposition method

Successful preparation of strontium titanate (SrTiO3; STO) thin films has been realized by the liquid phase deposition method. The STO precursor solid thin films with close-packed grains smaller than 200 nm were fabricated from an aqueous solution of Sr(NO3)2/(NH4) 2 TiF6/H3BO3/1/1/3 (molar ratio) at 50 8C on a Si substrate. X-ray photoelectron spectroscopy analysis showed that the as-deposited film contained fluorine as an impurity, which could be completely eliminated by annealing at 500 8C in air, accompanying the crystallization of the as-deposited amorphous thin film into perovskite-type STO. # 2002 Elsevier Science B.V. All rights reserved.

Atomic scale flattening of organosilane self-assembled monolayer and patterned tin hydroxide thin films

Abstract We have succeeded in fabricating an atomic flattening surface of organosilane self-assembled monolayers (SAMs) on a Si substrate. In the present process, the octadecyltrichlorosilane (OTS) compound was selected as the starting material for the SAM. The OTS–SAM was formed by the reaction between the OTS molecules and the substrates, which were hydrogen terminated Si(001) (H:Si) and silica covered on Si(001) (SiO2/Si), at room temperature in a N2 atmosphere. The formation rate of the OTS–SAM onto H:Si was smaller than that on SiO2/Si. Interestingly, the hydrophobicity of the OTS–SAM was observed to increase the amount formed on H:Si in comparison with that on SiO2/Si. The photo reactivity of the SAMs formed on each substrate was also investigated by using ultraviolet (UV) irradiation in ambient air. Tin hydroxide thin films were site-selectively deposited on the patterned OTS–SAM/Si substrate in order to clarify the cleavage of the OTS–SAM by the UV irradiation.

Two-Dimensional Patterning of Nanoparticles Using Dissipative Structures

Abstract Two-dimensional regular patterns of nanoparticles were formed on solid substrate by casting colloidal dispersion. Periodic stripes were formed on mica surface parallel to the receding direction of casting solution. The thickness of each stripe was estimated to be comparable to that of monolayer of particles. From atomic force microscopy (AFM) and scanning electron microscopy (SEM), it was cleared that the monolayer of silica particles were hexagonally packed.