Yanfeng Gao

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.

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.

Band Gap Energy of SrTiO 3 Thin Film Prepared by the Liquid Phase Deposition Method

Band gap energies of SrTiO 3 (STO) thin film on glass substrates were studied in terms of annealing temperature. The STO thin film was fabricated by our newly developed method based on the combination of the Self-Assembled Monolayer(SAM) technique and the Liquid Phase Deposition(LPD) method. The as-deposited film demonstrated a direct band gap energy of about 3.65 eV, which further increased to 3.73 eV and 3.78 eV by annealing at 400 o C and 500 o C, respectively. The band gap energy saturated at about 3.70 eV for the crystallized film which was obtained by annealing at 600 -700 o C. The relatively large band gap energies of our crystallized films were due to the presence of minor amorphous phase, grain boundaries and oxygen vacancies generated by annealing in air.

Scanning electron microscopy and atomic force microscopy of Coscinodiscus granii frustules treated by the liquid phase deposition

The surface structures of Coscinodiscus granii frustules were investigated before and after liquid phase deposition (LPD) treatment. Scanning electron microscopy (SEM) images showed that the outer surface of the frustules was rapidly covered with a TiO2 layer within 6 h although the inner surface was not fully covered under the same condition. Comparison between the un-coated samples and the samples coated with metal prior to SEM observation provided valuable results to facilitate the understanding of the differences between the surface properties of the inner and outer frustule structures. Additionally, useful topographical information about the inner frustule surfaces was obtained by AFM imaging. The results of this investigation provide fundamental information about the process of LPD treatment onto frustule surfaces.