Photocatalysis has recently become a common word and various products using photocatalytic functions have been commercialized. Among many candidates for photocatalysts, TiO2 is almost the only material suitable for industrial use at present and also probably in the future. This is because TiO2 has the most efficient photoactivity, the highest stability and the lowest cost. More significantly, it has been used as a white pigment from ancient times, and thus, its safety to humans and the environment is guaranteed by history. There are two types of photochemical reaction proceeding on a TiO2 surface when irradiated with ultraviolet light. One includes the photo-induced redox reactions of adsorbed substances, and the other is the photo-induced hydrophilic conversion of TiO2 itself. The former type has been known since the early part of the 20th century, but the latter was found only at the end of the century. The combination of these two functions has opened up various novel applications of TiO2, particularly in the field of building materials. Here, we review the progress of the scientific research on TiO2 photocatalysis as well as its industrial applications, and describe future prospects of this field mainly based on the present authors' work.

https://www.jsap.or.jp/jsapi/Pdf/Number14/04_JJAP-IRP.pdf

TiO2 Photocatalysis: A Historical Overview and Future Prospects

A novel amorphous oxide applicable, for example, to an active layer of a TFT is provided. The amorphous oxide comprises microcrystals.

Amorphous oxide and field effect transistor

Pt/TiO2 nanosheets with exposed (001) facets were fabricated by a simple hydrothermal route in a Ti(OC4H9)4-HF-H2O mixed solution followed by a photochemical reduction deposition of Pt nanoparticles on TiO2 nanosheets under xenon lamp irradiation. The prepared samples were characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, nitrogen adsorption−desorption isotherms, UV−vis diffuse reflectance spectroscopy, and photoluminescence (PL) spectroscopy. Production of •OH radicals on the TiO2 surface was detected by the PL technique using coumarin as a probe molecule. The effects of Pt loading on the rates of photocatalytic hydrogen production of the as-prepared samples in ethanol aqueous solution were investigated and discussed. The results showed that the photocatalytic hydrogen production rates of TiO2 nanosheets from the ethanol aqueous solutions were significantly enhanced by loaded Pt on the TiO2 nanosheets, and the latter with a 2 wt % of deposited Pt exhi...

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Hydrogen Production by Photocatalytic Water Splitting over Pt/TiO2 Nanosheets with Exposed (001) Facets

Nitrogen-doped titanium dioxide as visible-light-sensitive photocatalyst: designs, developments, and prospects.

Tin doped indium oxide (ITO) films are highly transparent in the visible region, exhibiting high reflectance in the infrared region, and having nearly metallic conductivity. Owing to this unusual combination of electrical and optical properties, this material is widely applied in optoelectronic devices. The association of these properties in a single material explains the vast domain of its applicability and the diverse production methods which have emerged. Although the different properties of tin doped indium oxide in the film form are interdependent, this article mainly focuses on the electrical aspects. Detailed description of the conduction mechanism and the main parameters that control the conductivity is presented. On account of the large varieties and differences in the fabrication techniques, the electrical properties of ITO films are discussed and compared within each technique.

/pdf/tin-doped-indium-oxide-thin-films-electrical-properties-1emmfeswwg.pdf

Tin doped indium oxide thin films: Electrical properties

Origin of characteristic grain-subgrain structure of tin-doped indium oxide films

Tin-doped indium oxide (ITO) films were deposited on soda-lime glass plates without substrate heating by dc magnetron sputtering. Crystallinity and electrical properties of the films were investigated by X-ray diffraction and Hall-effect measurements, which showed clear dependence on target–substrate distance (T–S) and on total gas pressure (Ptot) during deposition. Degradation in crystallinity was observed at relatively high or low Ptot, where the upper or lower Ptot level for depositing films with high crystallinity was increased with decreasing T–S. Based on a hard sphere collision model, the crystallinity of the films was considered to be strongly affected both by the kinetic energy of sputtered In (or Sn) particles and by the bombardment of high energy particles arriving at the growing film surface. The former could enhance the crystallinity, whereas the latter degraded both the crystallinity and conductivity. Such degradation in electrical properties was mainly due to a decrease in carrier density.

https://iopscience.iop.org/article/10.1143/JJAP.38.2921/pdf

Electrical and Structural Properties of Tin-Doped Indium Oxide Films Deposited by DC Sputtering at Room Temperature

Hydrophobic drawings on hydrophilic surfaces of single crystalline titanium dioxide : surface wettability control by mechanochemical treatment

Tin-doped and undoped amorphous indium oxide films were prepared by dc magnetron sputtering without substrate heating at relatively high total gas pressures and relatively large target-substrate distance. The structural and electrical properties of these films were investigated by X-ray diffraction and Hall-effect measurements. The amorphous tin-doped indium oxide (a-ITO) films were crystallized at a temperature about 30°C higher than that for amorphous indium oxide (a-IO) films.

https://iopscience.iop.org/article/10.1143/JJAP.38.5224/pdf

Preparation and Crystallization of Tin-doped and Undoped Amorphous Indium Oxide Films Deposited by Sputtering

Oriented thin‐film tin‐doped indium oxide (ITO) was heteroepitaxially grown on optically polished (100) or (111) planes of single‐crystalline yttria‐stabilized zirconia (YSZ) substrates using e‐beam evaporation or dc magnetron sputtering techniques. Pole figure x‐ray diffraction analyses revealed that the heteroepitaxial relations were (001)ITO∥(001)YSZ, [100]ITO∥[100]YSZ, and (111)ITO∥(111)YSZ, [110]ITO∥[110]YSZ, respectively. X‐ray rocking curve analyses and Rutherford backscattering spectrometry revealed that the e‐beam evaporated heteroepitaxial ITO films had much higher crystallinity than the one deposited by dc magnetron sputtering. Both carrier density and Hall mobility of the e‐beam evaporated heteroepitaxial films showed steady increases in a wide temperature range, which could be interpreted in terms of the increasing Sn‐doping efficiency caused by the improvement of the crystallinity of In2O3 host lattice, and hence the decreasing Sn‐based neutral scattering centers.

Masayuki Kamei

Papers

Origin of characteristic grain-subgrain structure of tin-doped indium oxide films

Electrical and Structural Properties of Tin-Doped Indium Oxide Films Deposited by DC Sputtering at Room Temperature

Hydrophobic drawings on hydrophilic surfaces of single crystalline titanium dioxide : surface wettability control by mechanochemical treatment

Preparation and Crystallization of Tin-doped and Undoped Amorphous Indium Oxide Films Deposited by Sputtering

Electrical properties of heteroepitaxial grown tin‐doped indium oxide films