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.

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Tin doped indium oxide thin films: Electrical properties

The photoinduced surface wettability conversion reactions of ZnO and TiO2 thin films were investigated by means of water contact angle measurement and X-ray photoelectron spectroscopy. Before ultraviolet (UV) illumination, ZnO and TiO2 films exhibited water contact angles of ∼109 and ∼54°, respectively. UV illumination turned both surfaces to highly hydrophilic with water contact angles smaller than 10°. Storage in the dark reconverted the highly hydrophilic films to their original states. Reversible surface wettability conversion reactions were achieved by alternate UV illumination and storage in the dark on both the films. The similar behaviors of wettability conversion observed on ZnO and TiO2 surfaces suggest that they follow a similar conversion mechanism. Preferential adsorption of water molecules on the photogenerated surface defective sites is ascribed to the formation of highly hydrophilic ZnO and TiO2 surfaces. Achievement of highly hydrophilic ZnO and TiO2 surfaces by high-temperature annealing...

Photoinduced Surface Wettability Conversion of ZnO and TiO2 Thin Films

Meeting the growing global energy demand is one of the important challenges of the 21st century. Currently over 80% of the world's energy requirements are supplied by the combustion of fossil fuels, which promotes global warming and has deleterious effects on our environment. Moreover, fossil fuels are non-renewable energy and will eventually be exhausted due to the high consumption rate. A new type of alternative energy that is clean, renewable and inexpensive is urgently needed. Several candidates are currently available such as hydraulic power, wind force and nuclear power. Solar energy is particularly attractive because it is essentially clean and inexhaustible. A year's worth of sunlight would provide more than 100 times the energy of the world's entire known fossil fuel reserves. Photocatalysis and photovoltaics are two of the most important routes for the utilization of solar energy. However, environmental protection is also critical to realize a sustainable future, and water pollution is a serious problem of current society. Photocatalysis is also an essential route for the degradation of organic dyes in wastewater. A type of compound with the defined structure of perovskite (ABX3) was observed to play important roles in photocatalysis and photovoltaics. These materials can be used as photocatalysts for water splitting reaction for hydrogen production and photo-degradation of organic dyes in wastewater as well as for photoanodes in dye-sensitized solar cells and light absorbers in perovskite-based solar cells for electricity generation. In this review paper, the recent progress of perovskites for applications in these fields is comprehensively summarized. A description of the basic principles of the water splitting reaction, photo-degradation of organic dyes and solar cells as well as the requirements for efficient photocatalysts is first provided. Then, emphasis is placed on the designation and strategies for perovskite catalysts to improve their photocatalytic activity and/or light adsorption capability. Comments on current and future challenges are also provided. The main purpose of this review paper is to provide a current summary of recent progress in perovskite materials for use in these important areas and to provide some useful guidelines for future development in these hot research areas.

Research progress of perovskite materials in photocatalysis- and photovoltaics-related energy conversion and environmental treatment.

The influence of postdeposition annealing on the structural and optical properties of rf sputtered insulating zinc oxide films has been investigated. The as‐grown films deposited on quartz substrates were highly c‐axis oriented and in a state of stress. These films become almost stress free after a postdeposition annealing treatment at 673 K for 1 h in air. Above 673 K, a process of coalescence was observed which causes major grain growth resulting in microcrack formation and surface roughness. The refractive index shows a strong frequency dispersion below the interband absorption edge. The optical dispersion data have been fitted to (1) a single oscillator model and (2) the Pikhtin–Yas’kov model. The origin of optical dispersion at different annealing temperatures has been discussed in the light of these models. A packing density of more than 99% is estimated in the film annealed at 673 K, indicating that these films are almost void free.

Influence of postdeposition annealing on the structural and optical properties of sputtered zinc oxide film

This report describes the concentrating solar power (CSP) systems using solar absorbers to convert concentrated sunlight to thermal electric power. It is possible to achieve solar absorber surfaces for efficient photothermal conversion having high solar absorptance (a) for solar radiation and a low thermal emittance (e) at the operational temperature. A low reflectance (?'' 0) at wavelengths (?) 3 mm and a high reflectance (?'' 1) at l 3 mm characterize spectrally selective surfaces. The operational temperature ranges of these materials for solar applications can be categorized as low temperature (T 400 C). High- and mid-temperature applications are needed for CSP applications. For CSP applications, the ideal spectrally selective surface would be low-cost and easy to manufacture, chemically and thermally stable in air at elevated operating temperatures (T= 500 C), and have a solar absorptance= 0.98 and a thermal emittance= 0.05 at 500 C.

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M.P. dos Santos

Papers

Investigations of titanium oxide films deposited by d.c. reactive magnetron sputtering in different sputtering pressures

Properties of indium tin oxide films prepared by rf reactive magnetron sputtering at different substrate temperature

The effect of substrate temperature on the properties of d.c. reactive magnetron sputtered titanium oxide films

Study of the structural properties of ZnO thin films by x-ray photoelectron spectroscopy

Optical and structural properties of vanadium pentoxide films prepared by d.c. reactive magnetron sputtering