The semiconductor ZnO has gained substantial interest in the research community in part because of its large exciton binding energy (60meV) which could lead to lasing action based on exciton recombination even above room temperature. Even though research focusing on ZnO goes back many decades, the renewed interest is fueled by availability of high-quality substrates and reports of p-type conduction and ferromagnetic behavior when doped with transitions metals, both of which remain controversial. It is this renewed interest in ZnO which forms the basis of this review. As mentioned already, ZnO is not new to the semiconductor field, with studies of its lattice parameter dating back to 1935 by Bunn [Proc. Phys. Soc. London 47, 836 (1935)], studies of its vibrational properties with Raman scattering in 1966 by Damen et al. [Phys. Rev. 142, 570 (1966)], detailed optical studies in 1954 by Mollwo [Z. Angew. Phys. 6, 257 (1954)], and its growth by chemical-vapor transport in 1970 by Galli and Coker [Appl. Phys. ...

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A comprehensive review of zno materials and devices

This critical review shows the basis of photocatalytic water splitting and experimental points, and surveys heterogeneous photocatalyst materials for water splitting into H2 and O2, and H2 or O2 evolution from an aqueous solution containing a sacrificial reagent Many oxides consisting of metal cations with d0 and d10 configurations, metal (oxy)sulfide and metal (oxy)nitride photocatalysts have been reported, especially during the latest decade The fruitful photocatalyst library gives important information on factors affecting photocatalytic performances and design of new materials Photocatalytic water splitting and H2 evolution using abundant compounds as electron donors are expected to contribute to construction of a clean and simple system for solar hydrogen production, and a solution of global energy and environmental issues in the future (361 references)

Heterogeneous photocatalyst materials for water splitting

Transparent electronic devices formed on flexible substrates are expected to meet emerging technological demands where silicon-based electronics cannot provide a solution. Examples of active flexible applications include paper displays and wearable computers1. So far, mainly flexible devices based on hydrogenated amorphous silicon (a-Si:H)2,3,4,5 and organic semiconductors2,6,7,8,9,10 have been investigated. However, the performance of these devices has been insufficient for use as transistors in practical computers and current-driven organic light-emitting diode displays. Fabricating high-performance devices is challenging, owing to a trade-off between processing temperature and device performance. Here, we propose to solve this problem by using a novel semiconducting material—namely, a transparent amorphous oxide semiconductor from the In-Ga-Zn-O system (a-IGZO)—for the active channel in transparent thin-film transistors (TTFTs). The a-IGZO is deposited on polyethylene terephthalate at room temperature and exhibits Hall effect mobilities exceeding 10 cm2 V-1 s-1, which is an order of magnitude larger than for hydrogenated amorphous silicon. TTFTs fabricated on polyethylene terephthalate sheets exhibit saturation mobilities of 6–9 cm2 V-1 s-1, and device characteristics are stable during repetitive bending of the TTFT sheet.

Room-temperature fabrication of transparent flexible thin-film transistors using amorphous oxide semiconductors

2.3. Evaluation of Photocatalytic Water Splitting 6507 2.3.1. Photocatalytic Activity 6507 2.3.2. Photocatalytic Stability 6507 3. UV-Active Photocatalysts for Water Splitting 6507 3.1. d0 Metal Oxide Photocatalyts 6507 3.1.1. Ti-, Zr-Based Oxides 6507 3.1.2. Nb-, Ta-Based Oxides 6514 3.1.3. W-, Mo-Based Oxides 6517 3.1.4. Other d0 Metal Oxides 6518 3.2. d10 Metal Oxide Photocatalyts 6518 3.3. f0 Metal Oxide Photocatalysts 6518 3.4. Nonoxide Photocatalysts 6518 4. Approaches to Modifying the Electronic Band Structure for Visible-Light Harvesting 6519

Semiconductor-based Photocatalytic Hydrogen Generation

We report the fabrication of transparent field-effect transistors using a single-crystalline thin-film transparent oxide semiconductor, InGaO 3 (ZnO) 5 , as an electron channel and amorphous hafnium oxide as a gate insulator. The device exhibits an on-to-off current ratio of ∼10 6 and a field-effect mobility of ∼80 square centimeters per volt per second at room temperature, with operation insensitive to visible light irradiation. The result provides a step toward the realization of transparent electronics for next-generation optoelectronics.

http://science.sciencemag.org/content/sci/300/5623/1269.full.pdf

Thin-Film Transistor Fabricated in Single-Crystalline Transparent Oxide Semiconductor

It was demonstrated that the oxyfluoride NbO2F with an ReO3-type structure is a promising electrochromic material with wide band gap. Measurement of diffuse reflectance spectra revealed the optical band gap of NbO2F (∼3.1 eV) to be wider than that of WO3 (∼2.6 eV). It was rendered electron conductive by heating at 770 K in the presence of Pt powder in H2. Electrical conductivity for the blue-colored sintered sample of NbO2F obtained was 6×10−3 S cm−1 at 300 K, and a temperature dependence showed the semiconductive behaviors. A reversible electrochromism between pale-blue and deep-blue-color was found in H2SO4 and Na2SO4 aqueous solution.

NbO2F: An oxyfluoride phase with wide band gap and electrochromic properties

Electro-conductive oxides showing excellent electro-conductivity, electrodes using the electro-conductive oxide and methods for manufacturing the same are described. The electro-conductive oxides are represented by the general formula: M(1)x M(2)y Inz O.sub.(x+3y/2+3s/2)-d. The above electro-conductive oxides show not only excellent electro-conductivity but also excellent transparency all over the visible region and therefore they are particularly useful as, for example, electrodes for liquid crystal displays, EL displays and solar cells, which require light transmission.

Electro-conductive oxide electrodes and devices using the same

PROBLEM TO BE SOLVED: To solve the problem that the evaporation of ZnO having high vapor pressure occurs vigorously, thereby making it difficult to control the composition, and homogeneous superlattice cannot be formed when a homologous series M 1 M 2 O 3 (ZnO) m is grown by a thin film growth method. SOLUTION: The natural superlattice homologous single crystal thin film comprises double oxides which are epitaxilally grown on a ZnO epitaxial thin film formed on a single crystal substrate or the single crystal substrate from which the thin film has disappeared or a ZnO single crystal and is expressed by formula: M 1 M 2 O 3 (ZnO) m (wherein, M 1 is at lest one of Ga, Fe, Sc, In, Lu, Yb, Tm, Er, Ho and Y; M 2 is at least one of Mn, Fe, Ga, In and Al; and m is a natural number which is ≥1). The homologous single crystal thin film is manufactured by depositing the double oxide films and subjecting the stacked films to heat-diffusion treatment. The natural superlattice homologous single crystal thin film is used for an optical device, an electronic device, an X-ray optical device of the like. COPYRIGHT: (C)2003,JPO

Natural superlattice homologous single crystal thin film and method of manufacturing the same

A low-resistance ITO thin film having a resistivity on the order of, or lower than 10−4 Ωcm, and a method for manufacturing such a film are disclosed The ITO thin film is manufactured by depositing ITO on a crystalline substrate by pulsed laser deposition, low-voltage sputtering, oxygen cluster beam deposition, chemical vapor deposition, metal organic chemical vapor deposition, metal organic chemical vapor deposition—atomic layer deposition, or molecule beam epitaxy

Low-resistance ITO thin film and method for manufacturing such a film

Transparent conductive oxides of ITO, ZnO, β-Ga2O3, and CuGaO2 and SrCu2O2 were grown on single crystal substrates of α-Al2O3 and YSZ by pulsed-laser deposition, and their crystallinity was evaluated by using high-resolution X-ray diffraction and electron microscope Heteroepitaxial growth was observed in spite of relatively large lattice mismatches between film and substrate A few disordered layers were generated automatically at film/substrate boundary, played buffer layer to suppress propagation of edge dislocations

Masahiro Orita

Papers

NbO2F: An oxyfluoride phase with wide band gap and electrochromic properties

Electro-conductive oxide electrodes and devices using the same

Natural superlattice homologous single crystal thin film and method of manufacturing the same

Low-resistance ITO thin film and method for manufacturing such a film

Epitaxial growth of transparent conductive oxides