Zinc oxide optical properties

Zinc oxide is certainly not unique in exhibiting a strong correlation between adsorption and its electrical and optical properties. 

Since the first synthesis of mesoporous materials MCM-41 at Mobile Coporation,1 most work carried out in this area has focused on the preparation, characterization and applications of silica-based compounds. Recently, the synthesis of metal oxide-based mesostructured materials has attracted research attention due to their catalytic, electric, magnetic and optical properties.2 5 Although metal sulfides have found widespread applications as semiconductors, electro-optical materials and catalysts, to just name a few, only a few attempts have been reported on the synthesis of metal sulfide-based mesostructured materials. Thus far, mesostructured tin sulfides have proven to be most synthetically accessible in aqueous solution at ambient temperatures.6-7 Physical property studies showed that such materials may have potential to be used as semiconducting liquid crystals in electro-optical displays and chemical sensing applications. In addition, mesostructured thiogermanates8-10 and zinc sulfide with textured mesoporosity after surfactant removal11 have been prepared under hydrothermal conditions. 

In this book the chemical, structural, optical, electrical, and interface properties of zinc oxide are summarized with special emphasis on the use of ZnO as transparent conductive electrode in thin film solar cells. This application has a number of requirements, which can be fulfilled by ZnO ... 

In this chapter some of the presently known optical properties of zinc oxide are reviewed. In particular, the anisotropic dielectric functions (DFs) of ZnO and related compounds from the far-infrared (FIR) to the vacuum-ultraviolet (VUV) spectral range are studied. Thereupon, many fundamental physical parameters can be derived, such as the optical phonon-mode frequencies and their broadening values, the free-charge-carrier parameters, the static and high-frequency dielectric constants, the dispersion of the indices of refraction within the band-gap region, the fundamental and above-band-gap band-to-band transition energies and their excitonic contributions. 

It should be mentioned that zinc oxide is also used between silicon and the metallic contact as a part of the back reflector to improve its optical properties and to act as a diffusion barrier [12,13]. A layer thickness between about 60 and 100 nm is usually sufficient here, and there are no strict requirements for... 

Kim, K. H., Park, K. C. and Ma, D. Y. (1997). Structural, electrical and optical properties of aluminum doped zinc oxide films prepared by radio frequency magnetron sputtering. J. Appl. Phys. 81(12), 7764-7772. 

J. P. Kuz mina, V.A. Nikitenko, Zinc Oxide. Production and Optical Properties [in Russian], Moscow (1984). 

Recently, there has been a significant increase of research in the field of zinc oxide. This is mainly driven by its extraordinary electrical and optical properties that enable a variety of applications ranging from piezoelectrical... 

The obtained results allow to study the electronic structure and optical properties of ZnO crystal on the basis of conceptually deeper and more detailed background, than it was previously available on integral reflectivity spectra, and to base theoretical calculations of the properties of zinc oxide upon new foundations. 

There are several different metal oxides with optical band gaps of 2.5 to 4 eV, which are useful for transparent conducting oxide (TCO) coatings. The most common of these are tin-doped indium oxide (ITO), fluorine or antimony-doped tin oxide and doped zinc oxides. The preparation and physical properties of these materials prepared by CVD will be discussed. 

Critical properties of TCO coatings are electrical resistance and transparency [3], but for solar cell applications very often texture and large haze factors, i.e., ratio of diffuse to total transmission, have similar importance. Large haze factors have been shown to influence positively the efficiency of silicon solar cells, because the reflection at the TCO-silicon interface is reduced and the scattering increases the pathway of light inside the active material. The preparation and characteristics of several TCO materials have been reviewed by Chopra et al. [92] and Dawar and Joshi [93]. The optical and electrical properties of ITO and aluminum doped zinc oxide have been studied in detail by Granqvist and coworkers [94, 95], but these films were prepared by sputtering and not by CVD. Very recently they also published an overview of transparent conductive electrodes for electrochromic devices [7]. 

Transparent conductive coatings combine high optical transmission with good electrical conductivity. The existence of both properties in the same material is, from the physics point of view, not trivial and is only possible with certain semi-conductors like indium oxide, tin oxide, cadmium oxide, and with thin gold and silver films, e.g. [157]. Particularly antimony or fluorine doped tin oxide (ATO, FTO), tin doped indium oxide (ITO), and aluminium, indium, or boron doped zinc oxide (AZO, IZO, BZO) are of technical importance [157a]. 

Potential-dependent optical properties in nanoporous zinc oxide electrodes... 

In this paper, capabilities of a simple and low-cost synthesis method based on the pulsed discharge submerged in water for fabrication of zinc oxide nanopowders are discussed. This technique has the additional advantage of eliminating the need for high temperatures and for chemical precursors and it offers a good control over the particles size. The structural and optical properties of prepared nanoparticles have been studied and optimal conditions for preparation of high quality ZnO nanopowder without metallic zinc contamination have been found. 

Sebok, D., Szabo, T, Dekany, I. 2009. Optical properties of zinc peroxide and zinc oxide multilayer nanohybrid films. Applied Surface Science 255 6953-6962. 

---