Conducting materials, optically transparent

The interest in the synthesis and properties of delafossite structured compounds that have the general formula of ABO2 have grown due to their p-type conductivity and optical transparency. The application of ultrasound for the synthesis of ternary oxide AgMC>2 (M = Fe, Ga) has been investigated by Nagarajan and Tomar [44]. Above materials were obtained in crystalline form within 40-60 min of sonication. 

Transparent conducting oxides are widely used as electrodes in thin film optoelectronic devices as solar cells and light emitting diodes because of their transparency for visible light and their high electrical conductivity. Highest optical transparency and electrical conductivity are thus key aspects for such applications. Most work on TCO electrodes is, therefore, dedicated to find deposition parameters, which improve these material parameters. In addition, contact properties are essential for the application of TCOs as electrodes. 

LEDs require both electronic conductivity and optical transparency in one of the electrodes used to drive the device. The classic transparent electrode material is ITO, used long before conjugated polymers were considered for electronic devices. However, ITO is not printable (with the exception of a few recently developed commercial inks with relatively low conductivity), and producing ITO on flexible substrates is one of the largest costs involved in producing LEDs and similar devices. An example of ITO on flexible plastic (as used by Add-Vision Inc.) is found in Figure 4.4a. 

When done properly, systematic studies of sol-gel synthesis and processing can facilitate the search for new materials, particularly silica aerogels, with desired properties such as low thermal conductivity, high optical transparency, improved mechanical properties, or reduced dust release behavior. 

BeryUium is used in sateUite stmctures in the form of both sheet and extmded tubing and is a very important material for aU types of space optics. BeryUium oxide ceramic apphcations take advantage of high room temperature thermal conductivity, very low electrical conductivity, and high transparency to microwaves in microelectronic substrate apphcations. 

Figure 33.1a illustrates the idea of the smart window. In this device a layer of electrochromic material and a layer of a transparent ion-conducting electrolyte are sandwiched between two optically transparent electrodes (OTEs). Indium-doped tin oxide on glass is used most commonly as the OTE. This material has very low... 

The majority of the materials we use and handle every day are solid. We take advantage of their physical properties in manifold ways. The properties are intimately related to the structures. In the following we will deal only briefly with a few properties that are directly connected with some structural aspects. Many other properties such as electrical and thermal conductivity, optical transparency and reflectivity, color, luminescence etc. require the discussion of sophisticated theories that are beyond the scope of this book. 

In IMS, supportive materials, whose surfaces are coated with conductive materials, are used in principal. In the simplest way, the tissue slices can be placed on a metal MALDI plate directly.9 In this case, however, the target plate must be cleaned carefully after the measurement is over. Currently, the method commonly used is that samples are prepared on a disposable plastic sheet or a glass slide coated with series of conductive materials. In particular, a plastic sheet (ITO sheet) or glass slide (ITO glass slide available from Bruker Daltonics K.K., Billerica, MA, or Sigma, St. Louis, MO) coated with ITO (indium-tin oxide) is useful because it has superior optical transparency... 

In a typical spectroelectrochemical measurement, an optically transparent electrode (OTE) is used and the UV/vis absorption spectrum (or absorbance) of the substance participating in the reaction is measured. Various types of OTE exist, for example (i) a plate (glass, quartz or plastic) coated either with an optically transparent vapor-deposited metal (Pt or Au) film or with an optically transparent conductive tin oxide film (Fig. 5.26), and (ii) a fine micromesh (40-800 wires/cm) of electrically conductive material (Pt or Au). The electrochemical cell may be either a thin-layer cell with a solution-layer thickness of less than 0.2 mm (Fig. 9.2(a)) or a cell with a solution layer of conventional thickness ( 1 cm, Fig. 9.2(b)). The advantage of the thin-layer cell is that the electrolysis is complete within a short time ( 30 s). On the other hand, the cell with conventional solution thickness has the advantage that mass transport in the solution near the electrode surface can be treated mathematically by the theory of semi-infinite linear diffusion. 

The development of electrodes that exhibit optical transparency has enabled spectral observations to be made directly through the electrode simultaneously with electrochemical perturbations [19-21]. These electrodes typically consist of a very thin film of conductive material such as Pt, Au, carbon, or a semiconductor such as doped tin oxide that is deposited on a glass or quartz substrate. Miniature metal screens, minigrid electrodes in which the presence of very small holes (6-40 fim) lends transparency, have also been used. Optically transparent electrodes (OTE) and the cells that incorporate them are discussed in Chapters 9 and 11. 

Film electrodes are generally fabricated from conducting or semiconducting materials, which may be deposited as a result of either a physical or a chemical process (or some combination) onto a suitable substrate, which is typically an insulator. Key factors governing the desired thickness of the film are the electrical resistivity (p) or conductivity (k = 1/p) of the film material, which is a practical consideration in almost all cases, and the optical transparency or reflectance of the material if optical transmission or reflection is also desired. The optimum film thickness for an application involving both electrical and optical considerations will require a trade-off, since a decrease in resistivity (usually desirable) normally is also accompanied by a decrease in light transmission (undesirable for an optically transparent electrode). 

The obtaining of tin(IV) alkoxides was first reported in a well-known publication by Meerwein and Bersin [1101] devoted to bimetallic alkoxides. At the end of the 1950s Bradley [222] and Make [1049] practically simultaneously devoted the synthetic approaches to and described the properties of nearly all major representatives of the Sn(OR)4homologous series. During the last 10 to 20 years interest in these compounds was renewed due to the prospect of their application in the synthesis of optically transparent and conducting films based on Sn02, and also of related ceramic materials. The alkoxides of Sn(IV) were considered in detail in a review by Hampden-Smith etal. [702],... 

In addition to silicon and metals, a third important element being deposited as thin films is diamond (Celii and Butler, 1991 May, 2000). For many years, diamonds were synthesized by a high pressure/high temperature technique that produced bulk diamonds. More recently, the interest in diamonds has expanded to thin films. Diamond has a slew of properties that make it a desired material in thin-film form hardness, thermal conductivity, optical transparency, chemical resistance, electrical insulation, and susceptibility to doping. Thin film diamond is prepared using chemical vapor deposition, and we examine the process in some detail as a prototypical chemical vapor example. Despite its importance and the intensity of research focused on diamond chemical vapor deposition, there remains uncertainty about the exact mechanism. 

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