Transparent conducting thin films properties

At the same time, SWNT can be used at the top electrode (that needs to be transparent) as a replacement for the currently used thin films that are also electrical conductors. Typical conductive thin films used today are oxides such as fluorine-doped tin oxide (FTO), Al-doped zinc oxide, and the indium tin oxide (ITO) mentioned above. The disadvantages of these oxide films are that they require expensive deposition procedures at high vacuum, they have poor mechanical properties, and they are not transparent in the infrared. Another interesting difference is that transparent oxide conductors are n-type semiconductors. By contrast, nanotube networks act as p-type semiconductors, which could lead to new designs. 

Vollmer A, Feng XL, Wang X, Zhi LJ, Muellen K, Koch N, Rabe JP (2009) Electronic and structural properties of graphene-based transparent and conductive thin film electrodes. Appl Phys A Mater Sci Process 94 1-4... 

C. Mattevi, G. Eda, S. Agnoli, S. Miller, K.A. Mkhoyan, 0. Celik, et al., Evolution of electrical, chemical, and structural properties of transparent and conducting chemically derived graphene thin films, Advanced Functional Materials, 19 (2009) 2577-2583. 

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 ... 

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. 

In the following, each step will be described, both for the AP-CVD and for the LP-CVD cases. The results presented are focused on those properties of ZnO films that are useful for thin film solar cell applications, i.e., transparency, conductivity, and light scattering capability. The last part of paragraph 6.2 comments briefly on alternative methods of CVD processes that have been investigated for ZnO deposition (PE-CVD, photo-CVD,. ..). 

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. 

The introduction of bridging groups on the thiophene ring modifies the physical and chemical properties of the polymers obtained. The energy of the optical absorption is reduced in FEDOT, Fig. 9.2(k), and poly(ijothia-naphthalene), (PITN) (Wudl et al., 1984), so that in the conductive state thin films are transparent. PEDOT shows high electrochemical stability in the oxidised state and, when combined with poly(styrenesulphonic acid) counter ions, can be processed from aqueous solution. 

This chapter is intended to cover major aspects of the deposition of metals and metal oxides and the growth of nanosized materials from metal enolate precursors. Included are most types of materials which have been deposited by gas-phase processes, such as chemical vapor deposition (CVD) and atomic layer deposition(ALD), or liquid-phase processes, such as spin-coating, electrochemical deposition and sol-gel techniques. Mononuclear main group, transition metal and rare earth metal complexes with diverse /3-diketonate or /3-ketoiminate ligands were used mainly as metal enolate precursors. The controlled decomposition of these compounds lead to a high variety of metal and metal oxide materials such as dense or porous thin films and nanoparticles. Based on special properties (reactivity, transparency, conductivity, magnetism etc.) a large number of applications are mentioned and discussed. Where appropriate, similarities and difference in file decomposition mechanism that are common for certain precursors will be pointed out. 

Suspensions of polyacetylene were prepared as burrs or fibers (46) by using a vanadium catalyst. When the solvent was removed, films of polyacetylene were formed with densities greater than that prepared by the Shirakawa method. These suspensions were mixed with various fillers to yield composite materials. Coatings were prepared by similar techniques. Blends of polypyrrole, polyacetylene, and phthalocyanines with thermoplastics were prepared (47) by using the compounding techniques typically used to disperse colorants and stabilizers in conventional thermoplastics. Materials with useful antistatic properties were obtained with conductivities from 10" to 10" S/cm. The blends were transparent and had colors characteristic of the conducting polymer. For example, plaques containing frans-polyacetylene had the characteristic violet color exhibited by thin films of solid trans-polyacetylene. 

Indium-tin oxide (ITO) is indium oxide doped with tin oxide. Thin films of ITO have commercially valuable properties it is transparent, electrically conducting and reflects IR radiation. Applications of ITO are varied. It is used as a coating material for flat-panel computer displays, for coating architectural glass panels, and in electrochromic devices. Coating motor vehicle and aircraft windscreens and motor vehicle rear windows allows them to be electrically heated for de-icing... 

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]. 

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