Oxide thin films, depositing from solution

Clem, P. G. Jeon, N.-L. Nuzzo, R. G. Payne, D. A. 1997. Monolayer-mediated deposition of tantalum (V) oxide thin film structures from solution precursors. J. Am. Ceram. Soc. 80 2821-2827. 

Usually the functional moiety is covalently linked to the conjugated backbone, but it can be sometimes added to ECP as a dopant when it is under an ionic form e.g., sulfonated P-cyclodextrins have been successfiilly incorporated in one step as anionic dopants in PPy by electropolymerization [230]. In some cases, electrochemistry can be combined to chemical reactions to derive functional ECPs functional PANI materials can be obtained from the reduction of the emeraldine form by alkylthiols [255] and the functionality degree on the PANI backbone can be monitored by successive oxidation-reduction cycles various functionalized PANIs can also be synthesized through electrophilic substitution or nucleophilic addition reactions [256]. For example. Figure 18.10 shows the similar electrochemical behaviors of sulfonated PANI made from reduction of emeraldine by sulfite salt followed by reoxidation, compared to thin films deposited from solution of highly sulfonated PANIs. 

Pauporte and Lincot [157, 158] have developed the preparation of zinc oxide thin films by cathodic deposition at 70° C from chloride aqueous solutions with dissolved zinc(II) chloride and hydrogen peroxide. 

Liquid phase deposition (LPD) process is the formation of oxide thin films from an aqueous solution of a metal-fluoro complex which is slowly hydrolyzed by adding fluoride scavengers such as boric acid or aluminum metal [47], namely... 

Chemical deposition from solutions of chalcogenide compound thin films finds its origin more than one century ago when for instance Emerson-Reynolds, in 1884 [1], reported that thiourea is easily desulfurated by certain metallic oxides and hydroxides (silver, mercury, lead) to form the corresponding sulfide. When the reaction proceeds in basic solutions, a specular and strongly adherent layer is formed on the sides of the vessel, in parallel with the precipitation in the volume of the solution, according to the global reaction ... 

Schlettwein, Yoshida, and Lincot provide a critical review of the research literature on porous zinc oxide sensitized by organic dyes, and the potential use of these materials for the development of large-scale photovoltaic solar cells. An introduction is provided to the electrodeposition of zinc oxide thin films, their means of sensitization by a variety of organic molecules, and their preparation by one-step deposition from solutions containing water-soluble dyes to produce hybrid materials suitable for solar cell. The advantages of various substrates for large-scale cells are discussed for plastic and textile materials. 

FIGURE 18.10 Cyclic voltammetry (CV) of thin films of highly sulfonated polyaniline deposited from solution (HSPAN) and similar material synthesized by reduction of emeraldine salt by sulphite ion followed by oxidation (ES + HS03 - - O2). (Reprinted from Barbero, C., H.l. Salavagjone, D.E Acevedo, D.E. Grumelli, F. Garay, G.A. Planes, G.M. Morales, and M.C. Miras. Electrochim. Acta., 49, 3671—3686, 2004. With permission.)... 

Thin films prepared using the sol-gel method are usually amorphous before heat treatment. High-temperature heat treatment is generally required for the films crystallization and densification of the films. For application of thin films to substrates with low thermal stability such as polymer substrates, lowering of the crystallization temperature is necessary. Consequently, many researchers have recently reported formation of oxide crystals, such as T1O2, Sn02 and ZnO, at low temperatures [1, 2]. For example, the preparation of various oxide thin films from aqueous metal-fluoro complex solutions using the liquid phase deposition method... 

These metal-amine complexes are stable toward moisture and are soluble in organic solvents, leading to liquid precursors with appropriate viscosities for their deposition on substrates. Metal oxide thin films have been prepared from these amine-based precursors, including complex oxide thin films of titanium or bismuth-based perovskites, among others. The molecular structures of the titanium-amine and bismuth-amine complexes synthesized in a solution are shown in Scheme 27.6 [25-27]. In addition, the dative bond from the nitrogen toward the metallic center incorporates new functionalities into these types of molecules, such as photosensitivity, that can be used for nonconventional methods of synthesis of metal oxide thin films. 

A large number of electrolytic treatments of magnesium, anodic or a.c., have been developed, in which adherent white or grey films consisting of fluoride, oxide, hydroxide, aluminate or basic carbonate are deposited from alkaline solutions containing caustic alkali, alkali carbonates, phosphates, pyrophosphates, cyanides, aluminates, oxalates, silicates, borates, etc. Some films are thin, and some are relatively thick. All are more or less absorbent and act as good bases for paint, though none contributes appreciable inhibition. All can, however, absorb chromates with consequent improvement of protective efficiency. 

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