Thin Film Preparation Methods

A principal advantage of organic molecules in general and polymers in particular consists on their versatility and ease in processability. Depending on the nature of polymer itself, its chemical structure, side groups different thin film preparation techniques can be employed. Here we will describe shortly main techniques used in polymer thin film preparation. 

One can polymerize monolayer film on water subphase (Day and Ringsdorf (1978)) and so formed polymer monolayer can be transferred on a substrate. Polymer chains of obtained in this way thin film are parallel to the substrate (cf. Kajzar et al (I988)). The thickness of thin film can be increased by increasing the number of monomolecular polymer film transfers. 

Other technique consists on the transfer of monomer film on a substrate and its polymerization with UV or T irradiation. Again the thickness of monomer thin film depends on the number of successive transfers of monomolecular monomer layers. 

In the case of polydiacetylenes the LB technique gives polycrystalline thin films scattering strongly the light, thus not applicable for any 

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Thin-film solid electrolytes in the range of lpm have the advantage that the material which is inactive for energy storage is minimized and the resistance of the solid electrolyte film is drastically decreased for geometrical reasons. This allows the application of a large variety of solid electrolytes which exhibit quite poor ionic conductivity but high thermodynamic stability. The most important thin-film preparation methods for solid electrolytes are briefly summarized below. 

Self-assembly, in supramolecular chemistry, 24 49—50 Self-assembly thin film preparation method, 17 57-58... 

Solution Deposition of Thin Films. Chemical methods of preparation may also be used for the fabrication of ceramic thin films (qv). MetaHo-organic precursors, notably metal alkoxides (see Alkoxides, metal) and metal carboxylates, are most frequently used for film preparation by sol-gel or metallo-organic decomposition (MOD) solution deposition processes (see Sol-GEL technology). These methods involve dissolution of the precursors in a mutual solvent control of solution characteristics such as viscosity and concentration, film deposition by spin-casting or dip-coating, and heat treatment to remove volatile organic species and induce crystaHhation of the as-deposited amorphous film into the desired stmcture. 

Torimoto T, Nagakubo S, Nishizawa M, Yoneyama H (1998) Photoelectrochemical properties of size-quantized CdS thin films prepared by an electrochemical method. Langmuir 14 7077-7081... 

Castro RJ, Cabrera CR (1997) Photovoltammetry and surface analysis of MoSea thin films prepared by an intercalation-exfoliation method. J Electrochem Soc 144 3135-3140... 

An experiment has shown that thin films prepared of various materials (Co, C03O4, Ag, Ti02, ZnO) feature C>2( Aj ) sensitivity. The highest sensitivity, 2 to 3 orders of magnitude above the sensitivity of calorimetric methods, is featured by the film prepared of partially reduced zinc oxide. During interaction with such films, the 02( ) behave as... 

An example of this process of data analysis is provided by the work of Yubero et al. (2000), who studied the structure of iron oxide thin films prepared at room temperature by ion beam induced chemical vapour deposition. Such films find important applications because of their optical, magnetic, or magneto-optical properties. They were produced by bombardment of a substrate with Oj or Oj + Ar+ mixtures, and Figure 4.15 shows RBS spectra of two iron oxide thin films prepared on a Si substrate by each of these bombardment methods. 

Tanahashi I, Manabe Y, Tohda T, Sasaki S, Nakamura A (1996) Optical nonlinearities of Au/Si02 composite thin films prepared by a sputtering method. J Appl Phys 79 1244-1249... 

An overview of the precursors, process chemistry, and relative advantages and disadvantages of the three principal methods of inorganic electronic thin film preparation is shown in Table 2.1. Generally, sol-gel methods offer the greatest control over the nature of the solution precursor species, but they have involved... 

The above methods represent the most commonly employed methods for inorganic electronic thin film preparation. A variety of other methods, including Pechini,21 citrate,86 nitrate,23 and aqueous processes87 have also been used. For a discussion of these methods, the reader is referred to Refs. 5 through 12, which highlight these methods for the preparation of various electronic ceramic materials. 

After the precursor stock solution is prepared, various techniques can be used to coat the substrate, depending on the solution viscosity, required film thickness and coverage. The most common methods in the semiconductor industry are spin- and dip-coating. Other processes that are used for deposition include spray coating and stamping. A summary of the uses, limitations, and advantages of the various thin film deposition methods is reported in Table 2.2. 

Jimenez-Gonzalez, A. Nair, P. K. 1995. Photosensitive ZnO thin films prepared by the chemical deposition method SILAR. Semicond. Sci. Technol. 10 1277-1281. 

Qiu, J. Jin, Z. Wu, W. Xiao, L.-X. 2006. Characterization of CuInS2 thin films prepared by ion layer gas reaction method. Thin Solid Films 510 1-5. 

Bei Z, Ren D, Cui X, Shen J, Yang X, Zhang Z (2004) Photoelectrochemical properties and crystalline structure change of Sb-doped TiOz thin films prepared by the sol-gel method. J Mater Res 19 3189-3195... 

UV light induced refractive index change has been observed in organic polysilane (PS)-silica and PS-titania hybrid thin films prepared by the sol-gel method.135 The magnitude of the refractive index change was found to be 0.16 for 50 wt % PS-silica and 0.18 for 50 wt % PS-titania hybrid thin films. It was demonstrated that the refractive index change of the hybrid thin films is due to the photodecomposition of PS. These findings indicate potential usefulness of the hybrid thin films as optical devices with refractive index modulated structures. 

To conclude with the primary electrode characteristics, we describe briefly the DLC electrodes. The data are scarce and partly contradictory, probably due to the differences in film preparation methods. According to Howe [60], even films as thin as 50 nm are quite stable against corrosion. However, in later works [61, 62] such thin films turned permeable for electrolytes. The penetration of the electrolyte to a substrate metal resulted in its corrosion and, ultimately, in film peeling. Thicker films (0.1 to 1 pm) were less subjected to damage. The current-potential curves in supporting electrolytes resemble those for crystalline diamond electrodes (see Figs. 7, 8) the potential window is narrower, however [63], Fluorination of a-C H enhances corrosion resistance of the films significantly [64],... 

Espinos, J. P., Fernandez, A., Caballero, A., Jimenez, V. M., Sanchez-Lopez, J. C., Contreras, L., Leinen, D. and GonzalezElipe, A. R. (1997). Ion-beam-induced CVD An alternative method of thin film preparation. Chem. Vapor Deposit. 3(4), 219-226. 

Kikuchi, H., Kitano, M., Takeuchi, M., Matsuoka, M., Anpo, M. and Kamat, P. V. (2006). Extending the photoresponse of Ti02 to the visible light region Photoelectrochemical behavior of Ti02 thin films prepared by the radio frequency magnetron sputtering deposition method. J. Phys. Chem. B 110(11), 5537-5541. 

Kim, J. H., Fujita, S. and Shiratori, S. (2006). Fabrication and characterization of Ti02 thin film prepared by a layer-by-layer self-assembly method. Thin Solid Films 499(1-2), 83-89. 

Yu, J. G., Zhao, X. J. and Zhao, Q. N. (2000). Effect of surface structure on photocatalytic activity of Ti02 thin films prepared by sol-gel method. Thin Solid Films 379(1-2), 7-14. 

Zheng, S. K., Wang, T. M., Xiang, G. and Wang, C. (2001). Photocatalytic activity of nanostruc-tured Ti02 thin films prepared by dc magnetron sputtering method. Vacuum 62(4), 361-366. 

Thin-film preparation can be coupled to other synthetic strategies such as sol-gel synthesis. For example, Qide et al. presented a synthesis of Ti02 thin films prepared by the sol-gel method (Qide et al., 2003). The interest in thin films of Ti02 lies in the application of these films to photocatalysis. Ti02 has been shown to be photocatalytic with respect to the oxidation of organic contaminants such as chloroform (Fujishima et al., 1999) ... 

Yasui H. Tsuda Y. ITO thin films preparated by magnetron sputtering method using no target (effects of plasma conditions and substrate temperature on nO film properties). Nihon-Kikaigakkai-Ronbunsyu 1993 59 593-98. 

This controlled dye array can be mimicked using thin film preparation techniques. The LB method is the technique most suited to layering various dye molecules in a desired sequence and at desired distances. Figure 6.8 shows hetero-type LB films that can mimic the dye array in the photosynthetic system of a cyanobacterium. Detailed time-resolved fluorescence spectra upon... 

As shown previously, a technique for thin film preparation at low temperatures has been developed in which photoirradiation is combined with the sol-gel method. This has been used to produce Si02 thin films. Harder, denser films were prepared at lower temperatures than by conventional heat treatment. The hardness and HF etch rate were related to the molecular structure of the thin films. Photoirradiation cleaved Si-O-Si bonds so that unfolding of the Si02 ring structure was enhanced at low temperatures and densification of the thin film was promoted. 

This chapter reviews the general aspects of the CSD method for ferroelectric thin-film preparation, with attention given to precursors, solution chemistry, and process development. An additional focus of the chapter is on the structural evolution of the solution precursor into the crystalline (typically perovskite) state and the impact of precursor chemistry and film fabrication conditions on the transformation process. Lastly, the chapter reviews the advantages and disadvantages of the CSD method and discusses industrial implementation of the technique. 

We show by X-ray diffraction in the Bragg-Brentano geometry that the atomic stmcture of lead sulfide nanoparticles in thin films prepared by wet chemical method is different from the B stmcture, which is the equilibrium phase for bulk single-crystalline PbS. The atomic structure of nanoparticles can be desaibed by the cubic space group Fm-3m with both tetrahedral and octahedral coordinations for sulfur atoms. 

Tamaki, J. Shimanoe, K Yamada, Y. Yamamoto, Y. Miura, N. Yamazoe, N., Dilute hydrogen sulfide sensing properties of CuO-Sn02 thin film prepared by low-pressure evaporation method, Sens. Actuators B 1998, 49, 121-125... 

Liposomes are mostly prepared by the thin film hydration method in which a thin fihn is produced by dissolving the phospholipids in suitable organic solvent... 

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