Solution-derived thin films

Dobberstein, H. Schwartz, R. W. 2002. Modeling the nucleation and growth behavior of solution derived thin films. Proc. 1st Symp. Adv. Mat. Next Generation—Prelude to Func.-Int. Mat. (AIST Chubu, Nagoya, Japan). 

Dobberstein, H. 2002. A thermodynamic and kinetic model for nucleation and growth in solution derived thin films. PhD dissertation. Clemson University, Clemson, SC. 

Polyaniline (PANI) can be formed by electrochemical oxidation of aniline in aqueous acid, or by polymerization of aniline using an aqueous solution of ammonium thiosulfate and hydrochloric acid. This polymer is finding increasing use as a "transparent electrode" in semiconducting devices. To improve processibiHty, a large number of substituted polyanilines have been prepared. The sulfonated form of PANI is water soluble, and can be prepared by treatment of PANI with fuming sulfuric acid (31). A variety of other soluble substituted AJ-alkylsulfonic acid self-doped derivatives have been synthesized that possess moderate conductivity and allow facile preparation of spincoated thin films (32). 

Barium titanate thin films can be deposited on various substances by treating with an aqueous solution containing barium salts and an alkanolamine-modifted titanate such as TYZOR TE (151). In a similar fashion, reaction of a tetraalkyl titanate with an alkah metal hydroxide, such as potassium hydroxide, gives oxyalkoxide derivatives (KTi O(OR) ), which can be further processed to give alkali metal titanate powders, films, and fibers (152—155). The fibers can be used as adsorbents for radioactive metals such as cesium, strontium, and uranium (156). 

One of the more important uses of OM is the study of crystallization growth rates. K. Cermak constructed an interference microscope with which measurements can be taken to 50° (Ref 31). This app allows for study of the decompn of the solution concentrated in close proximity to the growing crystal of material such as Amm nitrate or K chlorate. In connection with this technique, Stein and Powers (Ref 30) derived equations for growth rate data which allow for correct prediction of the effects of surface nucleation, surface truncation in thin films, and truncation by neighboring spherulites... 

Figure 13.5 Potential-step electro-oxidation of formic acid on a Pt/Vulcan thin-film electrode (7 p,gptcm, geometric area 0.28 cm ) in 0.5 M H2SO4 solution containing 0.1 M HCOOH upon stepping the potential from 0.16 to 0.6 V (electrol)Te flow rate 5 p,L s at room temperature). (a) Solid line, faradaic current transients dashed line, partial current for HCOOH oxidation to CO2. (b) Solid line, m/z = 44 ion current transients gray line, potential-step oxidation of pre-adsorbed CO derived upon HCOOH adsorption at 0.16 V, in HCOOH-ftee H2SO4 solution.

Order and polydispersity are key parameters that characterize many self-assembled systems. However, accurate measurement of particle sizes in concentrated solution-phase systems, and determination of crystallinity for thin-film systems, remain problematic. While inverse methods such as scattering and diffraction provide measures of these properties, often the physical information derived from such data is ambiguous and model dependent. Hence development of improved theory and data analysis methods for extracting real-space information from inverse methods is a priority. 

Kato, K. Zheng, C. Dey, S. K. Torii, Y. 1997. Chemistry of the alkoxy-derived precursor solutions for layer-structured perovskite thin films. Int. Ferro. 18(l-4) 225-235. 

Voigt, J. A. Tuttle, B. A. Headley, T. J. Lamppa, D. L. 1995. The pyrochlore-to-perovskite transformation in solution-derived lead zirconate titanate thin films. In Ferroelectric Thin Films IV, edited by Tuttle, B. A. Desu, S. B. Ramesh, R. Shiosaki,T. Mat. Res. Soc. Symp. Proc. 361 395 102. 

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