Thin-film chemistry

Fig. 2.12 Schematic diagram of the Eastman Kodak slide for solid-phase or thin-film chemistry, illustrating the chemistry integrated into the multilayers.

One major reason for the great interest in the processes of thin metal-containing films is that reactions on the surface of small metal clusters can be studied. Indeed, prior to the development of thin-film chemistry, reactions of similar particles were studied only in the gas phase at rather high temperatures. Under these conditions, most of the primary products are unstable and decompose in the course of further reaction, which is non-selective. As a result, the information obtained on the routes and mechanisms of reactions of disperse metals appears to be scarce, while the use of such reactions in synthesis is inexpedient. Conversely, low-temperature reactions in the films of co-condensates are very promising from the standpoint of determining the detailed reaction mechanism, as well as for synthesis of previously unknown complexes and organometallic compounds. It is important that atoms of only a few metals react with organic compounds immediately at the instant of their contact on the cooled substrate. Rather often, atoms and/or small (molecular) clusters are first stabilized in the film, and then their transformations are observed. 

Miyauchi, M., A.K. Nakajima, T. Watanabe and K. Hashimoto (2002). Photoinduced hydrophilic conversion of Ti02/W03 layered thin films. Chemistry of Materials, 14(11), 4714 1720. 

Veith, M., Mathur, S., Shen, H., Lecerf, N., Huefner, S., and Jilavi, M.H. (2001) Single-step preparation of oxide-oxide nanocomposites chemical vapor synthesis of LnAlOs/ALOs (Ln = Pr Nd) thin films. Chemistry of Materials, 13, 4041-4052. 

Huang, M. H. Soyez, H. M. Dunn, B. S. Zink, J. I., In situ fluorescence probing of molecular mobility and chemical changes during formation of dip-coated Sol-gel silica thin films. Chemistry of Materials 2000, 12(1), 231-235... 

M. Ritala, M. Leskela, L. Niinisto, P. Haussalo, Titanium isopropoxide as a precursor in atomic layer epitaxy of titanium dioxide thin films . Chemistry of Materials, 5,1174-1181, (1993). 

Cerasimova, T.N., Orlova, N. A., Shelkovnikov, V.V., Ivanova, Z. M, Markov, R. V., Plekhanov, A,L, Polyanskaya, T. M, Volkov, V. V. (2000). The Structure of Pseudoisocyanine Decahydro-cZoso-decaborate and Its Nonlinear Optical Properties in Thin Films. Chemistry for Sustainable Development. Vol.8, pp.109-114. 

Yuan, P., et al. UV pattemable thin film chemistry for shape and functionally versatile self-oscillating gels. Soft Matter 9(4), 1231-1243 (2013)... 

Experimental confirmation of the theory of electron transfer with polymer films, and the ramifications of this new knowledge demonstrate that there is a tremendous opportunity to control interfa-cial electron transfer via surface and thin-film chemistry. The ideal, polarizable electrode, once an icon for electroanalytical chemists, now serves as a hypothetical support for molecular-scale organized assemblies that carry out the business of controlled electron transfer. Examples of early prototype assemblies are given below. 

Bardo, A. M., M. M. Collinson and D. A. Higgins (2001). "Nanoscale properties and matrix-dopant interactions in dye-doped organically modified silicate thin films." Chemistry of Materials 13(8) 2713-2721. 

Tertiary bismuthines appear to have a number of uses in synthetic organic chemistry (32), eg, they promote the formation of 1,1,2-trisubstituted cyclopropanes by the iateraction of electron-deficient olefins and dialkyl dibromomalonates (100). They have also been employed for the preparation of thin films (qv) of superconducting bismuth strontium calcium copper oxide (101), as cocatalysts for the polymerization of alkynes (102), as inhibitors of the flammabihty of epoxy resins (103), and for a number of other industrial purposes. 

PZN-PT, and YBa2Cug02 g. For the preparation of PZT thin films, the most frequently used precursors have been lead acetate and 2irconium and titanium alkoxides, especially the propoxides. Short-chain alcohols, such as methanol and propanol, have been used most often as solvents, although there have been several successful investigations of the preparation of PZT films from the methoxyethanol solvent system. The use of acetic acid as a solvent and chemical modifier has also been reported. Whereas PZT thin films with exceUent ferroelectric properties have been prepared by sol-gel deposition, there has been relatively Httle effort directed toward understanding solution chemistry effects on thin-film properties. 

Two capabilities of ISS are important in applications to the analysis of ceramics. One of these is its surface sensitivity. Many catalyst systems use ceramics where the surface chemistry of the outer 50 A or less is extremely important to performance. Comparing the ratio of H and O to AI or Si is equally important for many systems involving bonding operations, such as ceramic detectors, thin films, and hydroxyapatite for medical purposes. 

Obtaining the aqueous solution to analyze is often a challenge in materials analysis. Thin films usually can be dissolved by acids without dissolving the underlying substrate, however sometimes this is difficult. A film can also be oxidized and the oxide dissolved. Temperatures involved in this procedure are sometimes quite elevated so care must be taken to maintain sample integrity. The chemistry of the sample must be kept in mind so that the limits of the analysis are known. 

Therefore, this book is to give the analyst - whether a newcomer wishing to acquaint themself with new methods or a materials analyst needing to inform themself on methods that are not available in their own laboratory - a clue about the principles, instrumentation, and applications of the methods, techniques, and procedures of surface and thin-film analysis. The first step into this direction was the chapter Surface and Thin Film Analysis of Ullmann s Encyclopedia of Industrial Chemistry (Vol. B6, Wiley-VCH, Weinheim 2002) in which practitioners give briefly outline the methods. 

At the start of this Chapter, an essay by Peter Day was quoted in which he lauds the use of soft chemistry , exemplifying this by citing the use of organometallic precursors for making thin films of various materials used in microelectronics. The same approach, but without the softness, is increasingly used to make ceramic fibres here, ceramic includes carbon (sometimes regarded as almost an independent state of matter because it is found in so many forms). 

It can be shown, (Gibbs, Scientific Papers, I. J. J. Thomson, Applications of Dynamics to Physics and Chemistry), that a chemical equilibrium can be modified by the action of capillary forces. Thus, a state of equilibrium in solution may conceivably be modified if the latter is in the form of thin films, such as soap bubbles. Since, according to Freundlich (Kapillarchemie, 116), there is at present no direct evidence of the existence of such modification (which would no doubt be exceedingly, though possibly measurably, small) we shall not enter any further into the matter here. 

Chen ZM, Zabik MJ, Eeavitt RA. 1984. Comparative study of thin film photodegradation rates for 36 pesticides. Industrial and Engineering Chemistry Product Research and Development 23 5-11. 

XPS is among the most frequently used techniques in catalysis. It yields information on the elemental composition, the oxidation state of the elements and, in favorable cases, on the dispersion of one phase over another [ J.W. Niemantsverdriet, Spectroscopy in Catalysis, An Introduction (2000), Wiley-VCH, Weinheim G. Ertl and J. Kiippers, Low Energy Electrons and Surface Chemistry (1985), VCH, Weinheim L.C. Feldman and J.W. Mayer, Fundamentals of Surface and Thin Film Analysis (1986), North-Holland, Amsterdam]. 

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