Films on solids

In the case of Langmuir monolayers, film thickness and index of refraction have not been given much attention. While several groups have measured A versus a, [143-145], calculations by Knoll and co-workers [146] call into question the ability of ellipsometry to unambiguously determine thickness and refractive index of a Langmuir monolayer. A small error in the chosen index of refraction produces a large error in thickness. A new microscopic imaging technique described in section IV-3E uses ellipsometric contrast but does not require absolute determination of thickness and refractive index. Ellipsometry is routinely used to successfully characterize thin films on solid supports as described in Sections X-7, XI-2, and XV-7. 

Equations X-12 and X-13 thus provide a thermodynamic evaluation of the change in interfacial free energy accompanying adsorption. As discussed further in Section X-5C, typical values of v for adsorbed films on solids range up to 100 ergs/cm. ... 

Sun F, Castner D G and Grainger D W Ultrathin 1993 Self-assembled polymeric films on solid-surfaces. 2. Formation of 11-(n-pentyldithio)undecanoate-bearing polyacrylate monolayers on gold Langmuirs 3200-7... 

J. G. Dash. Films on Solid Surfaces. New York Academic Press, 1974. 

Major structural Felted fiber with High-porosity film on Solid urethane sheet with filer Solid polymer sheet... 

In order to study the structure of Langmuir films of polymers spheres, most researchers deposited the films on solid substrates using the LB technique [158-162] and analyzed the structure using a microscope. A modified version of the LB method allowing the transfer of particle monolayers is outlined in Figure 8a. 

Previously, we recorded UV absorption spectra of the same molecules in spread monolayers on the water surface and in 11-monolayer LB films on solid substrates as shown in Figure 11 [11]. In the case of C8AzoC5, the absorption band due to the it-it transition of the azobenzene moiety in the spread monolayer is largely shifted to... 

Cook, M. A. and Nixon, J. C., 1950. Theory of water-repellent films on solids formed by adsorption fi-om aqueous solutions of heteropolar compounds. J. Phys. Colloid Chem., 54 445 - 459... 

The growth of thin films on solid surfaces is important in technology, and nucleation is one of the keys for understanding the growth mechanism. The ability of STM to image local structures down to atomic detail makes it ideal for the study of nucleation, thin film growth, and crystal growth. 

A fundamental equation derived by Gibbs is used to calculate the spreading pressure of films on solids where, unlike films on liquids, it cannot be experimentally determined. Guggenheim and Adam reduced Gibbs general adsorption equation to equation (7.3) for the special case of gas adsorption... 

The state of the adsorbed film on solids could be elucidated most simply from entropy data. If the entire entropy change can be attributed to the adsorbate. Jura and Hill (17) showed that the difference in entropy of the adsorbed film Sa and the entropy of the bulk liquid Si, is given by the expression... 

Equation (6.25) not only allows us to calculate the Hamaker constant, it also allows us to easily predict whether we can expect attraction or repulsion. An attractive van der Waals force corresponds to a positive sign of the Hamaker constant, repulsion corresponds to a negative Hamaker constant. Van der Waals forces between similar materials are always attractive. This can easily be deduced from the last equation for 1 = e2 and n = n2 the Hamaker constant is positive, which corresponds to an attractive force. If two different media interact across vacuum ( 3 = n3 = 1), or practically a gas, the van der Waals force is also attractive. Van der Waals forces between different materials across a condensed phase can be repulsive. Repulsive van der Waals forces occur, when medium 3 is more strongly attracted to medium 1 than medium 2. Repulsive forces were, for instance, measured for the interaction of silicon nitride with silicon oxide in diiodomethane [121]. Repulsive van der Waals forces can also occur across thin films on solid surfaces. In the case of thin liquid films on solid surfaces there is often a repulsive van der Waals force between the solid-liquid and the liquid-gas interface [122],... 

In many applications, films on solid surfaces are only metastable or they are stable only from a certain thickness. Example are metal films prepared by evaporation [291] and many polymer films. Since most paints and coatings contain a substantial amount of polymer, this is a highly relevant case. 

Figure 7.19 Dip and spin coating are two common techniques to form polymer films on solid surfaces.

It has been recognized for many years that films on solid surfaces can influence the mechanical behavior of a solid. Mechanical activation gives rise to the input of a considerable quantity of energy at the surface. This energy can produce a number of changes in the nature of the solid surfaces and the lubricant additives that interact with the solid surface to provide a very stable surface tribofilm (see Table 5.6)... 

The solid films on the air-water interface, while fundamentally interesting, do not seem to have any obvious potential practical applications. On the other hand, the importance of organic films on solid substrates cannot be overestimated. Apart from applications in electronics, optics, protective coatings, etc., organized organic thin films are an excellent model system for... 

Dash J.G. (1975) Films on Solid Surfaces, Academic Press, New York. 

Conner W C (1997) In Physical Adsorption Experiment, Theory and Applications (J Fraissard and W C Conner, eds), Kluwer, Dordrecht, p 33 Costa E, Calleja G and Manjuan L (1988) Adsorption Sci Techn 5,213 Dacey J R, Clunie J C and Thomas D G (1958) Trans Faraday Soc 54,250 DashJG (1975) Films on Solid Surfaces, Academic Press, New York, p 53 Davis BW and Pierce C (1966)/ Phys Chem 70,1051... 

CFD [Chemical Fluid Deposition] A process for depositing thin films on solid surfaces by a chemical reaction in a liquid such as supercritical carbon dioxide. Superior to CVD in being capable of operation at almost ambient temperatures. Demonstrated for depositing platinum metal on silicon wafers, polymer substrates, and porous solids by hydrogen reduction of an organo-platinum compound at 80°C. 

In the oil flotation process emulsion drops to which ore particles adhere are used instead of gas bubbles. In the case of film flotation the crushed ore is dumped on a continuously moving water surface. The easily wetted particles sink while the poorly wettable ones remain at the surface and are then collected with a special device. The theory of particle extraction by flotation have been further developed due to the detailed study of the elementary stages of particle adhesion and attachment to bubbles, accounting for the interaction forces of wetting films on solid substrate [e.g. 15-17]. 

TABLE 4 Spreading Pressure (in I0 3 N/m) of Adsorbed Films on Solids Measured by Adsorption Experiments... 

Analogous to the supramolecular TRPyP systems, the tetramthenated porphyr-azine species also form homogeneous molecular films on solid substrates, by the slow evaporation of the solvent. Such films are suitable for the preparation of modified electrodes displaying versatile electrochemical and photoelectrochem-ical properties. The spectrum of a TRPyPz film on ITO is analogous to the solution spectrum exhibiting the Soret band at 390 and a broad Q band at 705 nm, respectively and the peripheral ruthenium complexes n-n and CT bands at 300 and 500 nm (125, 126). 

Numerous authors have more recently expanded the expression for the cross section given by equation (32) in various ways. Most of this work is for determining the structure of adsorbed films on solid substrates in particular graphite. The details of these expansions can be found in Stephens etal.J Dutta etal and Dimon etal. The work of Dimon et al. is particularly noteworthy in that it finds that a Lorentzian distribution gives a more satisfactory fit to the lineshape. Our recent experimental evidence suggests that the... 

The deposition of molecular films on solid substrates was initially of the Lang-muir-Blodgett type [186, 187], where layers preformed on a liquid-air interface are carefully transferred on to a solid surface. The difficulties associated with deposition of LB films are overcome in systems where molecules from a solution phase assemble themselves on a solid surface in the form of a one molecule thick film. If the interaction between the head groups of the molecules with the substrate surface is of the covalent type, as in the case of surface silanization [188, 189], then we can expect the film to be mechanically robust. 

Another example of phase change during reaction is chemical vapor deposition (CVD), a process used to manufacture microelectronic materials. Here, gas-phase reactants are deposited (analogous to condensation) as thin films on solid surfaces (see Problem P3-25). One such reaction is the production of gallium arsenide, which is used in computer chips. 

Schonhoff, M., Chi, L. F., Fuchs, H, and Losche, M. Structural Rearrangements Upon Photoorientation of Amphiphilic Azobenzene Dyes Organized in Ultrathin Films on. Solid Surfaces. Langmuir 11, 163 (1995). 

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