Substrate coverage

Since the diameters of both kinds of particles are about 200 mn, the thickness of a 10-layer assembly should be about 1.8 p,m. However, the cross section of a sample subjected to 10-fold dipping indicates a thickness of only 1.2 jim (Fig. 21). Similar observations were made by others [94,97] and can be ascribed to the low substrate coverage reached in each of the dipping steps. Serizawa et al. [97] used the second approach and determined the adsorption using QCM and SEM. An SEM image after two adsorption steps indicated a very irregular, amorphous structure, in agreement with Fulda and coworkers [93]. 

Thin films have also been cast from fluorocarbon-surfactant-containing SUVs with bound poly(vinyl alcohol) [436, 437]. Wide angle X-ray diffraction measurements have been interpreted in terms of highly oriented multibilayers and complete substrate coverage by the fluorocarbon surfactants, even at low surfactant-to-poly(vinyl alcohol) ratios (Fig. 70) [437]. 

Conditions for Uniform Substrate Coverage. Foam delivered in the FFT Process to a fabric substrate at a given add-on rate (per cent by weight) requires a certain time to break and absorb into the fabric. The rate of adsorption will depend on the foam ccnposition and properties, and on the composition, structure and sorbancy of the fabric substrate under the conditions of application. For a given foam and fabric combination, the time... 

By considering that both substrate and oxygen must be present in the system for the occurrence of photoreaction, it is assumed that the total disappearance rate of substrate per unit surface area, rx, follows a second-order kinetics of first order with respect to the substrate coverage and of first order with respect to the oxygen coverage ... 

Diamond nucleation rates on foreign substrates decrease as the substrate coverage with diamond and the crystal size increase. 

A number of important factors must be considered when studying TOF-SIMS of polymers. Included are the nature of the substrate, substrate coverage, substrate pretreatment, the primary ion, polymer molecular weight, and the solvent used in sample preparation. 

Alkali Substrate Coverage range Angle range [deg] Ref... 

Up position as a function of the substrate coverage, was observed together with a charge transfer occurring from the porphyrin macrocycle to the fullerene species accompanied by a diffusion of the Ceo spheres throughout the ZnPf layers (see Fig. 4.13). 

Fig. 24. Substrate coverage versus time dependence for exactly solvable model (Osipov 1990).

Four common examples of substrate coverage on an fee strueture. The surfaee metal atoms are represented by shaded circles and the absorbate by white circles. The heavy line outlines the new unit cell for each example. 

Current and anticipated uses of organic thin films include those that may be classed as "passive", such as for electrical insulation or protection against corrosion, and others in which the films "actively" contribute to an electrical or optical response. The effectiveness of these films depends upon achieving dense substrate coverage with layers of defined thicknesses of tens to hundreds of angstroms. Many of the latter, "active," applications rely additionally upon the spacing and directional sequence or orientation of multiple chemical components comprising the film. 

Vacuum deposition is the most energy-efficient of the PVD processes. Where the substrate coverage, adhesion, process throughput, and film properties are acceptable, it is generally the PVD process of choice. 

---