Layer growth

One drawback of static crystallization is that crystal layer growth rates are very slow. In the Sulzer MWB process, growth rates are gready improved by allowing a film to dow down vertical tubes (83). 

Internal Flow. Depending on the atomizer type and operating conditions, the internal fluid flow can involve compHcated phenomena such as flow separation, boundary layer growth, cavitation, turbulence, vortex formation, and two-phase flow. The internal flow regime is often considered one of the most important stages of Hquid a tomiza tion because it determines the initial Hquid disturbances and conditions that affect the subsequent Hquid breakup and droplet dispersion. 

Blade loading or diffusion loss. This loss is due to the type of loading in an impeller. The inerease in momentum loss eomes from the rapid inerease in boundary-layer growth when the veloeity elose to the wall is redueed. This loss varies from around 7% at a high-flow setting to about 12% at a low-flow setting. 

Friction loss The pressure energy loss that takes place in duct or pipe flow. It is related to the Reynolds number, boundary layer growth, and the velocity distribution. 

More recently, simulation studies focused on surface melting [198] and on the molecular-scale growth kinetics and its anisotropy at ice-water interfaces [199-204]. Essmann and Geiger [202] compared the simulated structure of vapor-deposited amorphous ice with neutron scattering data and found that the simulated structure is between the structures of high and low density amorphous ice. Nada and Furukawa [204] observed different growth mechanisms for different surfaces, namely layer-by-layer growth kinetics for the basal face and what the authors call a collected-molecule process for the prismatic system. 

As an example of a multilayer system we reproduce, in Fig. 3, experimental TPD spectra of Cs/Ru(0001) [34,35] and theoretical spectra [36] calculated from Eq. (4) with 6, T) calculated by the transfer matrix method with M = 6 on a hexagonal lattice. In the lattice gas Hamiltonian we have short-ranged repulsions in the first layer to reproduce the (V X a/3) and p 2 x 2) structures in addition to a long-ranged mean field repulsion. Second and third layers have attractive interactions to account for condensation in layer-by-layer growth. The calculations not only successfully account for the gross features of the TPD spectra but also explain a subtle feature of delayed desorption between third and second layers. As well, the lattice gas parameters obtained by this fit reproduce the bulk sublimation energy of cesium in the third layer. 

In the process of MBE, the surface structure can be investigated by reflected high energy electron diffraction (RHEED). During MBE growth, one often observes an oscillation in the intensity of the specular reflected beam as a function of time. This is interpreted to be due to the layer-by-layer growth of a two-dimensional island. 

The study of ultra-thin Fe thin films on Cu(OOl) substrate has attracted a lot of interest in the past. This is due to the abundance of interesting phenomena associated with this system. Due to the small epitaxial misfit a good layer by layer growth is expected stabilizing the film in a structure related to the fee phase of bulk Fe which is otherwise unstable at low temperatures It also become a test system for magnetic measurements. 

Mass transport measurements have shown that cation transport predominates in FeO (Fe ) and Fej04 (Fe, Fe ), whereas anion transport predominates in FejOj (0 ). This leads to the well-accepted growth scheme for multi-layered scale growth on iron shown in Fig. 7.3, with the governing equations for individual layer growth being ... 

For many low alloy steels, therefore, the scale phase sequence is as shown in Fig. 7.5 and the governing equations for individual layer growth are similar to those for pure iron, with the addition of ... 

Lewis, C. R., MOCVD Adds Consitency toIH-V Semiconductor Thin-layer Growth, i c5. c Z)ev., pp. 106-110 (Nov. 1985)... 

Figure 1 shows AES data for the oxidized titanium surface before and after deposition of 30 X of platinum with the substrate held at 130 K. The platinum thickness was calculated from the attenuation of the oxygen AES signal assuming layered growth of the metal. From the spectra It Is clear that the platinum was sufficient to completely attenuate the underlaying features of the titanium oxide. 

After formation of a primary deposit layer on foreign substrates, further layer growth will follow the laws of metal deposition on the metal itself. But when the current is interrapted even briefly, the surface of the metal already deposited will become passivated, and when the current is turned back on, difficulties will again arise in the formation of first nuclei, exactly as at the start of deposition on a foreign substrate (see Section 14.5.3). This passivation is caused by the adsorption of organic additives or contaminants from the solution. Careful prepurification of the solution can prolong the delay with which this passivation will develop. 

Regen and Watanabe [158] fabricated multi-layers close to a thickness of 800 A by using fourth or sixth generation PAM AM dendrimers with 16 or 12 cycles, respectively. The construction techniques involved activation with K2PtCl4 on a silicon wafer containing amino groups on the surface, which was followed by deposition of the dendrimer layer. However, elimination of Pt2+ layer resulted in absence of layer growth, as examined by X-ray photoelectron spectroscopy. 

A natural progression from using CA to model bacterial growth is to model tumor growth and the development of abnormal cells. There has been considerable work on this topic. Features such as cell mutation, adhesion, layered growth, and chemotaxis can readily be incorporated into a CA model.5 Deutsch and Dormann s book provides a useful introduction to this area.6... 

EC-ALE is the combination of UPD and ALE. Atomic layers of a compound s component elements are deposited at underpotentials in a cycle, to directly form a compound. It is generally a more complex procedure than most of the compound electrodeposition methods described in section 2.4.2, requiring a cycle to form each monolayer of the compound. However, it is layer-by-layer growth, avoiding 3-D nucleation, and offering increased degrees of freedom, atomic level control, and promoting of epitaxy. 

T. F. Kuech, P. D. Dapkus, and Y. Aoyagi, Atomic Layer Growth and Processing, Vol. 222, Materials Research Society, Pittsburgh, 1991. 

---