Deposition rate normalized

While deposition rate normally increases with increase in pH for the standard bath, using an ammonium salt to lower the solution pH resulted in the opposite behavior i.e., increased pH led to slower deposition [22]. The pH in these experiments was increased by adding NH4OH. Increased pH (and NH4OH) results in two opposing effects Thiourea decomposition increases but free [Cd ] decreases. Since the deposition rate for the solution with no added NHj increases with increase in pH, the former apparently outweighs the latter. When extra ammonium ion is added, much more ammonium hydroxide is needed to increase the... 

The essential constituent of the bath is sodium tetrachromate, Na2Cr40,3, which is, however, only stable at temperatures below about 25°C. This temperature should therefore not be exceeded in the operation of the bath. Current densities of 75-150 A/dm are used. The current efficiency of the bath is high (30-35%) so that the metal is deposited at the rate of about 1 tm/min. The deposits are normally matt in appearance, but are comparatively soft and readily polished. 

Figure 16.6 TEM micrographs of titania-supported Au particles. The nominal thickness of An was (a) 0.13 nm (h) 0.78nm (c) 1.56nm (d) 2.33 nm. The Au deposition rate was 2.6 X 10 nms. Particle size distributions of Au for various deposition times are shown in the plot, with the distrihutions fitted to a normal Gaussian function.

In the ASTER reactor deposition experiments were performed in order to compare with the 2D model results. Normalized deposition rates are plotted in Figure 22 as a function of radial position for data taken at 25 and 18 Pa. The deposition takes place on a square glass plate. For each pressure two profile measurements were performed, each profile perpendicular to the other (a and b in Fig. 22). A clear discrepancy is present. The use of the simplified deposition model is an explanation for this. Another recent 2D fluid model also shows discrepancies between the measured and calculated deposition rate [257], which are attributed to the relative simplicity of the deposition model. 

FIG. 22. Normalized deposition rate at the grounded electrode of the 2D model compared with experiments. Discharge settings for the model are a total pressure of 20 Pa. a power of 5 W, and an RF frequency of 50 MHz. The experiments were performed al 18 and 25 Pa. The measurements were done for two perpendicular directions, a and b. (From G. J. Nienhuis. Ph.D. Thesis, Universiteit Utrecht, Utrecht, the Netherlands, 1998. with permission.)... 

Because additives are normally present in low concentration, this parameter is much larger for additives than for the metal ion. Hence, while ionic transport does not place an important limit on deposition rate inside sub-micron trenches, additive diffusion does. Both scale with L2/b so that as L is reduced at constant L/D, D becomes smaller, and additive diffusion becomes less controlling. 

Silver items, however, are also relatively rare in the archaeological record. The most common metal found is either copper, usually alloyed with either tin (bronze) or, in the later periods, zinc (brass), or iron. The latter contains very little lead and, because of severe corrosion problems, its survival rate is often low (but see Degryse et al., 2007). Fortunately, copper can also be characterized from its lead isotope signature, since the primary ore of copper is chalcopyrite (CuFeS2), which often co-occurs with galena (PbS) and sphalerite (ZnS). Even if the ore used is a secondary mineral formed by the oxidation of the primary deposit, the copper smelted from such a deposit would normally be expected to... 

For regions in which the flow is not quasisteady, a transient-flow solution may be possible. For example, Lakin and Lakin and Fox developed a two-dimensional transient-flow solution for an idealized symmetric bifurcation during the period at the end of inspiration and before expiration. Their finding that vortidty decreases at the carina or bifurcation apex suggests that particle- and gas-deposition rates may be increased at these sites in the respiratory tract. It also suggests that reactive-gas deposition rates during normal oscUlatory breathing differ... 

Figure 3. Deposition rates (D) for organo-silicones, normalized to flow rate (F) and monomer molecular weight (M), as function of plasma power (P). Shaded develope 13.56 MH plasmas data points are for 2.45 (M plasmas at monomer pressure 0.1 Torr (A) 0.2...

From the study of Kainthla et al. [48], XRD of the films showed clearly that solid solution formation occurred the (predominantly sphalerite) diffraction peaks shifted with change in composition. For compositions with S concentration < 60%, only zincblende structure formed the amount of wurtzite increased with increasing S content but was always low. The concentration of S in the films was somewhat greater than that in the deposition solution i.e., S deposited preferentially. This is not surprising since CdS deposition is normally faster than that of CdSe. The concentration of ammonia was increased as the thiourea selenosulphate ratio increased, ostensibly to slow down the rate of formation of CdS through decreased Cd concentration (although the rate of CdSe formation is also dependent on this same factor). 

For simple materials such as zinc or CaC03, research has shown stoichiometry between deposited sulfur and the base material (30). Thus in equivalent molar units, the deposition rate of sulfur is equal to the removal rate of the base material. At present environmental conditions in the U.S., these rates are low in terms of expected lifetimes of consumer-oriented components. There are some exceptions, such as galvanized fence wire, for which S02 deposition rates may be 2-3 times higher than on large flat surfaces (31). For CaC03, dissolution in (normal) rain can be an important mode of material loss and acts to remove the more soluble CaS0A, creating conditions more receptive to additional S02 deposition (32). 

The problem of assuring uniform depositions on many wafers closely spaced in a long uniform tube was solved when operation of the reactor at low pressure was considered.22 Normally, in an atmospheric pressure cold wall CVD system, the reactant gas is heavily diluted in N2 in order to reduce gas phase nucleation. At the pressures used for low pressure CVD (0.5-1.0 Torr), this is less of a problem so less diluent is needed. The net effect then is that deposition rates only fall by a factor of five. However, as many as 100 wafers can be processed in such a reactor at one time (see Figure 26), and this more than compensates for the lower deposition rate. In addition, due to the low pressure, diffusion occurs at high rates and the deposition tends to be controlled by the surface temperature. Given the very uniform temperatures available in a diffusion furnace, the deposition uniformity tends to be excellent in such a system. 

Sputtering Normal sputtering (see Section 4.2.1) is a well established technology characterized by low deposition rates (typically or order 0.1 /unh-1). 

Fig. 4.29. Normalized integrated intensities (left) of substrate core levels in dependence on deposition time for the spectra shown in Fig. 4.26. The deposition rate is estimated to be 2nmmin 1. The lines in the left graph are obtained by curve fitting of the data to an exponential decay. The derived attenuation times are displayed in the right graph in dependence on electron kinetic energy together with theoretical energy-dependent escape depth calculated using the formula by Tanuma, Powell, and Penn [37] and using a y/ E law [38]...

Lewis and Stevens mathematical treatment is fairly general, as it allows the conversion rate and deposition velocities to vary with time, as expected. For example, the rate of SO2 conversion is probably higher during daytime than at night. The value of their formulation is that the dispersion of both SO2 and SO4 and the deposition of SO4 are handled by normalization to the concentration of fine primary particles from the SO2 source. They made various assumptions about the time dependence of conversion and deposition rates and concluded that the errors are only about 10% or less if one assumes that the rates are equal to the time-averaged values. 

The measured deposition rates were normalized to the ambient concentrations of total aerosol loading to calculate deposition velocities. Calculations were made using total and fogwater loadings. We use notations ... 

To solve generally for the optimum conditions and to plot resulting deposition rates, it is useful to rewrite the pressure, temperature, density and deposition rate in terms of normalized variables. For this purpose, the normalized values are defined as p = p/p, T = T/T, and p = p/p, . Similarly, the normalized deposition rate and molecular speed are S = S/S and, 15 t5/i5 . The reference temperature, density and speed for a first-order deposition reaction are taken as... 

Now taking S = b pjjt)jj//4 as the reference deposition rate, the normalized deposition rate may be written as... 

A second useful normalization of the deposition rate is the simple modification of S given by S = Note that the normalized centerline deposition rate can be obtained from Eqs.22a, b simply by taking/ =f where/ is the normalized reactant fraction at z = 0. The pressure, temperature and all other variables in these expressions are uniform over the preform thickness. 

Thus, because, [3 and v / are the only parameters in Eqs. 10 and 11, the normalized deposition rate at the preform center is uniquely determined by the normalized pressure, temperature, preform thickness and reaction yield. 

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