Volume deposition rate

The key determinants of future cost competitiveness of a-Si H PV technology are a-Si H deposition rates, module production yields, stabilized module efficiencies, production volume, and module design. Reported a-Si H deposition rates vary by more than a factor of 10, but most researchers report that the high quaUty films necessary for high stabilized efficiencies require low deposition rates often due to high hydrogen dhution of the Si (and Ge) source gases (see Semiconductors, amorphous). 

Fig. 6. Spatial distribution of net osmoticum deposition rate per mm of tissue water in the apical 10 mm of maize primary roots growing at various vemiculite water contents (see Fig. 3). The data were obtained by dividing rates per mm length (Fig. 5) by the volume of water in each segment. The inset shows root diameter as a function of distance from the apex in the different treatments. Points are means s.d. ( = 5-6). Modified from Sharp et al. (1988, 1989).

Essentially equivalent information can be obtained during the formation of the filter cake, without the need for a second filtration. During filtration, particles are deposited as a layer of increasing thickness, so that the resistance to filtration increases. The resistance, R(m-1), is inversely related to permeability and is defined in terms of the volume flow rate ... 

For solids run-off it is assumed that this run-off water contains 200 parts per million by volume of solids thus the corresponding velocity term U12 is 200 x 10 6t Jn, i.e., 10 s m/h. This corresponds to the loss of soil at a rate of about 0.1 mm per year. If these solids were completely deposited in the aquatic environment (which is about l/10th the soil area), they would accumulate at about 0.1 cm per year, which is about a factor of four less than the deposition rate to sediments. The implication is that most of this deposition is of naturally generated organic carbon and from sources such as bank erosion. 

In order to control the condnctivity type and carrier concentration of the epitaxial layers, dopants are added to the reactant gases (cf. Section 6.1.1.5). Dopants are typically introduced in the form of hydrides (e.g., B2H6, PH3, and AsHs) in low concentrations (10-1000 ppm). There are no simple mles to relate the incorporation of dopant atoms from the gas phase into the Si film, since the incorporation depends on many factors, including snbstrate temperatnre, deposition rate, dopant molar volume, and reactor geometry. Thus, the dopanl/Si ratio in the film is different from that in the... 

Solutions of the mass balances with appropriate constitutive rate expressions for r(i, j), r(r, j), r(e, j), and r(rxt, j) for all components within the control volume yield the deposition rate and composition of the film. 

The growth kinetics describes the nucleation processes on the atomic scale. Thermally activated processes as adsorption, desorption, and diffusion at the surface and in the volume, nucleation, and crystallization/ recrystallization determine the film structure and can be controlled by the substrate temperature and the growth rate. Using a diagram ln(J ) over 1/ T, R being the deposition rate and T the growth temperature, three different growth modes (epitaxial, polycrystalline, and amorphous) can be... 

While chemical composition is important in determining the toxicity of particles and fibers, it is equally or more important to determine where a particle or fiber will deposit in the respiratory tract and how long it will stay there. The quantity and location of particle deposition in the respiratory tract depends on factors related to both the exposed individual and the inhaled particles. The mechanism of deposition is determined by the physical (size, shape, and density) and chemical (hygroscopicity and charge) characteristics of the inhaled particles. Particle deposition is also affected by biological factors inherent to the exposed individual such as breathing pattern (volume and rate), route of breathing (mouth versus nose), and the anatomy of the airways. 

A change in the system pressure also changes the volume and the intensity of the luminous gas phase (plasma), which not only changes the relative position of the polymer-collecting surface in the plasma, but also changes the ratio of polymer collected on the surface to the total amount of polymer formed. Consequently, a change in pressure may cause a change in the apparent deposition rate of plasma polymer. 

It is interesting to examine whether the polymer deposition rate is dependent on the surface-to-volume ratio SjV. Under the conditions employed for the experiment, SjV is given by Ijr, where r is the radius of the tube in the constriction. Therefore, the dependence of polymer deposition rate on S/V can be obtained by a plot of deposition rates versus Ijd, where d is the inner diameter of the constriction. Such plots are shown in Figure 20.26 for the plasma polymerization of tetramethyldisiloxane. 

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