Growth rate pressure dependence

The implications of the correlation shown in Figure 8.7 are as follows (1) The energy input parameter (based on the luminous gas phase) does not control the deposition of material onto the cathode surface. (2) The current density of a DC glow discharge is the primary operational parameter. (3) The flow rate of monomer does not influence the film thickness growth rate. (4) The film thickness growth rate is dependent on the mass concentration of monomer (cM) in the cathode region rather than the mass input rate (FM). (In these experiments, the system pressure was maintained at a constant value of 50 mtorr, and thus c was a constant.)... 

Effects of Rate Conditions. It is essential for commercial a-quartz crystals to have usable perfection growth at a high rate and at pressure and temperature conditions that allow economical equipment design. The dependence of rate on the process parameters has been studied (8,14) and may be summarized as follows. Growth rate depends on crystallographic direction the (0001) is one of the fastest directions. Because AS is approximately linear with AT, the growth rate is linear with AT. Growth rate has an Arrhenius equation dependence on the temperature in the crystallization zone ... 

Crystal Morphology. Size, shape, color, and impurities are dependent on the conditions of synthesis (14—17). Lower temperatures favor dark colored, less pure crystals higher temperatures promote paler, purer crystals. Low pressures (5 GPa) and temperatures favor the development of cube faces, whereas higher pressures and temperatures produce octahedral faces. Nucleation and growth rates increase rapidly as the process pressure is raised above the diamond—graphite equiUbrium pressure. 

In the presented range of pressure variation. Hamers [163] also has studied the influence of the substrate temperature on the plasma and the material. It was found that in the temperature range of 200 to 300°C the trends of the bias voltage, the plasma potential, and the growth rate as functions of pressure all are the same, while the absolute magnitude depends on the temperature. The trends in material properties are similar to the ones reported above at a temperature of 200°C the material quality is worse than at higher temperatures. The a-y transition occurs at a lower pressure than at a temperature of 250°C. This has been observed before [248]. 

Since the biospheric growth rate depends, among other factors, on the C02 supply, it is probable that the C02 increase induces, at least for part of the biosphere, an increased growth rate ("C02 fertilization"). A simple concept to take this into account is the introduction of a biota growth factor e if the atmospheric C02 pressure increases by p percent, the C02 flux to the biosphere increases by zp percent. Typically, values for e between 0 and 0.5 have been used in carbon cycles models [26,41]. 

The effects of discharge frequency on the polymer growth rate were studied at a pressure of 0.5 torr, a flow rate of 20 cm3STP/min and a power level of 10 watts. All other parameters remained constant. The growth rates were plotted in the frequency range from 50 Hz to 13.56 MHz as shown in Fig. 3(a). The frequency dependence on growth rate may be divided into three regions of dis-... 

The control of the process is complicated and much effort has been spent to optimize the process. The pressure is kept low to enhance the material transport, as is nicely illustrated by Maltsev et al. in Figure 1.8 [27]. Typically, the pressure is kept below 50 mbar. In a study by Barrett et ah, the dependence of the growth rate on the system pressure was analyzed [28]. They could determine that convective effects were present at pressures above 20 Torr (approximately 26.7 mbar). Below 20 Torr the vapor transport is diffusive, according to their study. 

Figure 1.8 The temperature dependence on the growth rate is shown here for different Ar pressures. The residual pressures are for curve 1-10, 2-35, 3-50, 4-75, and 5-100 Torr. (From [27], 1996 Institue of Physics Publishing. Reprinted with permission.)...

Fig. 7. Dependence of total pressure (a) and film growth rate (b) on glow discharge duration in a closed system (Q = 0 Pq = 0.5 torr I = 1.7 mA) (monomer CjF ). [after Poll et al. ]...

Ideally, the functional dependence of the growth rate on the pressure (concentration) of the gaseous species would be determined by analysis of all the mechanistic steps, as was the case for our Ge example and as could be done for the W example. This is not always possible, however, due to insufficient information on such factors as reaction rate constants, adsorption energies, and preexponential factors. As a result, deposition rate data are often determined experimentally and are used to either support or refute... 

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