Deposition temperature, variation

This reaction suggests that a decrease in H2S concentration, and increases in H+ concentration and (H2 fugacity) and temperature variations are important causes for the deposition of gold in electrum. 

The variation of deposition temperature has similar effects on the material properties to those on PECVD-deposited material. With increasing temperature (125-650°C), the material becomes more dense (the refractive index extrapolated to 0 eV increases from 3.05 to 3.65). and the hydrogen content is decreased (15 to 0.3 at.%), as well as the microstructure factor (0.4 to 0). The activation energy is 0.83 eV up to a deposition temperature of 500°C. The dark conductivity and AM 1.5 photoconductivity are about 5 x 10 " and 5 x 10 cm , respec-... 

The run-to-run deposition zone temperature (350-425 °C) was the first parameter varied. Temperature variation affected film stoichiometry [Fig. 6.25(a)] and crystalline orientation [Fig. 6.25(b)], while not significantly affecting the deposition rate [Fig. 6.25(c)], From Fig. 6.25(a), we can see that the films were closest to stoichiometry when deposited at 395 °C. Cu-to-In ratios ranged from... 

The observed formation of calcite scales in geothermal wells is consistent with calcite saturation calculations (see Fig. 14). The intensity of calcite deposition is largely determined by two factors, the temperature of the water and its salt content (Arnorsson 1978a). In relation to temperature, calcite scale formation is most troublesome around 200 C and it decreases at both higher and lower T. The cause is the temperature variation in the solubility of C02. It is at a... 

HgS, deposited from thiosulphate solution, has been described with crystal sizes that depend on deposition temperature, from 3 nm to 8 nm and corresponding variation in apparent bandgaps from 2.4 to 1.9 eV. 

Heat transfer is an extremely important factor in CVD reactor operation, particularly for LPCVD reactors. These reactors are operated in a regime in which the deposition is primarily controlled by surface reaction processes. Because of the exponential dependence of reaction rates on temperature, even a few degrees of variation in surface temperature can produce unacceptable variations in deposition rates. On the other hand, with atmospheric CVD processes, which are often limited by mass transfer, small susceptor temperature variations have little effect on the growth rate because of the slow variation of the diffusion with temperature. Heat transfer is also a factor in controlling the gas-phase temperature to avoid homogeneous nucleation through premature reactions. At the high temperatures (700-1400 K) of most... 

Fig. 17.8. Variation of growth rate of doped polysilicon with PHj/SiH4 flow ratio deposition temperature 650°C wafer spacing 5 mm [16],...

Figure 27. (a) Temperature variation of resistance of an oriented Ndoj-Cac film deposited on LaAlOs(OOI) for different values of the current (b) resistance—temperature plots for three current values recorded over cooling and heating cycles showing memory effect. Inset in part a shows I—V curves at different temperatures (from Rao et al.54). 

Chemistry. There are many parts of mainline chemistry that originated in electrochemistry. The third law of thermodynamics grew out of observations on the temperature variations of the potential of electrochemical reactions occurring in cells. The concepts of pH and dissociation constant were formerly studied as part of the electrochemistry of solutions. Ionic reaction kinetics in solution is expressed in terms of the electrochemical theory developed to explain the activity of ions in solution. Electrolysis, metal deposition, syntheses at electrodes, plus half of the modem methods of analysis in solution depend on electrochemical phenomena. Many biomolecules in living systems exist in the colloidal state, and the stability of colloids is dependent on the electrochemistry at their contact with the surrounding solution. 

Up to now, the precursor solutions for Ba, Sr, and Ti are usually contained in separate reservoirs to permit variation in the input ratio of the cationic elements. However, for mass-production it is much more desirable to use the cocktail source which contains all three precursors in one reservoir for more reproducible deposition. Use of the cocktail source is not proper for research because changing the cationic composition is not easy. Furthermore, the cationic composition of BST films is not only dependent on the input precursor ratio hut also on the deposition temperature, as discussed helow. Therefore, use of a cocktail source is possible only... 

However, in region A, the chemical composition of the deposited thin films is very sensitive to the minute variation of temperature because in this region the thermal decomposition rate of the Ti precursor is very sensitive to temperature i.e. surface chemical reaction controls the deposition. The variation of mass concentration of the constituent ions estimated by x-ray fluorescent spectroscopy (XRF) is... 

Fig. 15 Typical variation of the cationic composition ratio with deposition temperature when the precursors are Ba(thd)2tetraglyme, Sr(thd)2tetraglyme and Ti(thd)2(0-i-P )2 dissolved in n-buthyl acetate.

Fig. 19 Variation of step coverage with deposition temperature.

Therefore the model of Chase and Perry, in which the geologic and isotopic data can be reconciled and which gives a quantitative estimate of the evolution, seems to be rather sound. Naturally, periodic fluctuations of S O caused by mass deposition of chemogenic carbonates, silicates, and silica in individual geologic epochs, and also by temperature variations, cannot be ruled out. 

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