Carbon films source gases

Erdemir, A., Nilufer, I. B., EryUmaz, O., Beschliesser, L. M., and Fenske, G. R., Friction and Wear Performance of Diamond-like Carbon Films Grown in Various Source Gas Plasmas," Srrr/ Coat. Technol., Vol. 121,1999, pp. 589-593. 

Fig. 28. Anodic O3 evolution plots for polycrystalline diamond thin-film electrodes (top) and PbC>2 electrodes exposed to 10 vol. % H2SO4 solution. The boron/carbon ratio in the source gas during the films growth shown on the figure [119]. Reproduced by permission of The Electrochemical Society, Inc.

Figure 5.15. Diagram of a-parameter curves and film morphology. The SEM images (a)-(d) are the film surfaces grown under the CVD conditions indicated by a-d in the diagram. The numbers in the diagram are the a-parameter values associated with the regions encircled by the dashed curves. The horizontal axis is an effective carbon concentration, C, defined by the concentrations of CH4, H2, and CO2 in the source gas. For this experiments, the large MPCVD reactor shown in Figure 3.4 was used [68, 70].

The chemical vapor deposition has developed into the leading method for the preparation of thin diamond films. It is mainly characterized by a precipitation of carbon from the gas phase onto a substrate. Applicable sources of carbon include methane, acetylene, or ethylene, which are normally admixed with a current of hydrogen. The latter, in an atomic state, turned out to be essential for an efficient production of high-quality diamond films. Actually, atomic hydrogen is generated in situ from... 

The carbon source affects oxygen demand. In penicillin production, oxygen demand for glucose is 4.9 mol 1 1 h-1. The lactose concentration is 6.7 mol 1 1 h 1, sucrose is 13.4 mol l-1 h. The yield of oxygen per mole of carbon source for CH4 is YQjC = 1.34, T0j/C for Paraffins = 1, and Y(> /c for hydrocarbon (CH20)n = 0.4. The mass transfer coefficient k,a is for gas-liquid reactions, and the film thickness where the mass transfer takes place is 8... 

There have been many other reports of single-source azido precursors, all aimed at achieving device-quality films using moderate deposition conditions. The azide precursors have the advantages of (i) having preformed Ga—N bonds and (ii) only a limited number of the undesirable Ga—C and N—C bonds which can lead to carbon incorporation into the nitride films.311 A list of azido-based precursors and deposition conditions is given in Table 14. 

Apart from the reactions described above for the formation of thin films of metals and compounds by the use of a solid source of the material, a very important industrial application of vapour phase transport involves the preparation of gas mixtures at room temperature which are then submitted to thermal decomposition in a high temperature furnace to produce a thin film at this temperature. Many of the molecular species and reactions which were considered earlier are used in this procedure, and so the conclusions which were drawn regarding choice and optimal performance apply again. For example, instead of using a solid source to prepare refractory compounds, as in the case of silicon carbide discussed above, a similar reaction has been used to prepare titanium boride coatings on silicon carbide and hafnium diboride coatings on carbon by means of a gaseous input to the deposition furnace (Choy and Derby, 1993) (Shinavski and Diefendorf, 1993). 

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