Growth and Deposition Mechanisms

The photon-emitting species are vitally important in luminous chemical vapor deposition (LCVD) process, and the location of the luminous gas phase indicates where actions occur within the interelectrode space. On the other hand, whether any particular photon-emitting species is primarily responsible for LCVD is a dilferent issue. As is described in Chapter 5 for the growth and deposition mechanisms, many chemically reactive species, such as various forms of free radicals that do not emit photons, are major reactive species that carry the growth reactions. No single species could be identified as the precursor or chemically reactive species for the process. 

XPS data, on the other hand, showed that the ETC AT treatment of Ar + CF4 and Ar + C2F4 yielded just as good, if not better, fluorination of PET fibers than radio frequency plasma treatment with these gases [14,15]. These examples clearly demonstrate that polymerizable species in plasma polymerization are not photon-emitting species in most cases. This is in accordance with the growth and deposition mechanism based on free radicals, which account for the presence of large amount of dangling bonds in most plasma polymers. 

In the chain growth free radical polymerization of a vinyl monomer (conventional polymerization), the growth reaction is the repeated reaction of a free radical with numbers of monomer molecules. According to the termination by recombination of growing chains, 2 free radicals and 1000 monomer molecules leads to a polymer with the degree of polymerization of 1000. In contrast to this situation, the growth and deposition mechanisms of plasma polymerization as well as of parylene polymerization could be represented by recombinations of 1000 free radicals (some of them are diradicals) to form the three-dimensional network deposit via 1000 kinetic... 

Fig. 4 Growth and deposition mechanisms in the luminous gas phase. (View this art in color at WWW. dekker. com.)...

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