Surface Chemical Processes of Diamond-Film Growth in Plasma

Surface Chemical Processes of Diamond-Film Growth in Plasma 

The most conventional non-equilibrium plasma-chemical systems that produce diamond films use H2-CH4 mixture as a feed gas. Plasma activation of this mixture leads to the gas-phase formation of hydrogen atoms, methyl radicals (CH3), and acetylene (C2H2), which play a major role in further film growth. Transport of the gas-phase active species to the substrate is mostly provided by diffusion. The substrate is usually made from metal, silicon, or ceramics and is specially treated to create diamond nucleation centers. The temperature of the substrate is sustained at the level of 1000-1300 K to provide effective diamond synthesis. The synthesis of diamond films is provided by numerous elementary surface reactions. Four chemical reactions in particular describe the most general kinetic features of the process. First of all, surface recombination of atomic lydrogen from the gas phase into molecular hydrogen returns back to the gas phase  

This fast barrierless process is also partially balanced by the reverse reaction of desorption of an H atom from the surface group C-H. A major contribution to the actual deposition of the diamond film can be attributed to the initial chemisorption of methyl radicals (CH3) and acetylene (C2H2) to open caibon bonds on the surface of the film  

After the primary chemisorption, (9-117) and (9-118), of the carbon components, a sequence of surface reactions incorporates the carbon atoms into the growing layer of the diamond crystal stmcture, which is discussed in the next section (see also Farouk, Nagayama, Lee, 1995,1996,1997 Farouk etal., 1998 Farouk Beta, 1999 Robertson, 

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