The role of hydrogen in vapor deposition of diamond

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Abstract
The effect of hydrogen addition on growth of diamond films under the conditions of chemical vapor deposition was investigated computationally. A detailed chemical kinetic mechanism was composed to describe the evolution of reaction species in pyrolysis of hydrogen‐ and argon‐diluted methane mixtures with imposed temperature profiles, simulating the gas‐phase conditions of diamond film growth in an idealized hot‐filament reactor. The reaction mechanism was comprised of two basic parts: decomposition of methane, and formation and growth of polycyclic aromatic hydrocarbons; it contained a total of 120 elementary reactions and 45 chemical species. The reaction rate coefficients included temperature and pressure dependencies. The computations were performed for a variety of initial conditions, elucidating the effects of critical parameters on the product composition in the regime of diamond deposition. Analysis of the computational results indicated that the key role of the hydrogen addition in the diamond deposition process is to suppress the formation of aromatic species by H2 in the gas phase and thereby to prevent the formation and growth of nondiamond, graphitic phases on the deposition surface.

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