Surface Migration in Diamond Growth

Abstract

Growth of diamond has usually been discussed without invoking any form of surface diffusion. Our recent theoretical results identified, however, that bridging CH 2 and CCH 2 groups and radical vacancies can migrate on diamond {100} surfaces. The present work further explores migration of hydrogen atoms, bridging groups, and surface radicals, investigating the migration in two dimensions. The analysis is based on quantummechanical computations of potential energy barriers and vibrational frequencies, transition-state-theory evaluation of reaction rates, chemical-kinetic analysis of localized reaction networks, and idealized randomwalk calculations of migration lengths. It is demonstrated that migration of hydrogen atoms and the bridging groups is nearly isotropic in two directions, along dimer rows and along dimer chains, while migration of surface radicals introduces distinct anisotropy to the overall character of surface diffusion. In their entirety, the results substantiate the governing role of surface migration in chemical vapor deposition of diamond.

Etching effects during the chemical vapor deposition of (100) diamond

“…The TB/DFT method predicts a heat of reaction, AIYI,that is three times smaller than that estimated by Harris and Goodwin [19], and an entropy change, AS1,that is nearly the same. The TB/DFT value for AH, agrees well with the PM3 calculations of Frenklach et al [44,55,56]. We estimated the PM3 value for ASI using the kinetic simulations of Frenklach et al [44,55,56], who did not report this quantity.…”

“…The TB/DFT value for AH, agrees well with the PM3 calculations of Frenklach et al [44,55,56]. We estimated the PM3 value for ASI using the kinetic simulations of Frenklach et al [44,55,56], who did not report this quantity. A CHZ adsorbate is expected to lose some rotational and translational degrees of freedom when it is incorporated at the surface (see Fig.…”

“…The reaction mechanism in Table I does not include the surface migration processes that have been proposed recently by Frenklach et al [35,44]. The development of smooth (100) surface features could certainly be accomplished by supplementing the growth model with a mechanism for the diffusion and attachment of growth species to step edges.…”

“…only serve to increase the predicted (100) growth rates (which are, as discussed above, already too high). Thus, while surface migration might be important on the (100) surface of diamond [44], it cannot provide an answer to the fundamental problems discussed above, and thus we have not considered it in the present study…”

“…Estimates from molecular mechanics (MM3) [19] and parametrized model (PM3) [44,55,56] calculations are provided for comparison. The TB/DFT method predicts a heat of reaction, AIYI,that is three times smaller than that estimated by Harris and Goodwin [19], and an entropy change, AS1,that is nearly the same.…”