Ab initio energetics of CVD growth reactions on the three low-index surfaces of diamond

Two novel CVD diamond growth mechanisms are proposed which involve methyl radicals and acetylene molecules where carbon atoms are inserted into {100} 2 × 1 monohydride dimer surface reconstruction bonds. We have built models of the three principal surfaces of diamond and performed ab initio local density-based calculations to determine structures and energies of surface reactions including the two postulated for 2 × 1 reconstructed {100}. Both of these processes are found to be exothermic but with large barriers. However, they do demonstrate that reconstruction bonds can facilitate growth. The results are discussed with respect to the large body of recent experimental results and we conclude that the relative contributions of methyl and acetylene depend on the system used