POTENTIAL-ENERGY CALCULATIONS OF DIAMOND GROWTH BY METHYL RADICALS

The energetics of several possible methyl-driven surface reactions of diamond growth on the (111) plane was investigated by a semiempirical quantum-mechanical method. It was found that diamond growth by sequential additions of methyl radicals followed by radical-molecule interaction encounters a substantial potential energy barrier, 68-80 kcal/mol. The energetics of methyl-followed-by-acetylene addition was computed to be more favorable, although the energetically most favorable channel among those examined leads to the formation of stacking faults and structural defects. Diamond growth via the formation of a diradical surface species was computed to possess a low potential energy path that requires, however, a high steric selectivity for attacks on the surface sites by gaseous species. The computational results provide further support for the proposal that under typical deposition conditions the growth of diamond should be faster by the acetylene route than by the route involving methyl radicals.