CCl radicals as a carbon source for diamond thin film deposition

We use first-principles quantum mechanical calculations to study diamond thin film growth on the (100) surface using CCl radicals as the carbon source. Our results show that CCl inserts into the surface dimer C-C bonds with a barrier of 10.5 kcal/mol, roughly half of the energy required for traditional CH₂ insertion (22.0 kcal/mol). In addition to this, CCl has improved surface mobility (∼30.0 kcal/mol barrier, versus 35 kcal/mol for CH ₂, along the C-C dimer chain direction), and hydrogen abstraction from the surface is also favored via atomic Cl in the vapor phase. These results explain the lower substrate temperatures achieved in crystal diamond growth from the use of chlorinated sources in CVD processes, as opposed to the more traditional CH₄/H₂ derived species. Our results also suggest that further reductions in substrate temperatures are possible from using CCl as the only carbon source.