Microcrystalline, nanocrystalline, and ultrananocrystalline diamond chemical vapor deposition: Experiment and modeling of the factors controlling growth rate, nucleation, and crystal size

Ar/CH₄/H₂ gas mixtures have been used to deposit microcrystalline diamond, nanocrystalline diamond, and ultrananocrystalline diamond films using hot filament chemical vapor deposition. A three-dimensional computer model was used to calculate the gas phase composition for the experimental conditions at all positions within the reactor. Using the experimental and calculated data, we show that the observed film morphology, growth rate, and across-sample uniformity can be rationalized using a model based on competition between H atoms, CH₃ radicals, and other C₁ radical species reacting with dangling bonds on the surface. Proposed formulas for growth rate and average crystal size are tested on both our own and published experimental data for Ar/CH₄/H₂ and conventional 1% CH₄/H₂ mixtures, respectively.