Gas-jet HFCVD synthesis of diamonds from mixtures of hydrogen with ethylene and methane

The gas-jet deposition method (a modification of the Hot Filament Chemical Vapor Deposition method (HFCVD)) was used to deposit some diamond structures on a molybdenum substrate from a hydrogen-ethylene mixture activated on hot tungsten. The experiments were performed for two lengths of activation reactors at different ethylene flow rates. For comparison, some diamond structures were synthesized from a hydrogen-methane mixture under similar conditions. The resulting structures were studied with the scanning electron microscopy and Raman spectroscopy methods. The reacting mixture flow through the heated catalytic channel was simulated by solving the Navier-Stokes equations accounting for homogeneous and heterogeneous chemical reactions. The reactor (hot tungsten tube) length and diameter effects as well as carbonaceous admixture supply effects were analyzed. The main diamond precursor's formation pathways were analyzed and the reaction chains' complexity was demonstrated. The simulation results are in good agreement with the experimental data. The numerical experiments made it possible to reveal the growth process key driving parameters.