| Microwave plasma-enhanced chemical vapor deposition (MPCVD) is a key technique for
producing high-quality diamond films due to its ability to generate stable, high-density plasmas
under controlled low-pressure conditions. This study presents a numerical investigation of
MPCVD using COMSOL Multiphysics, focusing on plasma behavior and gas-phase chemistry in
H2/CH4/Ar mixtures for diamond growth phenomena. The computational framework employs
electromagnetic wave coupled with plasma module and heat transfer physics to solve the spatial
distributions of electron temperature, electron density, electric field, and key neutral and charged
species concentrations in a 2D axisymmetric reactor geometry under experimentally relevant
conditions. The model captures the formation and development of critical growth-relevant species,
including CH3, CH, C2H2, H, CH4
+
, and Ar+
, through a reaction network driven by electron impact
ionization, dissociation, and excitation reactions, with rate constants obtained from literature and
plasma databases. The spatial profiles and fluxes of gas-phase species toward the substrate are
analyzed to assess their implications for diamond growth. The role of argon is examined in terms
of its effect on plasma and overall enhancement of dissociation processes through its electron
impact behavior. Simulation results demonstrate the impact of variations in CH4/H2/Ar ratios on
production and distribution of growth-relevant species, highlighting the balance between precursor
generation and plasma uniformity. By extracting species fluxes at the substrate boundary and
applying simplified kinetic assumptions, the study provides growth rate estimations and discusses
how reactor parameters—such as gas composition, pressure, and input power—govern the plasma environment and influence the conditions necessary for controlled, high-purity diamond film
growth. This gas-phase-focused modeling approach offers predictive insight into the chemical
mechanisms underlying MPCVD and provides a foundation for optimizing deposition parameters
and reactor design in future studies, including the integration of surface kinetics with flow
dynamics and scale-up for large-area or single-crystal diamond synthesis.
Keywords: Plasma, Microwave, Chemical vapor deposition, Diamond, Growth rate, Chemical
kinetic |