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Development and Applications of ReaxFF Reactive Force Fields for Group-III Gas-Phase Precursors and Surface Reactions with Graphene in MOCVD Synthesis

This JPCC study introduces two ReaxFF parameter sets, GaCH-2020 and InCH-2020, for trimethylgallium and trimethylindium chemistry in metal–organic chemical vapor deposition (MOCVD) scenarios, including gas-phase decomposition and interactions with graphene substrates.

Summary

GaCH-2020 and InCH-2020 extend the ReaxFF bond-order framework to Ga–C/H and In–C/H organometallic chemistry together with graphene surface reactions so that reactive molecular dynamics can probe MOCVD-like thermal decomposition of TMGa and TMIn toward Ga- and In-rich nanoclusters with low carbonaceous impurity content. The authors apply the new potentials to map how processing conditions affect cluster purity from precursor pyrolysis and to survey cluster formation on graphene that contains vacancies and zigzag versus armchair edge terminations. They report that graphene with Ga-functionalized monovacancies can template directional Ga cluster growth through covalent pathways, and that under selected growth conditions Ga on armchair-edged bilayer graphene not only grows faster than In but can spread into a thin two-dimensional layer between edges.

Methods

1 — MD application. ReaxFF reactive MD (standard LAMMPS-compatible implementation in the JPCC article) covers gas-phase TMGa and TMIn pyrolysis and graphene-supported deposition on pristine, monovacancy, and edge-terminated (zigzag vs armchair) sheets, including bilayer armchair geometries where discussed. 3D PBC supercells; NVT heating and isothermal stages; sub-1 fs timestep; Nose–Hoover-type thermostat; NPT only if the article pressurizes vapor cells (see VOR—N/A here to quote bar values). Duration: ps-scale and longer equilibration and production segments per the JPCC Methods (exact ns spans in the VOR/SI). Temperature in K for ramped and held stages drives pyrolysis and coalescence. Electric field; replica / enhanced sampling — N/A in the summarized protocol scope.

2 — Force-field training. GaCH-2020 and InCH-2020 parameter sets add Ga/In–C/H + graphene-C interactions; EEM charges; QM reference set for organo-Group-III + carbon (training data and ReaxFF optimization workflow in Methods/SI).

3 — Static QM. DFT data underpinning the fit are summarized in the main J. Phys. Chem. C paper; N/A as a pure DFT-only study.

4 — Galley. The registered pdf_path is a galley—confirm table and run parameters against the VOR file.

Findings

Pyrolysis and purity: Thermal and compositional windows are identified in which Ga/In clusters form with low carbon-rich byproduct content relative to less selective channels. Graphene-templated morphology: Ga covalent attachment at monovacancy sites supports anisotropic Ga growth vs. more isotropic nucleation on clean basin areas. On armchair-edged bilayer graphene, the authors report faster Ga accumulation than In and, under selected conditions, a spread-out two-dimensional Ga sheet between edge boundaries. Comparisons are intra-study (Ga vs In, edge vs vacancy). Limitations: nitride-containing (NH\(_3\), N-doped) CVD is explicitly excluded from the parametrization scope; the ingested corpus PDF is a galley (see ## Limitations).

Limitations

Group-III nitride chemistry is not included; the authors note that extending the model with nitrogen-containing training data is a natural next step. The ingested corpus PDF is an ACS galley; final pagination and minor editorial details should be checked against the version of record.

Relevance to group

The work links Penn State ReaxFF development to III–V precursor chemistry and graphene-templated growth, complementing nitride and transition-metal dichalcogenide studies elsewhere in the knowledge base.

Citations and evidence anchors

Reader notes (navigation)

  • paper_keywords includes keyword:galley-or-proof-pdf.