Development and Applications of ReaxFF Reactive Force Fields for Group-III Gas-Phase Precursors and Surface Reactions with Graphene in Metal-Organic Chemical Vapor Deposition Synthesis

Two-dimensional (2D) materials exhibit a wide range of optical, electronic, and quantum properties divergent from their bulk counterparts. To realize scalable 2D materials, metal-organic chemical vapor deposition (MOCVD) is often used. Here, we report two ReaxFF reactive force fields, GaCH-2020 and InCH-2020, which were developed to investigate the MOCVD gas-phase reactions of Ga and In film growth from trimethylgallium (TMGa) and trimethylindium (TMIn) precursors, respectively, and the surface interactions of TMGa and TMIn with graphene. The newly developed force fields were applied to determine the optimal conditions for the thermal decomposition of TMGa/TMIn to achieve Ga/In nanoclusters with low impurities. Additionally, the cluster formation of Ga/In on a graphene substrate with different vacancies and edges was studied. It was found that a graphene with Ga-functionalized monovacancies could help conduct directional Ga cluster growth via covalent bonds. Moreover, under specific growth conditions, we found that Ga atoms growing on armchair-edged graphene not only exhibited a superior growth ratio to In atoms but also produced a widely spread 2D thin layer between graphene edges.