Bifunctional catalytic effect of Mo₂C/oxide interface on multi-layer graphene growth

The role of the Mo₂C/oxide interface on multi-layer graphene (MLG) nucleation during a chemical vapor deposition (CVD) process is investigated. During the CVD process, MLG growth is only observed in the presence of a Mo₂C/SiO₂ interface, indicating that the chemical reactions occurring at this interface trigger the nucleation of MLG. The chemical reaction pathway is explained in four steps as (1) creation of H radicals, (2) reduction of the oxide surface, (3) formation of C-C bonds at O-H sites, and (4) expansion of graphitic domains on the Mo₂C catalyst. Different Mo₂C/oxide interfaces are investigated, with varying affinity for reduction in a hydrogen environment. The results demonstrate a catalyst/oxide bifunctionality on MLG nucleation, comprising of CH₄ dehydrogenation by Mo₂C and initial C-C bond formation at the oxide interface.