▎ 摘　　要

Thin Mo2C hexagonal defects precipitate in CVD graphene when Mo crucibles are engaged to hold the liquid copper substrate, while these defects disappear when W crucibles are present. These defects have been identified as the thin precipitates of Mo2C. The growth mechanism of the Mo2C defects is demonstrated through thermodynamic calculations. This can be beneficial in graphene defect engineering through the vapour phase transport of the volatile MoO3 phase.