Origin of ultrafast growth of monolayer WSe2 via chemical vapor deposition

The ultrafast growth of large-area, high-quality WSe2 domains with a compact triangular morphology has recently been achieved on a gold substrate via chemical vapor deposition. However, the underlying mechanism responsible for ultrafast growth remains elusive. Here, we first analyze growth processes and identify two possible pathways that might achieve ultrafast growth: Path 1, fast edge attachment and ultrafast edge diffusion; Path 2, fast kink nucleation and ultrafast kink propagation. We perform kinetic Monte Carlo simulations and first-principles calculations to assess the viability of these two paths, finding that Path 1 is not viable due to the high edge diffusion barrier calculated from first-principles calculations. Remarkably, Path 2 reproduces all the experimental growth features (domain morphology, domain orientation, and growth rate), and the associated energetic data are consistent with first-principles calculations. The present work unveils the underlying mechanism for the ultrafast growth of WSe2, and may provide a new route for the ultrafast growth of other two-dimensional materials