Insights into the effects of substrate stacking, hydrogen passivation and carrier gas design on edge-vacancy sealing in h-BN growth.

Edge-vacancy sealing as the first step of row growth is critical for high-quality hexagonal boron nitride (h-BN) synthesis. Using ab initio molecular dynamics (AIMD) simulations, we investigated the finite-temperature dynamics of vacancy sealing at zigzag N-terminated (ZZN) edges on Cu (111) by atomic N, NH and NH2 radicals. Different stacking configurations lead to different types of quantum-mechanical coupling between Cu atoms and vacancy environments, thus influencing the sealing efficiency. In addition, hydrogen passivation improves the sealing of atomic N and NH radicals, while NH2 radicals remain ineffective. Finally, with kinetics analysis, we propose that a low-H2 carrier gas can provide enough effective radicals in the NH3 pyrolysis process and retain the etching effects of atomic H for edge defects. These findings may also shed light on the smooth crystal growth of other compound semiconductors.