▎ 摘　　要

In-plane graphene/hexagonal boron nitride (h-BN) heterostructures show promising applications in novel two-dimensional electronic and optoelectronic devices. The quality of graphene/h-BN (G-BN) domain boundaries, which plays a critical role in device performances, depends on their coalescence. Here, the coalescing mechanism determined by the overlayer-substrate interaction and the growth dynamics during the heterostructure synthesis were studied by in situ surface imaging measurements. In-plane G-BN heterostructures were grown (h-BN first and graphene then) on Pt(111) and Ru(0001) surfaces by chemical vapor deposition. Oxygen intercalation acted as a probe reaction to investigate the coalescing behaviors of the G-BN domain boundaries. Oxygen atoms can intercalate from the outer graphene edges and cross the G-BN domain boundaries into the interior h-BN zone on Pt(111) surfaces. On Ru(0001) surfaces, only interior h-BN domains could be intercalated from G-BN domain boundaries, while no intercalation occurred on outer graphene domains. This shows that graphene can seamlessly stitch with h-BN on Pt(111) but not on Ru(0001), because the weaker overlayeresubstrate interaction on Pt(111) compared to that on Ru(0001) makes the G-BN coalescing interface flatter and allows stitching at an identical height. High-quality in-plane G-BN heterostructures are expected to grow on weakly interacting surfaces rather than on strong ones. (c) 2021 Elsevier Ltd. All rights reserved.