Interface-Controlled Epitaxy of Hexagonal Boron Nitride

The scalable synthesis of single-crystalline monolayer hexagonal boron nitride (hBN) films demands precise orientation control, a challenge due to the unresolved underlying mechanism. This study establishes a universal theoretical framework by integrating density functional theory and molecular dynamics simulations. We reveal that the hBN orientation is governed by a size-dependent competition among edge-step coupling, edge-terrace coupling, and long-range van der Waals interactions. Crucially, the chemical environment (B-rich vs N-rich) selectively stabilizes specific edge terminations, thereby dictating the ultimate orientation. N-rich conditions universally ensure unidirectional alignment, whereas B-rich conditions can lead to antiparallel domains, especially on weakly interacting substrates. This work provides a theoretical framework and actionable guidance─prioritizing N-rich growth and step engineering─for the wafer-scale synthesis of hBN and related noncentrosymmetric two-dimensional materials.