Epitaxial Growth of MoS₂ on h-BN without Mirror Grain Boundaries

Recent efforts in perfecting the epitaxial growth of polar 2D materials appear to stop short at one last hurdle: the interaction between the grown 2D sheets and the carefully chosen, nearly-commensurate substrates is at best strong enough to energetically favor only two crystal orientations related by in-plane inversion, yet too weak to lift this remaining near-degeneracy, allowing formation of mirror grain boundaries that degrade carrier mobility. Using first-principles calculations, we examine the prospect of defects in a hexagonal boron nitride substrate facilitating the nucleation and epitaxial attachment of transition metal dichalcogenide monolayers on top, with full orientation control.