Recent studies of van der Waals heterostructures involving transition metal dichalcogenide (TMD) overlayers have revealed the formation of highly ordered mirror twin boundaries (MTBs) dividing domains in the single 2H phase. Here, using a multiscale modeling approach, we identify that the MTB network formation results from a delicate interplay between strain accumulation in the heterostructure and single-crystal preference of the growing overlayer. We determine the energy costs for the creation of the MTB by first-principles calculations, from which we show that even the presence of a perceived-to-be negligible strain is able to induce the formation of the MTB networks as an effective strain-relief mechanism of the growing TMD monolayers, as observed experimentally. This counterintuitive finding demonstrates the importance of collective effects in weakly interacting systems, i.e., in van der Waals epitaxy.

• Received 27 April 2019

DOI:https://doi.org/10.1103/PhysRevB.100.035429