Complex Strain Scapes in Reconstructed Transition-Metal Dichalcogenide Moire Superlattices

We investigate the intrinsic strain associated with the coupling of twisted MoS2/MoSe2 heterobilayers by combining experiments and molecular dynamics simulations. Our study reveals that small twist angles (between 0 and 2 degrees) give rise to considerable atomic reconstructions, large moire periodicities, and high levels of local strain (with an average value of similar to 1%). Moreover, the formation of moire superlattices is assisted by specific reconstructions of stacking domains. This process leads to a complex strain distribution characterized by a combined deformation state of uniaxial, biaxial, and shear components. Lattice reconstruction is hindered with larger twist angles (>10 degrees) that produce moire patterns of small periodicity and negligible strains. Polarization-dependent Raman experiments also evidence the presence of an intricate strain distribution in heterobilayers with near-0 degrees twist angles through the splitting of the E-2g(1) mode of the top (MoS2) layer due to atomic reconstruction. Detailed analyses of moire patterns measured by AFM unveil varying degrees of anisotropy in the moire superlattices due to the heterostrain induced during the stacking of monolayers.