Probing the interlayer interaction between dissimilar 2D heterostructures by in situ rearrangement of their interface

Abstract We present a method to study the interlayer interaction of 2D heterostructures by analyzing the rotational statistics of the as-grown twist angles, as well as in situ manipulation of their relative twist angles using an electron beam. We investigated this in a family of 2D heterostructures: 1–2 layers of Bi ₂ Se ₃ grown on different monolayer transition metal dichalcogenides (TMDs), i.e. MoS ₂ , MoSe ₂ , WS ₂ , and an alloy MoSe _{2(1− x )} S _{2 x} , which enabled us to compare the relative coupling strengths at junctions with not only similar and dissimilar ‘nearest-layer’ chalcogens, but also with ‘next-nearest-layer’ transition metals, as well as ‘nearest-mixed-layer’ chalcogens. We found that while higher e-beam current densities tend to ‘disrupt’, and lower values ‘recrystallize’ the crystal structure, TMD-specific intermediate-value-ranges can dynamically twist the layers with respect to each other. From their initial as-grown twist angle, as well as the ease with which they can be perturbed to twist in response to various electron beam current densities, we infer that Bi ₂ Se ₃ /MoSe ₂ layers have the strongest interlayer strength, followed by Bi ₂ Se ₃ /MoS ₂ , Bi ₂ Se ₃ /WS ₂ , and Bi ₂ Se ₃ /MoSe _{2(1− x )} S _{2 x} . Finally, the recipe can be tuned to induce the Bi ₂ Se ₃ to form nanoparticles that emit a broad photoluminescence and alter the 2D heterostructure’s perceived color. Our results reveal that interlayer interactions play a substantial role even in heterostructures of chemically and crystallographically dissimilar 2D materials, where they are traditionally expected to be ‘weak’.