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 Bi2Se3 grown on different monolayer transition metal dichalcogenides (TMDs), i.e. MoS2, MoSe2, WS2, and an alloy MoSe2(1−x)S2x, 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 Bi2Se3/MoSe2 layers have the strongest interlayer strength, followed by Bi2Se3/MoS2, Bi2Se3/WS2, and Bi2Se3/MoSe2(1−x)S2x. Finally, the recipe can be tuned to induce the Bi2Se3 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’.