MoS2-MX2in-plane superlattices: Electronic properties and bandgap engineering via strain

Abstract

Using density functional theory calculations, we performed a study of the electronic properties of transition metal dichalcogenides (TMDCs) in-plane superlattices MoS2-MX2 (MX2=WS2, MoSe2, WSe2). Particular attention has been focused on the bandgap engineering by applying biaxial strain. All the three superlattices show semiconducting characteristics retaining the direct bandgap character of TMDCs monolayer. Moreover, the bandgap can be widely tuned by applying biaxial strain and a universal semiconductor-metal (S-M) transition occur at a critical strain. Especially, the direct bandgap can also be modulated in a range by moderate strain. The shift of metal atoms d orbitals toward the Fermi level is mainly responsible for the bandgap variation although a different physical mechanism was induced by tensile and compressive strain. As a result MoS2-WS2 heterostructure needs a bigger critical strain for S-M transition due to the bigger bandgap.