Bandgap engineering of MoS2/MX2 (MX2 = WS2, MoSe2 and WSe2) heterobilayers subjected to biaxial strain and normal compressive strain

Abstract

Using first-principles calculations, we studied the electronic properties of quasi-2D MoS₂/MX₂ (MX₂ = WS₂, MoSe₂ and WSe₂) heterobilayers, focusing on engineering the band gap via application of in-plane biaxial strain and out-of-plane normal compressive strain (NCS). All heterobilayers show semiconducting characteristics with an indirect band gap except for the MoS₂/WSe₂ system which exhibits direct band gap character. The band gaps can all be widely tuned through strain and semiconductor–metal transitions can occur. In particular the direct band gap can be tuned and an appropriate compressive strain can tune the direct band gap of MoS₂/WSe₂ and MoS₂/MoSe₂, but MoS₂/WS₂ does not exhibit a direct band gap under any circumstances.