Microscopic model for the strain-driven direct to indirect band-gap transition in monolayer MoS₂ and ZnO

Abstract

At the monolayer limit both MoS₂ and the graphitic phase of ZnO have a direct band gap. Biaxial tensile strain has been found to induce a transition into an indirect band-gap semiconductor with the strain percentage required for the transition equal to 0.83% for MoS₂ and 8% for ZnO, respectively. A low strain percentage is desirable for possible device applications. We identify a simple design principle which could be used to identify materials requiring a small strain to induce such a transition. A scaling of the hopping interaction strengths according to Harrison's law within a tight-binding model for MoS₂ is able to capture the effect.