Strain induced effects on the electronic and phononic properties of 2H and 1T[formula omitted] monolayer MoS2

Abstract

First-principles calculations have been performed on the 2H and the 1T′ phase of single-layer MoS2. We have addressed the strain-induced tunability of the electronic and the phononic properties of both phases, and compared their stability. For the 2H phase, a direct to indirect band gap transition, followed by the band gap lowering leading to a semiconductor to metal transition, is observed. The applied strain destroys the semimetallic nature of the 1T′ phase. Significant strain-induced changes in the frequency and the dispersion of the phonon branches are observed. With increasing strain, the out-of-plane acoustic mode (ZA) turns imaginary, suggesting a possibility of phase transition or instability of the crystal structure. The 2H phase appears to withstand a larger amount of strain indicating better stability compared to the 1T′ phase. We also highlight the significance of anisotropic strain-engineering in tuning the electronic and phononic properties and the stability limit of monolayer 1T′-MoS2.