Simultaneous tunability of the electronic and phononic gaps in SnS sub(2) under normal compressive strain

Controlled variation of the electronic properties of two-dimensional (2D) materials by applying strain has emerged as a promising way to design materials for customized applications. Using density functional theory (DFT) calculations, we show that while the electronic structure and indirect band gap of SnS sub(2) do not change significantly with the number of layers, they can be reversibly tuned by applying biaxial tensile (BT), biaxial compressive (BC), and normal compressive (NC) strains. Mono to multilayered SnS sub(2) exhibit a reversible semiconductor to metal (S-M) transition with applied strain. For bilayer (2L) SnS sub(2), the S-M transition occurs at the strain values of 17%, -26%, and -24% under BT, BC, and NC strains, respectively. Due to weaker interlayer coupling, the critical strain value required to achieve the S-M transition in SnS sub(2) under NC strain is much higher than for MoS sub(2). From a stability viewpoint, SnS sub(2) becomes unstable at very low strain values on applying BC (-6.5%) and BT strains (4.9%), while it is stable even up to the transition point (-24%) in the case of NC strain. In addition to the reversible tuning of the electronic properties of SnS sub(2), we also show tunability in the phononic band gap of SnS sub(2), which increases with applied NC strain. This gap increases three times faster than for MoS sub(2). This simultaneous tunability of SnS sub(2) at the electronic and phononic levels with strain, makes it a potential candidate in field effect transistors (FETs) and sensors as well as frequency filter applications.