Tailoring the electronic and optical properties of ReS2 monolayer using strain engineering

In the present work, impact of various mechanical strains on the optoelectronic properties of monolayer ReS₂ (m-ReS₂) are investigated by using density functional theory. The bandgap of monolayer is determined to be 1.44 eV and 1.31 eV when computed using PBE and PBE + SOC methods. The monolayer displays outstanding electronic and optical tunability under biaxial compressive and shear strains. Under strain variations of 0 %–8 %, the bandgap for biaxial compression varies from 1.44 eV (1.31 eV) to 0.54 eV (0 eV), whereas for shear xx-yy strains, it varies from 1.44 eV (1.31 eV) to 0.34 eV (0.28 eV) when calculated using PBE (PBE + SOC) methods. A semiconductor-to-metal transition is observed for higher values of biaxial compressive strain. A pronounced impact of strain on the optical characteristics is likewise observed. We noticed that the absorption edge of monolayer ReS₂ shifts from 1.32 eV to 0.50 eV with a 0 %–8 % increase in biaxial compression, leading to an 11 % red shift in wavelength per 1 % strain change. Moreover, high optical absorption (5 × 10⁵ cm⁻¹), lying from infrared to UV region is observed. The present study points out that strain engineering can be an efficient tool for modifying both the electronic and optical properties of m-ReS₂ and may open new avenues for using this material in future optoelectronic applications.