Tuning Optical Properties of MoS2 Bulk and Monolayer Under Compressive and Tensile Strain: A First Principles Study

Knowledge of the optical properties under compressive and tensile strain is highly important in photoelectron devices and the semiconductor industry. In this work, optical properties of bulk and monolayer MoS2 under compressive and tensile strains are investigated by means of density functional theory. The dielectric tensor is derived within the random phase approximation. Calculations indicate that unstrained two-dimensional and bulk MoS2 lead to semiconductors with the gaps of 1.64 eV and 0.84 eV, respectively, whereas the change in the value of the gap by applying tensile or compressive strain depends on the nature of strains. Dielectric function, absorption coefficient, reflectivity, energy loss and the refraction index of the strained and unstrained systems are studied for both parallel (E||x) and perpendicular (E||z) applied electric field polarizations, which are very sensitive to the type and amount of strains. For instance, the reflectivity of a MoS2 monolayer exposed to visible light in the E||z polarization direction, can be tuned from 4% to 10% by introducing strain. Finally, the Abbe number is calculated to characterize the dispersion of the materials under compressive and tensile strain. Bulk MoS2 for E||x shows the highest value of the Abbe number, which shrinks twenty times under the influence of compressive strain.