Exploration of MoS₂.WS₂ van der Waals Heterostructures through First Principles Calculations

Two-dimensional (2D) transition metal dichalcogenides (TMD), notably van der Waals (vdW) heterostructures are novel materials for electronic and optoelectronic applications due to their intriguing properties. In this paper, the effect of strain and electric field on the molybdenum disulfide (MoS₂) and tungsten disulfide (WS₂) vdW heterostructure from monolayer to multiple layer heterostructure stacking and optical absorption spectra were investigated through density functional theory (DFT) using VASP simulation program. Strain conditions are simulated by varying interlayer distance, and band structure analysis shows MoS₂.WS₂ becomes semi-metallic at -1.5 Å strain. In addition, a positive electric field decreases the valence and conduction band energies of MoS₂ and increases WS₂. Using this trend, we predict a breakdown voltage of 0.565 V/Å and -0.77 V/Å for MoS₂.WS₂ vdW heterostructures, indicating semi-metallic properties. Multi-layer MoS₂.WS₂ vdW heterostructures show a decreasing energy gap with increasing layer count. The energy band splitting of MoS₂ at the Λ point shifts the conduction band minimum (CBM) from K to Λ, while maintaining an indirect energy gap. We also calculated the dielectric function to assess the optoelectronic properties of MoS₂.WS₂ vdW heterostructures. The absorption spectra show that the MoS₂.WS₂ heterostructure has high absorption in most wavelength bands and remains stable with varying layer numbers. The obtained simulation results revealed that the strained MoS₂.WS₂ vdW heterostructure uncovers potential new optoelectronics applications.