Strain engineering tuned vibrational dynamics of 2D transition metal dichalcogenide heterostructures: A first-principles investigation.

Controlling vibrational modes and energy gap by creating van der Waals (vdW) heterostructures through strain engineering is a novel approach to tailor the vibrational and electronic properties of two-dimensional (2D) materials. Numerous theoretical and experimental studies have significantly contributed to analysing the properties of transition metal dichalcogenides (TMDs), known for their multifunctional applications. In this study, we investigate the strain and stacking dependent vibrational properties of WSe2/MoSe2 and MoSe2/WSe2/MoSe2 vdW heterostructures using first-principles based density functional theory calculations. The dynamical stability of all vdW heterostructures makes them feasible in fabrication. Our phonon calculations and zone centre phonon modes analysis signify that the interlayer interaction influences interlayer breathing and shear phonon modes, which play an important role in thermal properties. The effect of strain engineering on the vibrational modes and energy gap of vdW heterostructures are further discussed. The tensile and compressive biaxial strain on the vdW heterostructures results in phonon softening and hardening, respectively.