Strain engineering of the mechanical properties of two-dimensional WS2

Abstract

Tuning the physical properties of two-dimensional (2D) materials is crucial for their successful integration into advanced applications. While strain engineering demonstrated an efficient means to modulate the electrical and optical properties of 2D materials, tuning their mechanical properties has not been carried out. Here we applied compressive strain through the buckling metrology to 2D tungsten disulfide (WS₂), which demonstrated mechanical softening manifested by the reduction of its effective Young's modulus. Raman modes analysis of the strained WS₂ also showed strain-dependent vibrational modes softening and revealed its Grüneisen parameter (γ_E2g = 0.29) and its shear deformation potential (β_E2g = 0.56) – both are similar to the values of other 2D materials. In parallel, we conducted a molecular dynamic simulation that confirmed the validity of continuum mechanics modeling in the nanoscale and revealed that due to sequential atomic-scale buckling events in compressed WS₂, it shows a mechanical softening. Therefore, by tuning the mechanical properties of WS₂ we shed light on its fundamental physics, thus making it an attractive candidate material for high-end applications, such as tunable sensors and flexible optoelectronic devices.