Biaxial strain effects on van der Waals stacking in bilayer and tri-layer MoS₂

Stacking two-dimensional (2D) van der Waals (vdW) crystals is a promising technique for creating novel, artificially engineered materials and heterostructures for electronic and optoelectronic devices.

We study the effects of biaxial strain on different vdW stacking in bilayer (BL) and tri-layer MoS₂ grown by high temperature physical vapor deposition. The 2H and 3R polymorphs were identified by second harmonic generation and were associated with the physical orientation of triangular layers obtained via microscopy. We found that more than half of BLs corresponded to 3R stacking. Furthermore, we examined the interlayer shear and breathing modes of strained 2H & 3R BLs by using ultralow frequency Raman. Interlayer stacking energy obtained from first-principles calculations will be used to discuss the role of strain in the occurrence of different stackings as well as excitonic and phononic properties.