Uniaxial and Biaxial Strain Engineering in 2D Materials with Thin Film Stressors

2D materials present a wide variety of strain sensitive electrical, optical, mechanical, magnetic, superconducting, and topological properties. We introduce an approach to selectively strain MoS₂ (uniaxially or biaxially) by depositing lithographically patterned thin film stressors. This technique is analogous to the ones used in industrial strained silicon but applied to 2D materials with weak out-of-plane bonding. To study the strain distribution in MoS₂ with Raman spectroscopic mapping, we chose optically transparent stressor films. Tensile stressors with a stripe geometry produce large tensile strains in MoS₂ at the edges and compressive strain at the center of the stressor strip. Uniaxial strains are observed in MoS₂ at stripe edges through polarized Raman while biaxial strains occur at stripe centers. We show that strain in 2D materials can be engineered to selectively exhibit tension/compression, uniaxiality/biaxiality, and directionality relative to crystal axes through simple lithographic patterning of stressed thin films.¹ Using this strain engineering technique, we demonstrate moving strain solitons and reconfiguring the stacking order in trilayer graphene.