Strain engineering in monolayer WS2, MoS2, and the WS2/MoS2 heterostructure

Mechanically exfoliated monolayers of WS₂, MoS₂ and their van der Waals heterostructure were fabricated on flexible substrate so that uniaxial tensile strain can be applied to the two-dimensional samples. The modification of the band structure under strain was investigated by micro-photoluminescence spectroscopy at room temperature as well as by first-principles calculations. Exciton and trion emissions were observed in both WS₂ and the heterostructure at room temperature, and were redshifted by strain, indicating potential for applications in flexible electronics and optoelectronics.