Strain modulated optoelectronic properties of graphene and MoS₂ -- based bilayer and trilayer heterostructures

Strain engineering has emerged as a governing tool for tuning the phononic, electronic, and optical properties of two-dimensional (2D) materials. In this study, using first-principles calculations, we investigate the strain-modulated electronic and optical properties of graphene and MoS₂ -based heterostructures under uniaxial strain. From our calculations, we find that, due to the weak van der Waals interaction between graphene and MoS₂ monolayers, a band gap opens up at the Dirac point of graphene. The band gap is observed to upscale from 8 meV for graphene-MoS₂ bilayer to 11.4 meV for graphene-MoS₂-graphene trilayer. Whereas, a much smaller band gap of 5.1 meV is obtained for MoS₂-graphene-MoS₂ trilayer, suggesting a strong dependence on the arrangement of the layers in multilayer heterostructures. Under moderate uniaxial strain, band gaps widen from tens of meV to hundreds of meV across all systems. Furthermore, we observe a strain-dependent modulation of n-type Schottky contact at the graphene-MoS₂ interface, which offers a potential route to strain-engineered transport properties in these heterostructures. Our study also explores the optical properties of these systems. We observed an enhancement in the absorbance of heterostructures at low energies. Our study demonstrates the ability to control the band gap, Schottky barrier, and dielectric properties through strain engineering, which could be useful for developing the next generation of tunable optoelectronic and nanoelectronic devices based on graphene and MoS₂ heterostructures.