Strain modulated optoelectronic properties of graphene and MoS$_2$ -- 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 MoS$_2$
-based heterostructures under uniaxial strain. From our calculations, we
find that, due to the weak van der Waals interaction between graphene and
MoS$_2$ monolayers, a band gap opens up at the Dirac point of graphene.
The band gap is observed to upscale from 8 meV for graphene-MoS$_2$ bilayer
to 11.4 meV for graphene-MoS$_2$-graphene trilayer. Whereas, a much smaller
band gap of 5.1 meV is obtained for MoS$_2$-graphene-MoS$_2$ 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-MoS$_2$ 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 MoS$_2$
heterostructures.
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