2 research outputs found
Emergence of Highly Linearly Polarized Interlayer Exciton Emission in MoSe<sub>2</sub>/WSe<sub>2</sub> Heterobilayers with Transfer-Induced Layer Corrugation
The availability of accessible fabrication methods based on deterministic
transfer of atomically thin crystals has been essential for the rapid expansion
of research into van der Waals heterostructures. An inherent issue of these
techniques is the deformation of the polymer carrier film during the transfer,
which can lead to highly non-uniform strain induced in the transferred
two-dimensional material. Here, using a combination of optical spectroscopy,
atomic force and Kelvin probe force microscopy, we show that the presence of
nanometer scale wrinkles formed due to transfer-induced stress relaxation can
lead to strong changes in the optical properties of MoSe/WSe
heterostructures and the emergence of the linearly polarized interlayer exciton
photoluminescence. We attribute these changes to the local breaking of crystal
symmetry in the nanowrinkles, which act as efficient accumulation centers for
the interlayer excitons due to the strain-induced interlayer band gap
reduction. The surface potential images of the rippled heterobilayer samples
acquired using Kelvin probe force microscopy reveal the variation of the local
work function consistent with the strain-induced band gap modulation, while the
potential offset observed at the ridges of the wrinkles shows a clear
correlation with the value of the tensile strain estimated from the wrinkle
geometry. Our findings highlight the important role of the residual strain in
defining optical properties of van der Waals heterostructures and suggest novel
approaches for interlayer exciton manipulation by local strain engineering