Anisotropic Photoluminescence Emission in MoS 2 Enabled by Nanoimprinted Dielectric Gratings

Two-dimensional (2D) transition metal dichalcogenide (TMD)-based polarization-sensitive optoelectronic devices are highly promising for enhancing spatial resolution in imaging and sensing applications. However, their development is limited by the inherent lattice asymmetry of TMDs. Here, the imprinted wafer scale all-dielectric nanogratings (DGs) with the designed structural parameters are introduced in MoS 2 crystals to manipulate the optical properties. Two types of systems are formed by transferring the MoS 2 nanoflakes on imprinted DGs. Type I involves MoS 2 nanoflakes suspended within the nanogrooves, while for Type II, MoS 2 flakes are flatly spread over the gratings. Because of the cavity effect, the intensities of photoluminescence (PL) emission, Raman and second-harmonic generation are highly enhanced in Type II systems. Further, the anisotropic optical response of the DGs, leading to polarization dependence of PL emission for two types of hybrid systems and a higher degree of polarization (DOP) up to 0.59 is achieved in Type I systems. Additionally, the Fermi level difference of 18 meV induced by the strain results in periodic back-to-back built-in electric fields in Type I systems. After biasing, the gradient band energy structure significantly improves the separation efficiency of photogenerated charge carriers. These findings provide a comprehensive understanding of the mechanism causing optical differences in two types of hybrid systems and opens up new avenues for the development of high-performance photonics and optoelectronics devices.