Van der Waals Interlayer Coupling Induces Distinct Linear Dichroism in WSe2 Photodetectors

Driven by the unique linear dichroism feature of anisotropic two-dimensional (2D) materials, much attempt has been made to introduce artificial anisotropy into isotropic 2D materials to deliver polarization-sensitive performance. However, those methods have not been widely promoted because of technical limitations. This paper reports on the successful modulation to the structural symmetry of WSe2 through van der Waals (vdW) interlayer coupling. Correspondingly, both the polarized Raman and photoluminescence (PL) spectra of WSe2 in heterostructure exhibit periodic variation tendency. Similarly, direction-sensitive electronic transport has also been observed in WSe2/CrOCl heterostructure, and the conductance along armchair direction is approximate to 1.5 times of that along zigzag direction. As a functional illustration to the interlayer coupling induced linear dichroism, angle-dependent photodetection is conducted to WSe2/CrOCl device. With light irradiation at 532 nm, the device photocurrent along armchair direction is 1.27 times higher than that along zigzag direction. The abnormal linear dichroism of WSe2 in the study clearly proves that few-layer WSe2 on CrOCl flake has been entitled with artificial anisotropy. The interlayer coupling method is feasible and practical in 2D-material range, offering the possibility to develop polarization-dependent electronic, pyroelectric, and photoelectric devices from isotropic 2D materials.