Raman Anisotropy and Polarization-Sensitive Photodetection in 2D Bi 2 O 2 Se-WSe 2 Heterostructure.

Two-dimensional (2D) bismuth oxyselenide (Bi 2 O 2 Se) has attracted increasing attention due to its high mobility, tunable band gap, and air stability. The surface reconstruction of cleaved Bi 2 O 2 Se due to the electrostatic interlayer interactions can lead to the in-plane anisotropic structure and physics. In this work, we first discovered the strong anisotropy in phonon modes through the angle-resolved polarized Raman (ARPR) spectra. Benefiting from the anisotropic feature, a high-performance polarization-sensitive photodetector has been achieved by constructing a heterostructure composed of the multilayer Bi 2 O 2 Se as polarized-light sensitizers and 2D WSe 2 as a photocarrier transport channel. The detectors exhibit broadband response spectra from 405 to 1064 nm along with high responsivity, fast speed, and high sensitivity owing to the photogating effect in this device architecture. More importantly, the photocurrent shows strong light polarization dependence with the maximum dichroism ratio of 4.9, and a reversal is observed for the angle-dependent photocurrent excited by polarized 405 and 635 nm light. This work provides new insight in terms of optical and photocurrent anisotropy of exfoliated Bi 2 O 2 Se and expands its applications in angle-resolved electronics and optoelectronics.