Anisotropic photoresponse of layered 2D SnS-based near infrared photodetectors

We fabricated near-infrared (NIR) photodetectors with two-dimensional (2D) single crystal orthorhombic SnS nanosheets. The as-fabricated devices exhibited an excellent photoresponsivity of 365 A W^-1 under 808 nm light illumination with an excellent external quantum efficiency of 5.70 × 10⁴, which can be further increased to 635 A W^-1 and 9.92 × 10⁴ by Au nanoparticle decoration. An anisotropic photoresponse was found for the SnS-based NIR photodetectors and the conductivity and photoconductivity along the zigzag direction are much greater than those along the armchair direction. Treated with oxygen plasma, the effects of defects on the anisotropic photoresponse were further investigated. These results provide a deeper understanding of the electrical and photoelectrical properties of 2D SnS nanosheet based devices.