2D AgTiPS₆: a Cross-Stacked In-Plane Anisotropic Semiconductor for Broadband and Polarization-Sensitive Photodetection.

Abstract

2D anisotropic materials, typically consisting of 1D distorted chains arranged in parallel or anti-parallel patterns, are gaining attention for their potential in anisotropic electronic and optoelectronic devices. 2D anisotropic materials with cross-stacked interconnected 1D chains will show improved anisotropy and stability. Nonetheless, to date, no 2D anisotropic materials featuring cross-stacked motifs have been experimentally realized. This work identifies AgTiPS₆ atomic layers, the 2D in-plane anisotropic material with cross-stacked structural motifs, as an n-type semiconductor with a 1.0 eV band gap. Significantly, the unique cross-stacked configuration of 2D AgTiPS₆ results in a significant in-plane anisotropy, with electrical and optoelectrical anisotropies measuring 5.44 and 2.44, respectively, as well as an axially orientation selectivity. Meanwhile, a broadband response from visible (Vis, 405 nm) to middle infrared (MIR, 10.6 µm) is achieved in the AgTiPS₆-based photodetector, with the photoresponse above the bandgap attributed to photothermoelectric effect. Furthermore, 2D AgTiPS₆ has demonstrated environmental stability exceeding 12 months and a laser damage threshold exceeding 10 W cm^- ², attributed to its extra-thick monolayer (1.32 nm). This work introduces a novel in-plane anisotropic material, expanding the repertoire of 2D anisotropic materials and offering potential for the development of anisotropic electronic and optoelectronic devices.