Axis-selective photoresponse enhancement in NbS3 through pressure-modulated in-plane anisotropic bond alignment

Abstract

Anisotropic photodetection has emerged as a pivotal branch of modern optoelectronics because it directly probes the intrinsic directionality of photogenerated carrier transport in materials, with its advancement depending critically on performance optimization in anisotropic semiconductors. However, most existing anisotropic materials are constrained by rigid atomic arrangements, which limit the tunability of anisotropic photoresponse. Here, we demonstrate an effective strategy that achieves remarkable axis-selective photoresponse enhancement through pressure-modulated in-plane anisotropic bond alignment in NbS3. Unlike previous optimization strategies that focused on modifying surface optical pathways for modest improvements, our approach enables deep modulation of internal electronic structure and anisotropic carrier transport characteristics. In situ high-pressure photoelectric measurements reveal a 53-fold enhancement of photoresponsivity along the a-axis at 7.1 GPa, substantially exceeding the 16-fold improvement along the b-axis. The pressure-driven axial preference arises from a larger modulation amplitude of S–S bond alignment along the a-axis, compared with Peierls distortion suppression of Nb–Nb bond along the b-axis. This effectively enhances electronic coupling of the a-axis component, thereby promoting axis-selective transport of photogenerated carriers. Our findings establish anisotropic bond alignment modulation as an effective paradigm for enhancing axis-selective photoresponse and provide new insights for designing advanced anisotropic photodetectors with tunable performance.