Ultra-high anisotropy and electronic property of two-dimensional PbSnS₂ with a black phosphorus structure

Novel two-dimensional materials with fascinating electronic structures hold promise for applications in electronics, optoelectronics, and sensor devices. In this work, the mechanical, anisotropic, and electronic properties of PbSnS₂ monolayer, which adopts a black-phosphorus-like structure, were systematically investigated using density functional theory calculations. The PbSnS₂ monolayer is identified as an indirect band gap semiconductor. The band gap is predicated to be 1.22 eV and 1.69 eV by PBE functional and HSE06 methods, respectively. Notably, it exhibits a high anisotropic carrier mobility as μ_e = 4.46 × 10³ cm²⋅V⁻¹⋅s⁻¹ with electrons preferentially transporting along the zigzag direction. The band gap can be effectively narrowed under the strains in the armchair direction whereas enlarged in the zigzag direction. In addition, PbSnS₂ monolayer exhibits strong optical absorption in visible-light and ultra-visible regions. Our findings suggest that the ultra-high anisotropy in both carrier mobility and optical absorption makes PbSnS₂ monolayer a promising candidate for applications in unipolar field-effect transistors and photosensitive devices. This study provides valuable insights for future exploration of low-dimensional materials with tailored functionalities.