Circular SnS_0.5Se_0.5 Nanosheets with Highly Anisotropic Performance for Nanoelectronics

As we know, binary two-dimensional (2D) IV_A–VI_A monochalcogenides such as stannous sulfide (SnS) and stannous selenide (SnSe) possess an asymmetric crystalline structure perpendicular to the layer-by-layer direction, leading to the potential application in polarization detection, integrated digital inverters, and optoelectronics. In recent years, alloy engineering has drawn researchers’ attention because of the tunable band gap, carrier transport, and other specific characteristics. However, the in-plane anisotropic electrical and optoelectrical performances of 2D SnS_1–xSe_x have been rarely reported. In this paper, a representative content of ultrathin SnS_0.5Se_0.5 circular nanosheets (an optical band gap of ∼ 1.09 eV) has been synthesized successfully by improved low-pressure physical vapor deposition with computational fluid dynamics simulation analysis. Angle-resolved polarized Raman spectroscopy is used to confirm the strong phonon vibration orientation along the armchair (AC) direction. Furthermore, the angle-dependent electrical and photoconductivity results demonstrated that the recorded highest conductivity (σ_zigzag/σ_armchair = ∼19) and mobility (μ_zigzag/μ_armchair = ∼6.87) can be achieved because of the alloying-induced in-plane asymmetry and the rounded shape without etching. Record-high values are reported for SnS, SnSe, and other low asymmetric materials. Last, polarization-sensitive detection is also achieved and exhibits a largest photocurrent under 1064 nm linear light along the AC direction, which is located nearly at the indirect band gap of SnS_0.5Se_0.5. The excellent anisotropic properties of ultrathin SnS_0.5Se_0.5 circular nanosheets indicate further improvement via the van der Waals heterostructure and variable composition design for digital inverters, high-contrast imaging, etc.