Two-Step Synthesis of Large-Area 2D Bi2S3 Nanosheets Featuring High In-Plane Anisotropy

2D materials with high in-plane anisotropy are rapidly emerging as a tantalizing class of nanomaterials with promising applications in nanoelectronics and optoelectronics since they provide an additional degree of freedom that can be exploited in device design. The large-area synthesis of such materials remains however challenging since the anisotropic crystal structure renders identifying a suitable growth substrate to be difficult, while the nanosheets are usually too fragile for the exfoliation and transfer of macroscopic sheets. This work reports the scalable synthesis of highly crystalline, large-area 2D Bi2S3 nanosheets using a novel liquid-metal-based synthesis approach. Ultrathin bismuth oxide sheets are exfoliated from molten bismuth followed by tube furnace sulfurization. The strategy effectively separates the formation of layered structures from the process of anisotropic crystallization, overcoming the shortcomings of established techniques. The synthesized nanosheets feature a highly anisotropic orthorhombic crystal structure with intraplane van der Waals gaps and a direct bandgap of ≈2.3 eV. The nanosheets are found to be highly photoconductive with a photoresponsivity of 8 A W−1. Bi2S3 channel-based field effect transistors feature a maximum hole mobility of 28 cm2 V−1 s−1, highlighting the excellent electronic properties of the isolated nanosheets.