Growth of Ultrathin Ternary Teallite (PbSnS2) Flakes for Highly Anisotropic Optoelectronics

Two-dimensional (2D) ternary materials have gained significant attention because of their additional degree of freedom stemming from the variable stoichiometry. However, the research on 2D ternary materials is still in the early stage because of the difficulty of synthesizing them. Here, ultrathin PbSnS2 flakes are synthesized via chemical vapor deposition (CVD) assisted by salt and a molecular sieve with thickness down to similar to 2.4 nm. Adding salt and a molecular sieve results in lowering of the melting point of metal precursors and uniformly distributed source vapors in the reaction system, respectively. Impressively, 2D PbSnS2 flake shows giant anisotropic mobility (mu(armchair)/mu(zigzag) = 1.78) and responsivity (R-zigzag/R-armchair 1.25). The employment of salt and a molecular sieve in the CVD process for successful synthesis of ultrathin PbSnS2 flakes may provide a new platform for the design of other 2D ternary materials.