Synthesis of Ultrathin FeS Nanosheets via Chemical Vapor Deposition

Fe-based 2D materials exhibit rich chemical compositions and structures, which may imply many unique physical properties and promising applications. However, achieving controllable preparation of ultrathin non-layered FeS crystal on SiO₂/Si substrate remains a challenge. Herein, the influence of temperature and molecular sieves is reported on the synthesis of ultrathin FeS nanosheets with a thickness as low as 2.3 nm by molecular sieves-assisted chemical vapor deposition (CVD). The grown FeS nanosheets exhibit a non-layered hexagonal NiAs structure and belong to the P6₃/mmc space group. The inverted symmetry broken structure is confirmed by the angle-resolved second harmonic generation (SHG) test. In particular, the 2D FeS nanosheets exhibit exceptional metallic behavior, with conductivity up to 1.63 × 10⁶ S m^-1 at 300 K for an 8 nm thick sample, which is higher than that of reported 2D metallic materials. This work provides a significant contribution to the synthesis and characterization of 2D non-layered Fe-based materials.