In-situ Generated Volatile Precursor for CVD Growth of a Semimetallic 2D Dichalcogenide.

Semimetallic layered transition metal dichalcogenides, such as TiS, can serve as a platform material for exploring novel physics modulated by dimensionality, as well as for developing versatile applications in electronics and thermoelectrics. However, controlled synthesis of ultrathin TiS in a dry-chemistry way has yet to be realized because of the high oxophilicity of active Ti precursors. Here we report an ambient pressure chemical vapor deposition (CVD) method to grow large-size, highly crystalline 2D TiS nanosheets through in-situ generating titanium chloride as the gaseous precursor. The addition of NHCl promoter can react with Ti powders and switch the solid-phase sulfurization reaction into a CVD process, thus enabling the controllability over the size, shape, and thickness of the TiS nanosheets via tuning the synthesis conditions. Interestingly, this semimetallic 2D material exhibits near-infrared surface plasmon resonance absorption and a memristor-like electrical behavior, both holding promise for further application developments. Our method hence opens a new avenue for the CVD growth of moisture- and oxygen-sensitive 2D metal dichalcogenides directly from metal powders and pave the way for exploring their intriguing properties and applications.