Realization of 2D crystalline metal nitrides via selective atomic substitution.

Two-dimensional (2D) transition metal nitrides (TMNs) are new members in the 2D materials family with a wide range of applications. Particularly, highly crystalline and large area thin films of TMNs are desirable for applications in electronic and optoelectronic devices; however, the synthesis of these TMNs has not yet been achieved. Here, we report the synthesis of few-nanometer thin MoN crystals with large area and high quality via in situ chemical conversion of layered MoS crystals. The versatility of this general approach is demonstrated by expanding the method to synthesize WN and TiN. Our strategy offers a new direction for preparing 2D TMNs with desirable characteristics, opening a door for studying fundamental physics and facilitating the development of next-generation electronics.